Newly diagnosed ANCA-associated vasculitis after COVID-19 infection: a case report.

BACKGROUND: Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis is a systemic autoimmune disease characterized by mononuclear cell infiltration and small and medium-sized blood vessel destruction leading to renal failure. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been shown to have the potential to induce the presentation or exacerbation of autoimmune disease. This report describes the clinical features of a case of newly diagnosed ANCA-associated vasculitis after COVID-19 Infection. CASE PRESENTATION: During the COVID-19 pandemic, a 67- year-old female Japanese was undergoing treatment for interstitial pneumonia, diabetes mellitus, and hypertension at her local doctor. About 2 months ago, she was diagnosed with COVID-19 and went to a hotel for treatment, and her condition improved. But a month later, after her COVID-19 infection, she presented with a fever and cough and visited Yodogawa Christian Hospital in Osaka, Japan. The reverse transcription-polymerase chain reaction was negative. She underwent extensive radiological and laboratory investigations. Serologies revealed a high perinuclear-ANCA titer with a specific anti-myeloperoxidase antibody titer of 31.7 units/mL. We suspected ANCA-associated vasculitis and performed a renal biopsy. Renal biopsy showed evidence of crescentic glomerulonephritis, which was consistent with ANCA-associated vasculitis. The patient was referred to the Department of Rheumatology and Clinical Immunology for steroid pulse and cyclophosphamide treatment. CONCLUSIONS: Delayed screening may lead to progression of the autoimmune disease, so prompt diagnosis is necessary. In this case, we could make an immediate diagnosis and refer the patient to the Department of Rheumatology and Clinical Immunology.

[Autoimmune hemolytic anemia complicated with acute kidney injury and tubulopathy due to hemoglobin casts].

A 62-year-old male patient was admitted for close monitoring of anemia (hemoglobin level, 8.2 g/dl). Hemolytic anemia was observed; however, the direct antiglobulin test (DAT) result (standard tube method) was negative. Nevertheless, autoimmune hemolytic anemia (AIHA) was still suspected; therefore, a DAT (Colum method) and quantifying levels of red-blood-cell bound immunoglobulin G were performed, resulting in a definite diagnosis of warm AIHA. The patient also had an acute kidney injury (AKI) from the time of admission, which was poorly improved by supplemental fluids therapy alone. Therefore, renal biopsy was performed. Renal biopsy revealed acute tubular injury due to hemoglobin columns, and a diagnosed AKI caused by hemolysis due to AIHA. Following the definitive diagnosis of AIHA, the patient was treated with prednisolone, and after approximately 2 weeks, the anemia and nephropathy completely improved, which is maintained to this day. We report this case as a rare case of AKI induced by hemolysis of AIHA and a successful case of renal salvage by early administration of steroid.

Thrombotic thrombocytopenic purpura developed during the conservative treatment of anti-phospholipase A2 receptor antibody-positive idiopathic membranous nephropathy: a case report.

BACKGROUND: Idiopathic membranous nephropathy (MN) is one of the major glomerulonephritis that cause nephrotic syndrome. The phospholipase A2 receptor (PLA2R) has recently been identified as an endogenous antigen of idiopathic MN. Thrombotic thrombocytopenic purpura (TTP) is a disorder characterized by schistocytes, hemolytic anemia, thrombocytopenia, and organ dysfunction which occurs as a result of thrombi. Patients with acquired TTP have autoantibodies against a disintegrin and metalloprotease with thrombospondin type 1 motif 13 (ADAMTS13). These autoantibodies act as an inhibitor and cause ADAMTS13 deficiency. Idiopathic MN and acquired TTP are usually considered as independent autoimmune diseases. We experienced a patient who developed TTP during the conservative treatment of idiopathic MN, with the coexistence of ADAMTS13 inhibitor and anti-PLA2R antibody. CASE PRESENTATION: A 73-year-old man presented with thrombocytopenia, hemolytic anemia, disturbance of consciousness, and acute kidney injury after 4-year course of biopsy-proven idiopathic MN. ADAMTS13 activity was undetectable and the ADAMTS13 inhibitor was identified. Additionally, he was positive for anti-PLA2R antibody. The patient did not have any diseases that could cause secondary thrombotic microangiopathy, and he was diagnosed with acquired TTP. Steroid therapy and plasma exchange were initiated and the acquired TTP resolved. MN achieved remission 3 months after the anti-PLA2R antibody disappeared. CONCLUSIONS: This is the first reported case of acquired TTP developed during conservative treatment of idiopathic MN, with both ADAMTS13 inhibitor and anti-PLA2R antibody positive at the onset of the TTP. The present case suggests that idiopathic MN might be associated with the development of some cases of acquired TTP.

