Indexing glomerular filtration rate to body surface area: clinical consequences.

BACKGROUND: Kidney function is mostly expressed in terms of glomerular filtration rate (GFR). A common feature is the expression as ml/min per 1.73 m(2) , which represents the adjustment of the individual kidney function to a standard body surface area (BSA) to allow comparison between individuals. We investigated the impact of indexing GFR to BSA in cancer patients, as this BSA indexation might affect the reported individual kidney function. METHODS: Cross-sectional study of 895 adults who had their kidney function measured with (51) chrome ethylene diamine tetraacetic acid. Mean values of BSA-indexed GFR vs. mean absolute GFR were analyzed with a t-test for paired data. Bland-Altman plot was used to analyze agreement between the indexed and absolute GFR values. RESULTS AND CONCLUSION: BSA-GFR in patients with a BSA <1.60 m(2) overestimated GFR with a bias of 10.08 ml/min (11.46%) and underestimated GFR in those with a BSA >2 m(2) with a bias up to -20.76 ml/min (-23.59%). BSA is not a good normalization index (NI) in patients with extreme body sizes. Therefore, until a better NI is found, we recommend clinicians to use the absolute GFR to calculate individual drug chemotherapy dosage as well as express individual kidney function.

The use of absolute values improves performance of estimation formulae: a retrospective cross sectional study.

BACKGROUND: Estimation of Glomerular Filtration Rate (GFR) by equations such as Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) or Modification of Diet in Renal Disease (MDRD) is usually expressed as a Body Surface Area (BSA) indexed value (ml/min per 1.73 m²). This can have severe clinical consequences in patients with extreme body sizes, resulting in an underestimation in the case of obesity or an overestimation of GFR in the case of underweight patients. The aim of this study was to compare the performance of both estimation formula expressed in ml/min, instead of ml/min per 1.73 m², with a reference method. METHODS: Retrospective single centre cross sectional study of 185 patients. GFR was measured with 51Cr-EDTA and estimated with CKD-EPI and MDRD. Bias, precision and accuracy of absolute estimated GFR was calculated. RESULTS: Bias of CKD-EPI and MDRD formulae expressed as an absolute value was 0.49 and 0.27 ml/min respectively, which is lower than previously reported. Precision was 12.95 and 16.33 and accuracy expressed as P30 was over 92.43% for CKD-EPI. There were no significant differences in GFR between the reference method and the estimation formulae. CONCLUSIONS: The performance of CKD-EPI and MDRD formulae can be significantly improved in the individual patient if the absolute values are used by removing the BSA normalization factor. Absolute estimated GFR by CKD-EPI is comparable to measured GFR, improving the performance of this formula in the assessment of individual kidney function, thus providing clinicians with an alternative to reference methods.

[Hantavirus infection as the cause of haemorrhagic fever with renal syndrome]. / Hantavirus-infektion som årsag til hæmoragisk feber med renalt syndrom.

Hantavirus is an RNA virus that can cause potentially fatal pulmonary and renal diseases in humans. Infections with Hantaviruses occur through inhalation of aerosol from rodent faeces, urine or saliva. The predominant virus type in Denmark is the Puumala virus, which causes the mildest form of haemorrhagic fever with renal syndrome, the so-called nephropathia epidemica (NE) with good prognosis (mortality 0.1-0.4%). The incidence of Hantavirus-infection in Denmark is about ten cases a year. The diagnosis of Hantavirus-infection is based on serology and/or polymerase chain reaction in blood or urine.

[Renal failure in a couple caused by Puumala hantavirus]. / Nyresvigt hos ægtepar forårsaget af Puumala-Hantavirus.

In Scandinavia Puumala hantavirus causes nephropathia epidemica (NE), characterised by an acute debut of fever, headache, increasing back and abdominal pain, thrombocytopenia, increasing azotemia parameters, as well as microscopic haematuria and mild proteinuria. In some cases transitory myopia can be found. The diagnosis is made with a relevant clinical history and serology, and in most cases a kidney biopsy is not necessary. There is a risk of missing cases of NE as in this case, where a couple became infected by Puumala Hantavirus in a high-risk area but became ill in an area with a low prevalence.

Estimation of kidney function in cancer patients.

INTRODUCTION: The Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) formula has not been validated in patients with cancer. The present investigation was undertaken in order to study how well estimated glomerular filtration rate (eGFR) using the new CKD-EPI equation correlates with measured GFR (mGFR) by (51)chrome ethylene diamine tetraacetic acid ((51)Cr-EDTA) clearance in a group of patients with cancer not known as having cancer. MATERIAL AND METHODS: We investigated 185 patients with cancer who were referred for isotope measurement of GFR with (51)Cr-EDTA before initiating chemotherapy treatment. The agreement between CKD-EPI and (51)Cr-EDTA was assessed using a Bland-Altman plot. Test performance was analysed in a contingency table and bias, precision and the percentage of estimates within 30% of the mGFR (P30) were assessed. RESULTS: Bland-Altman plot analysis showed a limit of agreement in the range from -25.59 to 27.92 ml/min./1.73 m(2). This formula was therefore not interchangeable with (51)Cr-EDTA, as the above differences are of clinical importance. Bias was low: 1.16 ml/min./1.73 m(2); P30 was high: 89.73%; and precision was 13.37 ml/min./1.73 m(2). As a screening test, the CKD-EPI had a high specificity of 98% (95% confidence interval (CI): 96 to 100%) and a high negative predictive value 97% (95% CI: 95 to 100%). The accuracy of the validation test was 96% (95% CI: 93 to 99%). CONCLUSION: The CKD-EPI may be used as a screening tool for CKD in the general population, but cannot replace isotope tests when a high GFR measurement accuracy is needed.