Article Text

other Versions

PDF
Correspondence
Pseudohypercreatininaemia in two patients caused by monoclonal IgM interference with enzymatic assay of creatinine
  1. Tracey Salter1,
  2. James Marsh1,
  3. Bhrigu Sood1,
  4. Callum Livingstone2,
  5. Hugh Gallagher1
  1. 1South West Thames Renal and Transplantation Unit, St Helier Hospital, Carshalton, Surrey, UK
  2. 2Clinical Biochemistry Department, Royal Surrey County Hospital, Guildford, Surrey, UK
  1. Correspondence to Dr Tracey Salter, South West Thames Renal and Transplantation Unit, St Helier Hospital, Wrythe Lane, Carshalton, Surrey SM5 1AA, UK; traceysalter{at}doctors.org.uk

Statistics from Altmetric.com

Introduction

Creatinine is released into the blood following non-enzymatic hydrolysis of creatine in skeletal muscle, and excreted into urine depending on glomerular filtration. The serum creatinine concentration is widely used as a marker of glomerular function because it increases in patients with decreased glomerular filtration rate (GFR). Although GFR is costly to measure, an estimated GFR (eGFR) can be calculated from the serum creatinine concentration. Since 2006, laboratories have calculated eGFR values using the isotope dilution mass spectrometry traceable modification of diet in renal disease equation.1 This standardisation allows direct comparison of creatinine and eGFR results from different laboratories. Reporting of eGFR is a significant advance, but it should be remembered that results are affected by interferences affecting the creatinine assay.

Serum creatinine was initially measured for clinical purposes using alkaline picrate (Jaffé reaction),2 but this method is affected by numerous interferents, including bilirubin, ketones, protein and non-creatinine chromogens.3 Enzymatic assays were later introduced, which are less susceptible to interference3 and more specific being unaffected by non-creatinine chromogens.4 However, interference has been reported from 5-fluorocytosine, ethamsylate, dopamine, dobutamine, nitromethane, creatine, sarcosine and ascorbic acid. Hummel et al5 reported positive interference in enzymatic creatinine measurement caused by monoclonal IgM in three patients with Waldenström's macroglobulinaemia. IgM can precipitate and interfere in the detection step of the reaction. This interference can be avoided by ultrafiltration to remove protein before measuring creatinine. At the time …

View Full Text

Request permissions

If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.