Prospective comparison of diagnostic tests for bile acid diarrhoea.

BACKGROUND: Bile acid diarrhoea is often missed because gold standard nuclear medicine tauroselcholic [75-Se] acid (SeHCAT) testing has limited availability. Empirical treatment effect has unknown diagnostic performance, whereas plasma 7α-hydroxy-4-cholesten-3-one (C4) is inexpensive but lacks sensitivity. AIMS: To determine diagnostic characteristics of empirical treatment and explore improvements in diagnostics with potential better availability than SeHCAT. METHODS: This diagnostic accuracy study was part of a randomised, placebo-controlled trial of colesevelam. Consecutive patients with chronic diarrhoea attending SeHCAT had blood and stool sampled. Key thresholds were C4 > 46 ng/mL and SeHCAT retention ≤10%. A questionnaire recorded patient-reported empirical treatment effect. We analysed receiver operating characteristics and explored machine learning applied logistic regression and decision tree modelling with internal validation. RESULTS: Ninety-six (38%) of 251 patients had SeHCAT retention ≤10%. The effect of empirical treatment assessed with test results for bile acid studies blinded had 63% (95% confidence interval 44%-79%) sensitivity and 65% (47%-80%) specificity; C4 > 46 ng/mL had 47% (37%-57%) and 92% (87%-96%), respectively. A decision tree combining C4 ≥ 31 ng/mL with ≥1.1 daily watery stools (Bristol type 6 and 7) had 70% (51%-85%) sensitivity and 95% (83%-99%) specificity. The logistic regression model, including C4, the sum of measured stool bile acids and daily watery stools, had 77% (58%-90%) sensitivity and 93% (80%-98%) specificity. CONCLUSIONS: Diagnosis of bile acid diarrhoea using empirical treatment was inadequate. Exploration suggested considerable improvements in the sensitivity of C4-based testing, offering potential widely available diagnostics. Further validation is warranted. CLINICALTRIALS: gov: NCT03876717.

Efficacy and safety of colesevelam for the treatment of bile acid diarrhoea: a double-blind, randomised, placebo-controlled, phase 4 clinical trial.

BACKGROUND: Bile acid diarrhoea is a common but overlooked cause of chronic watery diarrhoea. Plasma 7α-hydroxy-4-cholesten-3-one (C4) is an alternative to the gold standard tauroselcholic [75Se] acid (SeHCAT) test. Low-certainty evidence supports sequestrant treatment, including colesevelam. We aimed to determine the efficacy and safety of colesevelam in bile acid diarrhoea. METHODS: In this randomised, double-blind, placebo-controlled, investigator-initiated phase 4 trial of the sequestrant colesevelam in bile acid diarrhoea (SINBAD), we enrolled consecutive patients aged 18-79 years without inflammatory bowel disease attending SeHCAT testing for suspected bile acid diarrhoea at four Danish secondary care centres. Participants were randomly allocated 1:1 to receive 12 days of treatment with colesevelam (overencapsulated tablets of 625 mg) or placebo, with the starting dose of two capsules twice daily and titrated to effect during the first 5 days of treatment. A pharmacist independent of the clinical investigators generated a randomisation list on the web page randomization.com using block randomisation (randomisation was not stratified). C4 and SeHCAT diagnostic results were blinded during treatment. We treated all patients with diarrhoea, with a daily mean of 3·0 or more bowel movements or 1·0 or more watery bowel movements (Bristol stool scale type 6 and 7). Remission was defined as the absence of both these criteria during treatment days 6-12. The primary outcome was the intention-to-treat remission rate in bile acid diarrhoea diagnosed by C4 concentration greater than 46 ng/mL. A secondary outcome was the intention-to-treat remission rate in bile acid diarrhoea diagnosed by SeHCAT retention of 10% or less. This trial is registered with ClinicalTrials.gov, NCT03876717. FINDINGS: Between Oct 25, 2018, and July 1, 2021, 168 patients were randomly assigned to receive colesevelam (n=84) or placebo (n=84). 41 patients had C4 concentration greater than 46 ng/mL (22 assigned to the colesevelam group and 19 to the placebo group). For the C4-defined primary outcome, 14 (64%) of 22 participants receiving colesevelam versus three (16%) of 19 participants receiving placebo achieved remission (adjusted odds ratio 9·1, 95% CI 1·9-62·8; p=0·011). For the SeHCAT-defined secondary outcome, 75 of the 168 participants had retention of less than 10% (37 assigned to the colesevelam group and 38 assigned to the placebo group); 22 (59%) of 37 participants receiving colesevelam achieved remission versus five (13%) of 38 participants receiving placebo (adjusted odds ratio 11·1, 95% CI 3·4-45·6; p=0·00020). There were no serious adverse events. Common adverse events were transient. For patients receiving colesevelam within the primary outcome population, five had abdominal pain, nine had bloating, and four had nausea. For patients receiving placebo, four had abdominal pain, four had bloating, and one had nausea. No participants with bile acid diarrhoea withdrew due to adverse events. INTERPRETATION: Colesevelam was superior to placebo at inducing remission of bile acid diarrhoea diagnosed with C4 concentration greater than 46 ng/mL. Secondary outcome data suggest similar efficacy treating SeHCAT-defined bile acid diarrhoea. Colesevelam was safe during the treatment. FUNDING: Fabrikant Vilhelm Pedersen og hustrus mindelegat; recommended by the Novo Nordisk Foundation.

