French experience of quality assessment of quantitative urinary analysis

Since 1986, clinical biochemists from the Rhône alpes area, in collaboration with a non-profit-making association (Pro Bio Qual), have been conducting an inter-laboratory quality assurance program for quantitative urine analysis. We investigated the precision and accuracy of individual methods and measurement systems routinely used in the monthly control for 13 analytes: albumin, alpha-amylase, calcium, chloride, creatinine, glucose, magnesium, phosphorus, potassium, total protein, sodium, urea, and urate. The number of laboratories participating in the program increased from 60 in 1986 to 277 in 1999. In 1986, the greatest inter-laboratory imprecision occurred in the assay of urinary total protein, because the commonly used sulfosalicylic acid turbidimetric methods displayed poor precision. Since 1989, the increasing use of pyrogallol red or Coomasie Blue dye colorimetric methods has improved inter-laboratory precision markedly. The acceptable precision and good practicability have encouraged the general use of the pyrogallol red method. As for albumin analysis, which uses a specific immunologic method, the precision was reasonably good. Quality assessment of chloride and sodium decreased when the method performance improved for other analytes (calcium, creatinine, glucose, magnesium, phosphorus, potassium, urea, urate). This program has helped the laboratories to improve the quality of quantitative urine analysis, particularly for total protein.