Table 1 Performances of Penicillin G zone diameter, nitrocefin disk test, Zone edge test and Penicillin G MIC determination (Vitek 2®) for the detection of penicillinase production in 182 S. epidermidis isolates and comparison of zone edge test results between the 5 investigators
Phenotypic method for penicillinase detection | TP (N) | FP (N) | TN (N) | FN (N) | Total (N) | Se (%) | Sp (%) | PPV (%) | NPV (%) |
|---|---|---|---|---|---|---|---|---|---|
Diameter | 54 | 0 | 127 | 1 | 182 | 98 | 100 | 100 | 99 |
Nitrocefin | 50 | 0 | 127 | 5 | 182 | 91 | 100 | 100 | 96 |
Zone edge test | 54 | 20 | 107 | 1 | 182 | 98 | 84 | 73 | 99 |
MIC | 51 | 1 | 126 | 4 | 182 | 93 | 99 | 98 | 97 |
zone edge test reading/investigators | |||||||||
Investigator 1 | 54 | 21 | 106 | 1 | 182 | 98 | 83 | 72 | 99 |
Investigator 2 | 54 | 19 | 108 | 1 | 182 | 98 | 85 | 74 | 99 |
Investigator 3 | 53 | 43 | 84 | 2 | 182 | 96 | 66 | 55 | 98 |
Investigator 4 | 55 | 28 | 99 | 0 | 182 | 100 | 78 | 66 | 100 |
Investigator 5 | 54 | 5 | 122 | 1 | 182 | 98 | 96 | 93 | 99 |
Final result | 54 | 20 | 107 | 1 | 182 | 98 | 84 | 73 | 99 |