Seven Weeks of High-Dose Vitamin D Treatment Reduces the Need for Infliximab Dose-Escalation and Decreases Inflammatory Markers in Crohn's Disease during One-Year Follow-Up.

BACKGROUND: Seven weeks of high-dose vitamin D treatment decreases intestinal IL17A and IFN-γ mRNA expression in active Crohn's disease (CD). In this follow-up study, we investigated whether seven-week vitamin D treatment affected the infliximab response in the following 45 weeks compared to placebo. METHODS: CD patients (n = 40) were initially randomised into four groups: infliximab + vitamin-D; infliximab + placebo-vitamin-D; placebo-infliximab + vitamin-D; and placebo-infliximab + placebo-vitamin-D. Infliximab (5 mg/kg) or placebo-infliximab was administered at weeks 0, 2 and 6. Vitamin D (5 mg bolus followed by 0.5 mg/day for 7 weeks) or placebo-vitamin D was handed out. After the 7-week vitamin D period, all patients received infliximab during follow-up. Results are reported for Group D+ (infliximab + vitamin-D and placebo-infliximab + vitamin-D) and Group D- (infliximab + placebo-vitamin-D and placebo-infliximab + placebo-vitamin-D). RESULTS: Group D- patients had greater needs for infliximab dose escalation during follow-up compared to group D+ (p = 0.05). Group D+ had lower median calprotectin levels week 15 (p = 0.02) and week 23 (p = 0.04) compared to group D-. Throughout follow-up, group D+ had 2.2 times (95% CI: 1.1-4.3) (p = 0.02) lower median CRP levels compared with group D-. CONCLUSIONS: Seven weeks high-dose vitamin D treatment reduces the need for later infliximab dose-escalation and reduces inflammatory markers. EudraCT no. 2013-000971-34.

Decrease in Mucosal IL17A, IFNγ and IL10 Expressions in Active Crohn's Disease Patients Treated with High-Dose Vitamin Alone or Combined with Infliximab.