Serum phosphate levels modify the impact of parathyroid hormone levels on renal outcomes in kidney transplant recipients.

Separate assessment of mineral bone disorder (MBD) parameters including calcium, phosphate, parathyroid hormone (PTH), fibroblast growth factor 23 (FGF23), 25-hydroxyvitamin D, and 1,25-dihydroxyvitamin D (1,25D) predict renal outcomes in kidney transplant recipients (KTRs), with conflicting results. To date, data simultaneously evaluating these parameters and interwoven relations on renal outcomes are scarce. We conducted a prospective long-term follow-up cohort study included 263 KTRs with grafts functioning at least 1 year after transplantation. The outcome was a composite of estimated GFR halving and graft loss. Cox regression analyses were employed to evaluate associations between a panel of six MBD parameters and renal outcomes. The outcome occurred in 98 KTRs during a median follow-up of 10.7 years. In a multivariate Cox analysis, intact PTH (iPTH), phosphate, and 1,25D levels were associated with the outcome (hazard ratio, 1.60 per log scale; 95% confidence interval, 1.19-2.14, 1.60 per mg/dL; 1.14-2.23 and 0.82 per 10 pg/mL; 0.68-0.99, respectively). Competing risk analysis with death as a competing event yielded a similar result. After stratification into four groups by iPTH and phosphate medians, high risks associated with high iPTH was not observed in KTRs with low phosphate levels (P-interaction < 0.1). Only KTRs not receiving active vitamin D, poor 1,25D status predicted the worse outcome (P-interaction < 0.1). High iPTH, phosphate, and low 1,25D, but not FGF23, levels predicted poor renal outcomes. Simultaneous evaluation of PTH and phosphate levels may provide additional information regarding renal allograft prognosis.

Magnesium modifies the association between serum phosphate and the risk of progression to end-stage kidney disease in patients with non-diabetic chronic kidney disease.

It is known that magnesium antagonizes phosphate-induced apoptosis of vascular smooth muscle cells and prevents vascular calcification. Here we tested whether magnesium can also counteract other pathological conditions where phosphate toxicity is involved, such as progression of chronic kidney disease (CKD). We explored how the link between the risk of CKD progression and hyperphosphatemia is modified by magnesium status. A post hoc analysis was run in 311 non-diabetic CKD patients who were divided into four groups according to the median values of serum magnesium and phosphate. During a median follow-up of 44 months, 135 patients developed end-stage kidney disease (ESKD). After adjustment for relevant clinical factors, patients in the lower magnesium-higher phosphate group were at a 2.07-fold (95% CI: 1.23-3.48) risk for incident ESKD and had a significantly faster decline in estimated glomerular filtration rate compared with those in the higher magnesium-higher phosphate group. There were no significant differences in the risk of these renal outcomes among the higher magnesium-higher phosphate group and both lower phosphate groups. Incubation of tubular epithelial cells in high phosphate and low magnesium medium in vitro increased apoptosis and the expression levels of profibrotic and proinflammatory cytokine; these changes were significantly suppressed by increasing magnesium concentration. Thus, magnesium may act protectively against phosphate-induced kidney injury.

Comparison of methylprednisolone plus prednisolone with prednisolone alone as initial treatment in adult-onset minimal change disease: a retrospective cohort study.

