Summary of quality control studies for total WBC count
| Study reference | Number of SF examples examined | Number of participating laboratories or observer | Statistical result | Comment |
|---|---|---|---|---|
| 25 | 30 Heparinised SF | 3 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 0.80 | Only 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” |
| 25 | 30 Heparinised SF | Reference laboratory only. Intralaboratory study. Two observers | Coefficients 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 |
| 24 | 1 | 26 Laboratories | Mean total WBC was 6683/mm3 (SD 1992/mm3 (range 2467–12000/mm3) | Poor Fairly wide range of cell counts reported |