BACKGROUND: Vitamin D treatment may reduce Crohn's disease (CD) activity by modulating the mucosal immune function. We investigated if high-dose vitamin D +/- infliximab modulated the mucosal cytokine expression in active CD. METHODS: Forty CD patients were randomized into: infliximab + vitamin D; infliximab + placebo-vitamin D; placebo-infliximab + vitamin D or placebo-infliximab + placebo-vitamin D. Infliximab (5 mg/kg) and placebo-infliximab were administered at weeks 0, 2 and 6. Oral vitamin D was administered as bolus 200,000 international units (IU) per week 0 followed by 20,000 IU/day for 7 weeks or placebo. Endoscopy with biopsies was performed at weeks 0 and 7 where endoscopic activity was measured and mucosal mRNA cytokine expression was examined. C-reactive protein (CRP), fecal calprotectin and Harvey-Bradshaw Index (HBI) were measured at weeks 0, 2 and 6. RESULTS: High-dose vitamin D treatment alone and combined with infliximab decreased the IL17A, IFNγ and IL10 expression. High-dose vitamin D alone did not significantly decrease the disease activity, CRP or calprotectin. Combined infliximab and vitamin D treatment was not clinically significantly superior to monotherapy with infliximab. CONCLUSIONS: High-dose vitamin D as monotherapy and combined with infliximab decreases IL17A, IFNγ and IL-10 expression in mucosa within treatment groups. This did not induce a statistically significant decreased disease activity. EudraCT no.2013-000971-34.

Biochemical Diagnosis of Bile Acid Diarrhea: Prospective Comparison With the 75Seleno-Taurohomocholic Acid Test.

INTRODUCTION: The diagnosis of bile acid diarrhea is often missed because the availability of the seleno-taurohomocholic acid (SeHCAT) test is limited. We aimed to compare the biomarkers 7α-hydroxy-4-cholesten-3-one (C4) and fibroblast growth factor 19 (FGF19) with the SeHCAT test. METHODS: Patients with chronic diarrhea without intestinal resection referred for SeHCAT were prospectively recruited for this diagnostic accuracy study. Blood was sampled at fasting and after a stimulation meal with chenodeoxycholic acid. SeHCAT retention ≤10% defined bile acid diarrhea and >10% defined miscellaneous diarrhea. Receiver operating characteristics (ROC) were analyzed with SeHCAT as the gold standard. www.clinicaltrials.gov (NCT03059537). RESULTS: Patients with bile acid diarrhea (n = 26) had mean C4 of 30 ng/mL (95% confidence interval: 19-46) vs 8 (7-11; P < 0.001) in the miscellaneous diarrhea group (n = 45). Area under the ROC curve (ROCAUC) for C4 was 0.83 (0.72-0.93). C4 < 15 ng/mL had 85% (74%-96%) negative predictive value; C4 > 48 ng/mL had 82% (59%-100%) positive predictive value. Twenty patients had C4 values 15-48 ng/mL, of whom 11/20 had SeHCAT ≤10%. Median fasting FGF19 was 72 pg/mL (interquartile range: 53-146) vs 119 (84-240) (P = 0.004); ROCAUC was 0.71 (0.58-0.83). Stimulated FGF19 responses did not differ (P = 0.54). DISCUSSION: We identified C4 thresholds with clinically useful predictive values for the diagnosis of and screening for bile acid diarrhea in patients with chronic watery diarrhea. Further validation of the cutoff values with the placebo-controlled effect of sequestrant therapy is warranted (see Visual Abstract, Supplementary Digital Content 2, http://links.lww.com/AJG/B603).

Fecal Microbiota Transplantation Is Superior to Fidaxomicin for Treatment of Recurrent Clostridium difficile Infection.