BACKGROUND AND OBJECTIVES: Previous studies suggested that intravenous methylprednisolone possibly accelerates remission of proteinuria in adult-onset minimal change disease; its impact on relapse of proteinuria is unknown. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: This multicenter retrospective cohort study included 125 adult-onset minimal change disease patients diagnosed by kidney biopsy between 2000 and 2009 and treated initially with corticosteroid in five nephrology centers in Japan participating in the Study of Outcomes and Practice Patterns of Minimal Change Disease. Times to first remission and first relapse of proteinuria after initiating the first immunosuppressive therapy were compared between 65 patients with initial use of intravenous methylprednisolone followed by prednisolone and 60 patients with initial use of prednisolone alone using multivariate Cox proportional hazards models. After calculating the probability of receiving methylprednisolone and prednisolone using a logistic regression model (propensity score), the results were ascertained using propensity score-matched and -stratified models. RESULTS: During the median 3.6 years of observation (interquartile range=2.0-6.9), all 65 patients in the methylprednisolone and prednisolone group achieved remission within 11 (8-20) days of the corticosteroid initiation, whereas in the prednisolone group, 58 of 60 patients (96.7%) achieved remission within 19 (12-37) days (P<0.001). After achieving first remission, 32 (49.2%) patients in the methylprednisolone and prednisolone group and 43 (74.1%) patients in the prednisolone group developed at least one relapse. Multivariate Cox proportional hazards models revealed that methylprednisolone and prednisolone use was significantly associated with early remission (multivariate-adjusted hazard ratio, 1.56; 95% confidence interval, 1.06 to 2.30) and lower incidence of relapse (0.50; 95% confidence interval, 0.29 to 0.85) compared with prednisolone use alone. These results were ascertained in propensity score-based models. No significant difference was observed in incidence of adverse events, including infection, aseptic osteonecrosis, cataract, diabetes, and gastrointestinal bleeding. CONCLUSIONS: Initial use of methylprednisolone was associated with earlier remission and lower incidence of relapse in adult-onset minimal change disease patients. Efficacy of methylprednisolone should be evaluated in randomized controlled trials.

Multidetector-row computed tomography is useful to evaluate the therapeutic effects of bisphosphonates in glucocorticoid-induced osteoporosis.

Osteoporosis is one of the major complications of glucocorticoid therapy. Osteoporosis is usually defined by the levels of bone mineral density (BMD) assessed by dual energy X-ray absorptiometry (DEXA); however, glucocorticoids often induce fractures in patients with normal BMD. Thus, novel diagnostic approaches are required. In this study, we examined whether multidetector-row computed tomography (MDCT) is useful to assess the bone status in glucocorticoid-induced osteoporosis (GIO). Because bisphosphonates have been proven to prevent bone fracture in GIO, we tried to detect the therapeutic effects of bisphosphonates in GIO by MDCT. Fifteen Japanese patients with immunoglobulin A nephropathy who had normal renal function were enrolled in this open-label randomized trial. Patients were randomly divided into three groups-calcitriol (VD), menatetrenone (VK), or bisphosphonate (Bis). Bone conditions were analyzed twice by three different methods-bone turnover markers, DEXA, and MDCT-at the start and 6 months after the start of therapy. Both bone markers and DEXA could not detect significant differences among the therapeutic groups; however, MDCT-based analyses detected the preventive effects of bisphosphonates in GIO. Compared to VD, Bis improved structural indices, such as bone volume fraction, trabecular separation, marrow star volume, and structure model index whereas the difference between VD and VK was not significant. Finite element analysis revealed that simulated fracture load in the Bis group was significantly improved. These findings suggested that MDCT-based assessment is superior to bone markers and/or DEXA in assessing the therapeutic effect of bisphosphonates on GIO.

Vitamin D deficiency predicts decline in kidney allograft function: a prospective cohort study.

CONTEXT: Vitamin D, often deficient in kidney transplant (KTx) recipients, has potential immunomodulatory effects. OBJECTIVE: This study aimed to evaluate whether vitamin D status affects the rate of decline in kidney allograft function. DESIGN, SETTING, AND PATIENTS: The study included a prospective cohort of 264 ambulatory KTx recipients at a single Japanese center. MAIN OUTCOME MEASURES: We measured the baseline 25-hydroxyvitamin D (25D) concentration and examined its association with annual decline in estimated glomerular filtration rate (eGFR). Secondary outcome was rescue treatment with iv methylprednisolone (IV-MP) as an index of rejection episodes. RESULTS: The mean serum 25D concentration was 17.1 (SD 6.5) ng/mL, and 68.4% patients had vitamin D inadequacy or deficiency. Time after KTx was a significant effect modifier for the association of serum 25D concentration with annual eGFR change and need for IV-MP (P for interaction < .1). We divided patients according to the median time after KTx (10 y) and found that low vitamin D was significantly associated with a rapid eGFR decline at less than 10 years after KTx but not at 10 or more years after KTx. The same was true for rescue treatment with IV-MP. Overall, propensity score matching showed independent associations of low vitamin D with both outcomes. Stratified matching confirmed pronounced associations at less than 10 years after KTx. CONCLUSIONS: Vitamin D deficiency predicts a rapid decline in eGFR and need for IV-MP at less than 10 years after KTx. Future studies are warranted to evaluate the clinical efficacy of vitamin D supplementation.

