External quality assessment of quantitative urinary analysis.

An external quality-assessment scheme was initiated among a group of 13 clinical chemistry laboratories for the urinary analysis of calcium, chloride, creatinine, glucose, osmolality, phosphate, potassium, protein, sodium, urate and urea and also for the estimation of creatinine clearance. The greatest inter-laboratory imprecision occurred in the assay of urinary protein. The results of the survey are compared with similar schemes elsewhere and their significance discussed.