Table 2

Summary of quality control studies for total WBC count

Study referenceNumber of SF examples examinedNumber of participating laboratories or observerStatistical resultComment
2530 Heparinised SF3 Laboratories compared with an expert “reference laboratory”Correlation of total counts results of 3 laboratories with those of the reference laboratory. Correlation coefficients from 0.76 to 0.80Only fair In SF from 4 patients, the difference in WBC between laboratories caused the fluids to be erroneously classified as either “non-inflammatory” (WBC <2000/mm3) or “inflammatory”
2530 Heparinised SFReference laboratory only. Intralaboratory study. Two observersCoefficients of variation (CV) for a given sample with total WBC counts >1500/mm3 varied from 1 to 18%. For a given sample with a very low total WBC of < 300/mm3 the CV varied from 20 to 62%Good None of the variations would have clinical significance
24126 LaboratoriesMean total WBC was 6683/mm3 (SD 1992/mm3 (range 2467–12000/mm3)Poor Fairly wide range of cell counts reported