Association of nocturnal hypoxemia with progression of CKD.

BACKGROUND AND OBJECTIVES: Nocturnal hypoxemia is highly prevalent among patients with CKD. Nocturnal hypoxemia contributes to systemic inflammation, oxidative stress, endothelial cell dysfunction, and activation of the renin-angiotensin system, which are common pathologic mechanisms of CKD progression. This study investigated whether nocturnal hypoxemia is independently associated with CKD progression. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: This two-center retrospective cohort study included 161 patients with stages 3-4 CKD enrolled from January of 2009 to July of 2011 with a body mass index less than 25.0 kg/m(2). The 4% oxygen desaturation index, the number of events per hour in which oxygen saturation decreases by >4% during sleep, was measured, and the declining rate of the estimated GFR was followed over 1 year. The severity of nocturnal hypoxemia was categorized as none (oxygen desaturation index<5.0), mild (5.0≤oxygen desaturation index<15.0), or moderate to severe (15.0≤oxygen desaturation index). RESULTS: The mean estimated GFR of the total cohort at baseline was 31 ml/min per 1.73 m(2). Eighty patients (49.7%) were diagnosed with nocturnal hypoxemia; 64 patients were diagnosed with mild nocturnal hypoxemia, and 16 patients were diagnosed with moderate-to-severe nocturnal hypoxemia. The estimated GFR declined three- to fourfold faster in patients with moderate-to-severe nocturnal hypoxemia than patients with no or mild nocturnal hypoxemia (the mean values [95% confidence intervals] were -2.14 [-1.06 to -3.21], -3.02 [-1.31 to -4.74], and -8.59 [-2.00 to -15.2] ml/min per 1.73 m(2) per year in the no, mild, and moderate-to-severe nocturnal hypoxemia groups, respectively; P=0.003). Nocturnal hypoxemia remained a significant predictor of decline in estimated GFR after adjustment for various baseline clinical factors. CONCLUSIONS: In nonobese patients with CKD, nocturnal hypoxemia is an independent risk factor of a rapid decline in kidney function.

Age and prediction of remission and relapse of proteinuria and corticosteroid-related adverse events in adult-onset minimal-change disease: a retrospective cohort study.

BACKGROUND: In adult-onset minimal-change disease (MCD) the predictors of remission and relapse of proteinuria and corticosteroid-related adverse events remain unknown. METHODS: The multicenter retrospective cohort study, the STudy of Outcomes and Practice patterns of Minimal-Change Disease (STOP-MCD), included 142 adult-onset MCD patients in 5 nephrology centers in Japan. Primary outcomes were first remission of proteinuria defined by urinary protein (UP) <0.3 g/day, UP/creatinine ratio (UPCR) <0.3, and/or negative/trace by dipstick test and first relapse of proteinuria defined by UP ≥1.0 g/day, UPCR ≥1.0, and/or dipstick test ≥1+ followed by immunosuppressive therapy. Secondary outcomes were corticosteroid-related adverse events. RESULTS: During the median 3.6 (interquartile range, 2.0-6.9) years of the entire observational period, 136 (95.8 %) and 79 (58.1 %) patients developed at least 1 remission and 1 recurrence within a median of 15 (10-34) days and 0.90 (0.55-1.57) years, respectively. Compared with younger patients aged 15-29 years at kidney biopsy, elderly patients aged ≥60 years developed remission significantly later [hazard ratio 0.53 (95 % confidence interval 0.32-0.88)], while older patients aged ≥45 years were at a significantly lower risk of relapse [45-59 years, 0.46 (0.22-0.96); 60-83 years, 0.39 (0.21-0.74)]. However, older patients were significantly more vulnerable to severe infection, diabetes, and cataract as compared with younger patients. CONCLUSION: Younger patients had a higher risk of relapse while older patients had a lower risk of relapse but a higher risk of corticosteroid-related adverse events.

Fatal hypermagnesemia induced by preoperative colon preparation in an elderly woman: report of a case.