BACKGROUND & AIMS: Fecal microbiota transplantation (FMT) is recommended for treatment of recurrent Clostridium difficile infection (rCDI). We performed a single-center randomized trial to compare the effects of FMT with those of fidaxomicin and vancomycin. METHODS: We studied consecutive adults with rCDI seen at a gastroenterology clinic in Denmark from April 5, 2016 through June 10, 2018. Patients were randomly assigned to a group that received FMT, applied by colonoscopy or nasojejunal tube, after 4-10 days of vancomycin (125 mg 4 times daily; FMTv; n = 24), 10 days of fidaxomicin (200 mg twice daily; n = 24), or 10 days of vancomycin (125 mg 4 times daily; n = 16). Patients who had rCDI after this course of treatment and patients who could not be randomly assigned to groups were offered rescue FMTv. The primary outcome was combined clinical resolution and a negative result from a polymerase chain reaction test for Clostridium difficile (CD) toxin 8 weeks after the allocated treatment. Secondary end points included clinical resolution at week 8. RESULTS: All 64 patients received their assigned treatment. The combination of clinical resolution and negative results from the test for CD were observed in 17 patients given FMTv (71%), 8 patients given fidaxomicin (33%), and 3 patients given vancomycin (19%; P = .009 for FMTv vs fidaxomicin; P = .001 for FMTv vs vancomycin; P = .31 for fidaxomicin vs vancomycin). Clinical resolution was observed in 22 patients given FMTv (92%), 10 patients given fidaxomicin (42%), and 3 patients given vancomycin (19%; P = .0002; P < .0001; P = .13). Results did not differ significantly between patients who received FMTv as their initial therapy and patients who received rescue FMTv. There was 1 serious adverse event that might have been related to FMTv. CONCLUSIONS: In a randomized trial of patients with rCDI, we found the FMTv combination superior to fidaxomicin or vancomycin based on end points of clinical and microbiological resolution or clinical resolution alone. ClinicalTrials.gov, number NCT02743234; EudraCT, j.no 2015-003004-24.

Obeticholic acid for severe bile acid diarrhea with intestinal failure: A case report and review of the literature.

Bile acid diarrhea results from excessive amounts of bile acids entering the colon due to hepatic overexcretion of bile acids or bile acid malabsorption in the terminal ileum. The main therapies include bile acid sequestrants, such as colestyramine and colesevelam, which may be given in combination with the opioid receptor agonist loperamide. Some patients are refractory to conventional treatments. We report the use of the farnesoid X receptor agonist obeticholic acid in a patient with refractory bile acid diarrhea and subsequent intestinal failure. A 32-year-old woman with quiescent colonic Crohn's disease and a normal terminal ileum had been diagnosed with severe bile acid malabsorption and complained of watery diarrhea and fatigue. The diarrhea resulted in hypokalemia and sodium depletion that made her dependent on twice weekly intravenous fluid and electrolyte infusions. Conventional therapies with colestyramine, colesevelam, and loperamide had no effect. Second-line antisecretory therapies with pantoprazole, liraglutide, and octreotide also failed. Third-line treatment with obeticholic acid reduced the number of stools from an average of 13 to an average of 7 per 24 h and improved the patient's quality of life. The fluid and electrolyte balances normalized. The effect was sustained during follow-up for 6 mo with treatment at a daily dosage of 25 mg. The diarrhea worsened shortly after cessation of obeticholic acid. This case report supports the initial report that obeticholic acid may reduce bile acid production and improve symptoms in patients with bile acid diarrhea.

Diagnosis and treatment of unexplained anemia with iron deficiency without overt bleeding.

