Table 3

Summary of quality control studies for differential WBC count

Study referenceNumber of SF samples examinedNumber of participating laboratories or observersStatistical resultComments
2524 Heparinised SF3 Laboratories compared with an expert “reference laboratory”Comparing the 3 “test” laboratories with the reference laboratory. In one or more of the test laboratories, the %PMN cells in 12/24 SF samples fell outside (2SD) of the 95% confidence limits of the value determined by the reference laboratory (Correlation coefficients for %PMN cell findings in 3 laboratories compared with the reference laboratory were 0.73, 0.84, 0.94. respectively)Variable Occasional wide variation in results and misidentification of cells
2524 Heparinised SFReference laboratory only Intralaboratory study 2 ObserversThe mean %PMN cells counted by 2 observers were similar—maximum difference of 25%. When a 2 sided significance test for difference from previous value was applied, 23/24 percentages were within 95% confidence intervalGood
24126 Hospital laboratoriesThe percentage of PMN cells identified varied from 0 to 30%, mean 13.8 (SD 8.6) (median 11%)Considerable variation