An 85-year-old woman with rectal carcinoma was referred to our hospital for surgical treatment. She had a history of constipation treated with oral magnesium oxide. She received 34 g of magnesium citrate (Magcolol P(®)) orally for 2 days as a mechanical bowel preparation prior to the operation. Just before the operation, she suddenly developed nausea, vomiting, and cyanosis and went into cardiac arrest. Despite support by mechanical ventilation, dopamine, dobutamine, and norepinephrine, she exhibited repeated bradycardia that was nearly fatal and required temporary pacing. The following day, her laboratory tests revealed marked hypermagnesemia (14.3 mg/dL). After a hemodialysis session, she recovered dramatically and all vasopressors were withdrawn. We conclude that preoperative mechanical bowel preparation with magnesium-containing cathartics can cause fatal hypermagnesemia in elderly patients even if their renal function is normal.

Fibroblast growth factor 23 and 25-hydroxyvitamin D levels are associated with estimated glomerular filtration rate decline.

The combination of serum 25-hydroxyvitamin D (25D) and fibroblast growth factor 23 (FGF23) levels predict hard renal outcomes in patients with chronic kidney disease (CKD), independent of classical markers of mineral and bone disorders, including serum phosphorus, parathyroid hormone, 1,25-dihydroxyvitamin D levels, and active vitamin D therapy. In a prospective cohort study of 738 Japanese pre-dialysis outpatients with CKD, we examined potentially non-linear associations between 25D and FGF23 levels and estimated glomerular filtration rate (eGFR) changes in 727 patients with at least a 6-month observation period and no history of admission by acute kidney injury. We used multiple regression analyses with restricted cubic spline functions using annualized eGFR decline as a dependent variable. A significantly non-linear positive relationship between 25D and eGFR changes was observed. The annualized eGFR decline was greater in patients with 25D concentrations <25 and 23 ng/ml in univariate and multivariate analyses, respectively. Above this threshold, the eGFR decline plateaued. FGF23 showed a linear negative association with eGFR changes. After dividing the patients into four groups according to median 25D and FGF23 levels, the annualized eGFR changes in the Low FGF23-Low 25D, High FGF23-High 25D, and High FGF23-Low 25D groups were 0.49 (95% confidence intervals: -2.83 to 3.81), -1.24 (-5.00 to 2.52), -4.77 (-8.85 to -0.69), respectively, relative to the Low FGF23-High 25D group (P for trend, 0.02). Thus, combined use of FGF23 and 25D is useful to predict eGFR change in patients with CKD as well as hard renal outcomes.

Orally active vitamin d for potential chemoprevention of posttransplant malignancy.

Posttransplant malignancy (PTM) is a limiting factor both for patient and allograft survival in kidney transplant recipients (KTRs). We hypothesized that active vitamin D compounds (AVD) could reduce PTM development in KTRs. Ambulatory KTRs in a Japanese prospective cohort were followed from August 2007 to November 2010. The outcome of interest was newly diagnosed PTM. A propensity score (PS) of having received AVDs was estimated using 26 clinically relevant factors. We used the Cox proportional hazards model with stratification by PS tertiles on the assumption that baseline hazard functions differ among tertiles. As sensitivity analyses, we used inverse probability weighting and PS matching. Among 218 participants, the median age was 50 (interquartile range [IQR], 40 to 59) years, 63.3% were male, median time since transplantation was 11.2 (IQR, 5.2 to 17.1) years, and mean estimated GFR was 41.3 (SD, 15.6) mL/min per 1.73 m(2). At baseline, 42.2% had been treated with AVDs mainly for glucocorticoid-induced osteoporosis. AVDs used were calcitriol (58.7%) and alfacalcidol (41.3%). During follow-up, PTM developed in 5.4% of 92 AVD users and 8.7% of 126 nonusers. Poor vitamin D status was common in the participants, but the serum 25-hydroxyvitamin D level was not significantly associated with PTM in Cox regression analysis. After stratifying patients by PS tertiles, we found that AVDs were significantly associated with a lower risk of PTM (HR 0.25 [0.07 to 0.82]). Sensitivity analyses yielded similar results. AVDs are potential chemopreventive agents against PTM in KTRs.

Dialysis vintage and parathyroid hormone level, not fibroblast growth factor-23, determines chronic-phase phosphate wasting after renal transplantation.