A general overview is given of the causes of anemia with iron deficiency as well as the pathogenesis of anemia and the para-clinical diagnosis of anemia. Anemia with iron deficiency but without overt GI bleeding is associated with a risk of malignant disease of the gastrointestinal tract; upper gastrointestinal cancer is 1/7 as common as colon cancer. Benign gastrointestinal causes of anemia are iron malabsorption (atrophic gastritis, celiac disease, chronic inflammation, and bariatric surgery) and chronic blood loss due to gastrointestinal ulcerations. The following diagnostic strategy is recommended for unexplained anemia with iron deficiency: conduct serological celiac disease screening with transglutaminase antibody (IgA type) and IgA testing and perform bidirectional endoscopy (gastroscopy and colonoscopy). Bidirectional endoscopy is not required in premenopausal women < 40 years of age. Small intestine investigation (capsule endoscopy, CT, or MRI enterography) is not recommended routinely after negative bidirectional endoscopy but should be conducted if there are red flags indicating malignant or inflammatory small bowel disease (e.g., involuntary weight loss, abdominal pain or increased CRP). Targeted treatment of any cause of anemia with iron deficiency found on diagnostic assessment should be initiated. In addition, iron supplementation should be administered, with the goal of normalizing hemoglobin levels and replenishing iron stores. Oral treatment with a 100-200 mg daily dose of elemental iron is recommended (lower dose if side effects), but 3-6 months of oral iron therapy is often required to achieve therapeutic goals. Intravenous iron therapy is used if oral treatment lacks efficacy or causes side effects or in the presence of intestinal malabsorption or prolonged inflammation. Three algorithms are given for the following conditions: a) the paraclinical diagnosis of anemia with iron deficiency; b) the diagnostic work-up for unexplained anemia with iron deficiency without overt bleeding; and c) how to proceed after negative bidirectional endoscopy of the gastrointestinal tract.

Active Crohn's disease is associated with low vitamin D levels.

BACKGROUND AND AIMS: Crohn's disease prevalence increases with increasing latitude. Because most vitamin D comes from sunlight exposure and murine models of intestinal inflammation have demonstrated beneficial effects of 1,25-(OH)2 vitamin D treatment, we hypothesised that Crohn's disease activity is associated with low vitamin D levels. METHODS: In a cross-sectional study of 182 CD patients and 62 healthy controls, we measured serum 25-OH vitamin D. Stratified analysis was used to compare 25-OH vitamin D levels with Crohn's disease activity index, C-reactive protein, smoking status, intake of oral vitamin D supplements and seasonal variation in CD patients and healthy controls. RESULTS: Serum 25-OH vitamin D was inversely associated with disease activity: Median 25-OH vitamin D levels of Crohn's disease in remission, mildly, and moderately active diseases evaluated by Crohn's disease activity index were 64, 49, and 21 nmol/l (p<0.01) and by CRP 68, 76, and 35 nmol/l (p<0.05), respectively. Patients who took oral vitamin D supplementation had lower Crohn's disease activity index (p<0.05) and C-reactive protein (p=0.07) than non-users. Crohn's disease patients who smoked had lower vitamin D levels (51 nmol/l) than patients who did not smoke (76 nmol/l), p<0.01. Overall, Crohn's disease patients did not differ from healthy controls regarding 25-OH vitamin D levels. CONCLUSIONS: Active Crohn's disease was associated with low serum 25-OH vitamin D. Patients who smoked had lower 25-OH vitamin D levels than patients who did not smoke, independently of disease activity.

Vitamin D deficiency in cirrhosis relates to liver dysfunction rather than aetiology.

AIM: To examine the vitamin D status in patients with alcoholic cirrhosis compared to those with primary biliary cirrhosis. METHODS: Our retrospective case series comprised 89 patients with alcoholic cirrhosis and 34 patients with primary biliary cirrhosis who visited our outpatient clinic in 2005 and underwent a serum vitamin D status assessment. RESULTS: Among the patients with alcoholic cirrhosis, 85% had serum vitamin D levels below 50 nmol/L and 55% had levels below 25 nmol/L, as compared to 60% and 16% of the patients with primary biliary cirrhosis, respectively (P < 0.001). In both groups, serum vitamin D levels decreased with increasing liver disease severity, as determined by the Child-Pugh score. CONCLUSION: Vitamin D deficiency in cirrhosis relates to liver dysfunction rather than aetiology, with lower levels of vitamin D in alcoholic cirrhosis than in primary biliary cirrhosis.

A 15-year-old girl with severe hemolytic Wilson's crisis recovered without transplantation after extracorporeal circulation with the Prometheus system.

