How do laboratory specialists advise clinicians concerning the use and interpretation of renal tests?

The aim of this study was to elucidate how laboratory specialists advise clinicians concerning renal parameters and to compare their advice with guideline recommendations.

A questionnaire was distributed to laboratory specialists in Norway and The Netherlands together with two case histories from a primary health-care setting and one from a hospital setting, simulating questions from clinicians. The investigations that laboratory specialists suggested were compared to a test panel that was predefined based on clinical practice guideline recommendations (the 'recommended test panel'). The critical differences between two test results (creatinine, estimated glomerular filtration rate [eGFR] and albumin/creatinine ratio [ACR]) and the anticipated precision of the MDRD equation were evaluated.

Fifty-two of the 100 laboratory specialists responded, and most of these were regularly contacted by clinicians to discuss laboratory results. Less than 30% would suggest using the recommended test panel to evaluate renal function in the two primary-care patients. For creatinine and eGFR, median changes stated to signal improvement or deterioration in renal function (creatinine: -14% and +14%, respectively; eGFR: +18% and -13%, respectively) were similar to what could be calculated using information on analytical and within-subject variation from the literature. There were variable critical differences for the ACR results (median values of -50% for improvement and +67% for deterioration). Only 23% of the participants would recommend a gold standard clearance examination for a patient who was to undergo nephrotoxic chemotherapy.

Questions from GPs about renal parameters are answered differently by laboratory specialists, and adherences to guideline recommendations are low on some issues.