PURPOSE: Fibroblast growth factor 23 (FGF23), rather than parathyroid hormone (PTH), has been shown to be the major factor behind hypophosphatemia in the early period after renal transplantation. However, it is not clear whether phosphate wasting persists in the chronic phase. Purpose of our study is to elucidate whether FGF23 can also explain phosphate wasting, if any, in the chronic phase. METHODS: In this cross-sectional observational study, we enrolled 247 recipients who had received a graft more than 1 year prior to this study. We compared the phosphate metabolism of recipients and predialysis chronic kidney disease (CKD) patients who are matched on age and estimated glomerular filtration rate (eGFR). We also investigated the determinants of tubular reabsorption of phosphate normalized for glomerular filtration rate (TmP/GFR), as an index of renal threshold for phosphate. RESULTS: Recipients had a median dialysis vintage of 27.0 months and eGFR 41.2 mL/min/1.73 m(2). Whereas hypophosphatemia (<2.4 mg/dL) was observed in 6.1% of the recipients, 55.2% had TmP/GFR lower than 2.4 mg/dL. Recipients showed significantly lower TmP/GFR in all CKD stages than their predialysis counterparts, indicating that phosphate wasting persists in the chronic phase. Compared to predialysis patients, the recipients in stages 2T and 3T showed lower phosphate and higher intact PTH levels, despite a higher percentage being active vitamin D users. However, in stage 4T, phosphate retention masked relative hypophosphatemia. FGF23 was higher in the recipients across all CKD stages, but adjustment for vitamin D prescription revealed that transplantation had no effect on FGF23. Multiple regression analysis in the recipients showed significant negative associations of intact PTH and dialysis vintage with TmP/GFR. CONCLUSIONS: Renal phosphate wasting persists in the chronic-phase renal transplantation recipients even with normophosphatemia. Persistent hyperparathyroidism and longer dialysis vintage, not FGF23, was associated with renal phosphate wasting in the chronic phase. Such an impact on phosphate metabolism of the factors determined in dialysis period could be called as "uremic memory". This novel finding in the chronic phase is in sharp contrast to the previous finding in the early phase that FGF23 levels are determinants of phosphate wasting.

Intact fibroblast growth factor 23 levels predict incident cardiovascular event before but not after the start of dialysis.

PURPOSE: Low 25-hydroxyvitamin D (25D), increased levels of fibroblast growth factor 23 (FGF23), parathyroid hormone (PTH), and alkaline phosphatase (ALP) were reported to be risk factors for mortality in chronic kidney disease (CKD). However, the independent associations of these factors with cardiovascular disease (CVD), the leading cause of death among CKD patients, remain unclear. Our purpose was to identify which of these factors predict incident CVD in CKD. METHODS: In this prospective cohort study, we enrolled 738 predialysis outpatients in the two nephrology departments. We employed Cox proportional hazards analyses to elucidate predictors of the endpoint, defined as fatal or non-fatal cardiovascular event requiring hospitalization. Multiple imputation was performed for missing values. RESULTS: Mean estimated glomerular filtration rate (eGFR) was 35 mL/min/1.73 m(2). During a median duration of 4.4 years, 86 patients developed the endpoint, of whom 62 patients achieved it before the initiation of dialysis. Multivariable analyses revealed that high serum intact FGF23 levels predicted the outcome preceding dialysis initiation (hazard ratio (HR) per lnFGF23 (SD), 1.64 (1.27-2.30)), while 25D, PTH, and bone-specific ALP did not. Adding FGF23 to the conventional model of age, sex, diabetes, prior CVD, pulse pressure, and eGFR, led to a net reclassification improvement of 6.87% (P=0.04). Not censoring the patients at the start of dialysis and continuing follow-up even after dialysis, FGF23 levels did not predict the outcome (HR, 1.16 (0.91-1.48)). Complete case analyses yielded similar results. CONCLUSIONS: Intact FGF23 levels in predialysis CKD predicted incident cardiovascular events requiring hospitalization before starting dialysis, but did not predict events during the entire follow-up period, including post dialysis initiation.

Combined use of vitamin D status and FGF23 for risk stratification of renal outcome.