BACKGROUND: Wilson's disease (WD) can present in a fulminant form with hepatocellular dysfunction, hemolysis and multiorgan failure (Wilson's crisis). We present a previously healthy young woman with severe WD whose WD severity score was 13. A score >11 indicates a poor chance of survival and liver transplantation will usually be recommended. METHODS: Penicillamine and acetylcysteine were initially administered, but the patient deteriorated further, and extracorporeal liver support with the Prometheus FPSA (fractionated plasma separation and adsorption) system was initiated. The patient was treated 6 h daily during 3 consecutive days. RESULTS: Severe hemolysis was reduced to low-grade hemolysis, with no further need for transfusions. The mental state improved and after 4 months practically all biochemical markers were normalized. CONCLUSIONS: This is the first report of FPSA albumin dialysis of a patient with Wilson's crisis and the first report in which a patient with a WD score >11 survived without transplantation.

1,25-dihydroxyvitamin D3 and dexamethasone increase interleukin-10 production in CD4+ T cells from patients with Crohn's disease.

BACKGROUND AND AIM: In Crohn's disease (CD), epidemiological data and animal studies suggest that vitamin D (vitD) has protective immune-modulating properties. 1,25-dihydroxyvitamin D3 and dexamethasone (DEX) induce interleukin (IL)-10 productions in healthy controls (HC) T cells. We studied if 1,25-dihydroxyvitamin D3 with and without DEX could induce IL-10 production, downregulate pro-inflammatory Interferon (IFN)-gamma and Tumor Necrosis Factor (TNF)-alpha production, and influence cell kinetics in peripheral CD4+ T cells from CD patients. METHODS: CD4+ T cells were separated from peripheral blood from CD patients and HC. Cells were activated by anti-CD3 and anti-CD28 in the presence of 1,25-dihydroxyvitamin D3 and/or DEX. Cytokine levels, proliferation, and apoptosis were measured following 7 days of culture. RESULTS: In T cells from CD patients, 1,25-dihydroxyvitamin D3 and DEX increased IL-10 production from a median of 0.08 ng/ml to 0.2 ng/ml (p<0.01) and downregulated IFN-gamma production from 8.3 ng/ml to 3.1 ng/ml (p<0.01). The induced IL-10 increase in cultures from HC (0.2 ng/ml to 1.0 ng/ml, p<0.01) was significantly higher than in CD patients (p<0.05). In CD cultures, the IL-4 production increased from 0.3 ng/ml to 0.5 ng/ml (p<0.01) and IL-6 production from 2.5 ng/ml to 6.1 ng/ml (p<0.05). Similar changes in cytokine levels were observed with 1,25-dihydroxyvitamin D3 independently of DEX. In addition, 1,25-dihydroxyvitamin D3 and DEX decreased proliferation and reduced viability of T cells. CONCLUSION: We found that 1,25-dihydroxyvitamin D3 with and without DEX stimulation increased IL-10 and reduced IFN-gamma production. These findings suggest that vitD may play a therapeutic role in CD.

[Vitamin D insufficiency--possible etiologic factor of autoimmune diseases]. / D-vitamin-insufficiens--en mulig aetiologisk faktor ved autoimmune sygdomme.

The primary source of vitamin D in humans is sun exposure to the skin. The incidence of certain autoimmune diseases correlates positively with latitude. As vitamin D production increases with sun exposure, vitamin D insufficiency is hypothesised to influence the development of autoimmune diseases. In experimental animal and cellular studies in vitro 1.25-(OH)2-vitamin D reduces inflammation. This article discusses the role of vitamin D in inflammatory bowel disease, type 1 diabetes mellitus, multiple sclerosis, and rheumatoid arthritis.

Glycosaminoglycans increase levels of free and bioactive IGF-I in vitro.

