Table 4

Quality control studies for MSUM

Study referenceNumber of SF samples examinedNumbers of participating laboratories or observersResultsComment
2511 SF of which 7 contained MSUM crystals2 Laboratories compared with reference laboratory5/7 MSUM crystal SF were correctly identified by 1 laboratoryFair
3/7 MSUM crystal SF were correctly identified by 1 laboratory
There was one false positive result
Sensitivity was calculated as 62.5%
244 SF of which 1contained MSUM alone, and 1 contained both MSUM and CPPD25 Laboratories39/50 MSUM crystal SF correctly identified, 78% AccuracyGood
2712 SF of which 4 contained MSUM6 Laboratories19/24 MSUM crystal SF correctly identified, 15/16 by 4 laboratories (good)4 Laboratories good
But the results for the other 2 laboratories were poor (50% correct and scored 2 false negatives and 3 false positives)2 Laboratories poor
264 SF of which 1 contained MSUM25 Laboratories19/25 Laboratories identified MSUM crystal SF correctly. 24% False positivesGood
2896 slide preparations of SF, 41 with synthetic MSUM added. Concentrations of MSUM 0.1–100 μg/ml1 LaboratoryMean sensitivity 69%MSUM identification improved at higher crystal concentrations
6 ObserversMean specificity 93%
2911 samples, 3 with MSUM Gram stained and wet preparation set up for each sample1 Laboratory78% SensitivityResults equally good for Gram stained and wet preparations of SF
3 Observers100% Specificity