BACKGROUND AND OBJECTIVES: Hyperphosphatemia, vitamin D deficiency, hyperparathyroidism, and high serum fibroblast growth factor 23 (FGF23) levels, when studied separately, were found to predict the progression of CKD. However, studies with simultaneous measurement of mineral bone disorder (MBD)-related factors were scarce. This study aimed to identify factors predicting renal outcome independent of other factors. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: This was a prospective cohort study of 738 Japanese predialysis outpatients in the nephrology departments of two hospitals. The outcome was defined as a doubling of serum creatinine or initiation of dialysis. RESULTS: Mean estimated GFR (eGFR) was 35 ml/min per 1.73 m(2). At enrollment, the increase in intact FGF23 with decreasing eGFR was the earliest among changes in MBD-related factors, followed by 1,25-dihydroxyvitamin D decrease, parathyroid hormone increase, and phosphate increase. During a median duration of 4.4 years, 213 patients reached the endpoint. In a multivariable Cox model, high FGF23 and low 25-hydroxyvitamin D (25D) levels were the only MBD-related factors associated with a higher risk of renal endpoint (adjusted hazard ratio [95% confidence interval] per unit change of log FGF23 and 10 ng/ml of 25D: 1.83 [1.28-2.61] and 0.61 [0.41-0.90], respectively). There was no significant interaction between 25D and FGF23 (P=0.11). Active vitamin D therapy, serum phosphate, 1,25-dihydroxyvitamin D, and parathyroid hormone levels were not related to the renal endpoint. Treating death as a competing risk or multiple imputation for missing values yielded similar results. CONCLUSIONS: Combined use of two markers is useful for the risk stratification of renal outcome.

Guideline-practice gap in the management of predialysis chronic kidney disease mineral bone disorder in Japan.

No study has reported the current status of the management of chronic kidney disease mineral bone disorder (CKD-MBD) in Japan. Using the Osaka Vitamin D Study in CKD (OVIDS-CKD), we examined the prevalence of patients with serum calcium, phosphate, parathyroid hormone (PTH), or 25-hydroxyvitamin D levels outside the target of KDOQI guidelines. Eighty-four percent of the patients had 25-hydroxyvitamin D <30 ng/mL. Significant determinants of poor vitamin D status were female gender, diabetes, high PTH, and high urinary protein (2+ or greater). The percentage of patients with intact PTH higher than the target was 8% in CKD stage 3a, while between 20-22% in stages 3b to 5. The patients indicated for ergocalciferol were 7, 18, and 19% in stages 3a, 3b, and 4, respectively, and those indicated for active vitamin D were 21% in stage 5. Since neither ergocalciferol nor cholecalciferol is available in 2011 in Japan, we have no choice but to prescribe alfacalcidol or calcitriol; however, the percent of patients receiving these drugs was only 1, 4, 8, and 14% in stages 3a, 3b, 4, and 5, respectively, indicating that PTH and vitamin D status are not well controlled in Japan. In contrast, more than 80% of the patients met the target of serum calcium and phosphate. Contrary to expectations, nearly 20% of the patients had hypophosphatemia in stage 3 and 5, possibly because of strict protein restriction. Given these results, nephrologists should consider prescribing active vitamin D, especially for females and patients with diabetes, massive proteinuria, or secondary hyperparathyroidism.

Fetuin-mineral complex reflects extraosseous calcification stress in CKD.

Fetuin-A is an important inhibitor of extraosseous calcification, but some of the studies that used ELISAs did not identify a significant relationship between serum fetuin-A levels and vascular calcification in patients with chronic kidney disease (CKD). Here, we used centrifugation to separate a fetuin-mineral complex (FMC) composed of fetuin-A, fibrinogen, fibronectin-1, and calcium from the serum of hemodialysis patients. In addition, we analyzed serum fetuin-A levels of 73 patients with diabetes and CKD (predialysis) after centrifugation. Fetuin-A concentrations were significantly lower in supernatants than in serum from patients at any stage of CKD, indicating systemic circulation of FMC in these patients. With greater severity of CKD, the contribution of FMC to total fetuin-A increased. Despite the absence of a correlation between serum fetuin-A and coronary artery calcification scores (CACS), supernatant fetuin-A negatively correlated with CACS and the extent to which centrifugation reduced fetuin-A (reduction ratio [RR]) positively correlated with CACS. In a longitudinal study of 12 hemodialysis patients with secondary hyperparathyroidism, parathyroidectomy and cinacalcet therapy each significantly reduced the RR without changing supernatant fetuin-A levels after 1 month, suggesting a reduction in FMC. Moreover, the magnitude of cinacalcet-induced reduction in parathyroid hormone correlated with the decrease in RR but not with changes in serum or supernatant fetuin-A. These data suggest that a quantitative measure of FMC, not supernatant or serum fetuin-A as measured in previous studies, reflects extraosseous calcification stress.