BACKGROUND: It is unclear how IGFs become separated from their IGF-binding proteins (IGFBPs) in vivo. However, the IGFBPs possess binding sites for glycosaminoglycans (GAGs) and interaction with GAGs alters IGFBP ligand affinity. Accordingly, GAGs may control IGF bioavailability. To test this hypothesis, we investigated the effect of GAGs on serum levels of free and bioactive IGF-I, total IGF-I, and IGFBPs in vitro. METHODS: Serum was incubated with increasing concentrations of six different GAGs (heparin, tinzaparin (Innohep), dermatan sulfate, heparan sulfate, non-anticoagulant (nac) heparin, and nac low-molecular weight heparin). To investigate for reversibility, heparin was co-incubated with protamine sulfate (PS). Finally, the effect of heparin was studied in serum from pregnant and post partum women, normal subjects and patients with type 1 diabetes. RESULTS: All GAGs increased free IGF-I in a dose-dependent manner (P<0.0001), whereas total IGF-I and IGFBP levels remained unchanged. However, the potency of the GAGs differed significantly (P<0.0001) and did not relate to their anti-coagulating activity. The effect of heparin on free IGF-I was fully reversed by PS. Heparin increased free and bioactive IGF-I in all tested sera (P<0.0001), but the increase was most pronounced in samples from pregnant women (P<0.0001). CONCLUSION: All tested GAGs stimulated the release of free and bioactive IGF-I in several types of serum, most likely by reversible interaction with the IGFBPs. The effect was most pronounced in pregnancy sera, which are characterized by extensive IGFBP-3 proteolysis. Our findings support the view that GAGs localized in the vessel wall and attached to the extracellular matrix control IGF-I tissue accessibility and bioactivity.

Development and clinical evaluation of a novel immunoassay for the binary complex of IGF-I and IGF-binding protein-1 in human serum.

Correlation studies have suggested that IGF-binding protein (IGFBP)-1 is a dynamic regulator of free IGF-I. To further study this, we developed a monoclonal immunofluorometric assay specific for the binary complex of IGF-I and IGFBP-1 in human serum. An IGFBP-1 antibody, which recognizes all phospho-forms of IGFBP-1, was used for coating. An europium-labeled IGF-I antibody served as tracer. Assay incubation was performed at conditions approaching those in vivo (i.e. pH 7.4, 37 C). The assay was highly specific: no signal was obtained unless both IGF-I and IGFBP-1 were present and neither IGFBP-2, -3, -4, nor IGF-II caused any cross-reaction. The linear standard curve covered 3 orders of magnitude, and within and in-between assay coefficients of variation were less than 5 and 15%, respectively. To study the dynamic relationship between free IGF-I and binary complex formation, seven healthy subjects were fasted for 72 h. Samples were collected every 3 h. During fasting, free IGF-I was reduced by two thirds (P < 0.0001). IGFBP-1 and the binary complex increased in parallel (P < 0.0001), and levels correlated positively in all subjects (0.89 < or = r < or = 0.98; P < 0.0001). Free IGF-I correlated inversely with IGFBP-1 (-0.81 < or = r < or = -0.48; 0.0001 < or = P < or = 0.05) and the binary complex (-0.79 < or = r < or = -0.41; 0.0001 < or = P < or = 0.05). To study overnight fasting levels, we compared healthy controls and patients with type 1 diabetes and chronic renal failure (n = 10), because these patients show profound alterations in their IGF-system. In both groups, the binary complex was increased about 2.5-fold (P < 0.0001), whereas IGFBP-1 was increased by 5- to 6-fold (P < 0.0001). Accordingly, free IGF-I was severely reduced (P < 0.0001). In conclusion, the assay enables us to study the role of IGFBP-1 as a dynamic regulator of free IGF-I. Our results clearly show that IGFBP-1 and free IGF-I are tightly associated peptides. Furthermore, it has now become possible to compare levels of IGF-I carried within the binary complex IGFBP-1:IGF-I in different (patho-) physiological conditions.