Enzymatic creatine determination as early marker for myocardial infarction diagnosis

Glomerular filtration rate and creatinine production in adult icteric patients

Various methods for serum creatinine determination were compared and validity of the Cockroft-Gault algorithm for calculating creatinine clearance was tested in adult icteric patients. Using conventional Jaffé assays, negative interference is proportional to the serum bilirubin content. Pretreatment of the serum with bilirubin oxidase was more efficient in eliminating bilirubin than pretreatment with potassium ferricyanide. Due to a continued creatine-poor diet and liver dysfunction, erythrocyte creatine levels and creatinine output rate were decreased. Median effect (creatinine equivalent) of non-specific chromogens in the unmodified Jaffé assay was 21 mumol/l (range: 1-108 mumol/l), vs. 19 mumol/l (range: 16-26 mumol/l) for the reference population. In the absence of multi-organ failure, the Cockroft-Gault algorithm could be used for estimating glomerular filtration rate. In patients with multiple organ failure however, we recommend correction for both bilirubin and non-specific chromogens for measuring the serum creatinine concentration.

Enzymatic erythrocyte creatine determinations as an index for cell age

Creatine concentration in red blood cells was determined after ammoniumsulfate precipitation on a clear hemoglobin-free filtrate with a new enzymatic assay making use of bacterial creatinase. The method described is more specific than Griffiths' method and can easily be mechanised and adapted for use in a routine laboratory using classical automated equipment. By contrast with Griffiths' method no significant interferences of amino acids and creatine-like molecules were found. Reference values for this method were 0.379 +/- 0.076 mmol/l. In patients with high turnover of erythrocytes, e.g. haemodialysis patients (0.529 +/- 0.122 mmol/l), and renal insufficiency patients (0.565 +/- 0.145 mmol/l), significantly increased creatine concentration in erythrocytes were observed. Low erythrocyte creatine concentrations were found in chronic ambulatory dialysis patients (0.311 +/- 0.042 mmol/l).