The impact of diabetes mellitus on vitamin D metabolism in predialysis patients.

Although diabetes mellitus (DM) disturbs bone metabolism, little is known concerning its effects on laboratory abnormalities in chronic kidney disease-mineral and bone disorders (CKD-MBD). We extracted data for 602 patients from the Osaka Vitamin D Study in patients with CKD (OVIDS-CKD), an observational study enrolling predialysis outpatients. No enrolled patients received vitamin D, bisphosphonate, estrogen or raloxifene. We measured 1- 84 PTH, 25-hydroxyvitamin D (25D), calcitriol, fibroblast growth factor-23 (FGF-23), calcium (Ca), and phosphate (P). Since there were 112 DM patients (group D), we extracted 112 age-, sex-, and eGFR-matched non-DM counterparts (group N). We compared biochemical markers between groups, and then performed multiple regression analyses for all 602 subjects to confirm the results obtained. Group D had significantly higher corrected Ca and P than group N throughout all stages of CKD. In group D, 25D decreased as renal function declined, while in group N it remained constant (interaction P<0.05). Despite higher P and poorer vitamin D status in DM, there were no differences in 1- 84 PTH level between group D and group N stratified by stage of CKD, resulting in significantly lower calcitriol levels in group D in late CKD. Multiple regression analyses revealed that DM was significantly associated with low vitamin D status even with adjustment for urinary protein, and that this poorer vitamin D status in DM was responsible for lower calcitriol level associated with DM. Despite higher P, lower FGF-23 in early CKD (stages 1 + 2) and comparable level of FGF-23 in late stages of CKD (stages 3, 4, and 5) were observed in group D. We interpreted these results to indicate that inappropriate production of FGF-23 in DM might explain higher serum phosphate in DM. Multiple regression analysis with adjustment for covariates confirmed an independent relationship between DM and low FGF-23, implying the existence of dysfunction or decreased density of osteocytes in DM. Given the origin of these phosphaturic hormones, DM may thus have markedly deleterious effects on parathyroid and bone. Poorer vitamin D status and higher CaP product might be partly responsible for functional and structural changes of vasculature, respectively, in DM.

Usefulness of bone resorption markers in hemodialysis patients.

Although bone biopsy is a golden standard in the diagnosis of renal osteodystrophy, it is invasive and repetitive evaluation of bone status by this method is practically impossible. Non-invasive evaluation by bone metabolic markers such as serum cross-linked N-telopeptide of type I collagen (NTX) might give us additional information which cannot be obtained only by measurements of parathyroid hormone (PTH). These days, bone resorption marker, serum tartrate-resistant acid phosphatase (TRAP5b) was reported to be correlated with histomorphometric parameters of bone resorption in a bone biopsy study enrolling hemodialysis (HD) patients. In the current study, we studied the correlation of sera NTX and TRAP5b with bone mineral density (BMD) of second metacarpal bone in 103 HD patients and serial changes of these markers just after parathyroidectomy (PTX). Sera NTX and TRAP5b showed a significant positive relationship (R=0.79 P<0.0001). Simple regression analyses showed that both markers were significantly associated with BMD Z-score, whereas 1-84 PTH showed no significant association at all. This result might be attributed to diverse difference among HD patients in skeletal sensitivity to endogenous PTH. In fact, the ratios of TRAP5b/PTH and NTX/PTH denoting PTH sensitivity were significantly higher in postmenopausal female than male patients. Female gender, hemodialysis vintage, and log(PTH) were found to be significant positive determinants of serum log(TRAP5b) by multiple linear regression analysis. Receiver operating curve analysis for young adult mean 70% revealed that sensitivity was more than 95% when the cut-off value was set at 56.5 nmol BCE/L and 340 mU/L, but the specificity was only 29.5% and 34.4% for NTX and TRAP5b, respectively. Multiple regression analysis revealed that both markers were independent determinants of Z-score in two models including respective marker. Serial changes of both markers after PTX in 2 HD patients were comparable with gradual decrease of these markers. However, the reduction was sooner and larger in serum NTX. This sooner reduction might be attributed to the difference in characteristics of these markers regarding the effect of single HD session. Whereas serum NTX decreased, TRAP5b increased significantly after single session. Taken together, both markers give us additional information that cannot be obtained just by using PTH, provided that we know the characteristics of these markers.