7 was accepted (Table 3). When the cut-off was lowered to 0.5, four episodes had negative results on consecutive samples. On the other hand, 20 episodes out of 33 with no IA had positive GM results with a cut-off of 0.7 (Table 4). Four more episodes were rendered false positive when the cut-off was lowered to 0.5. Characteristics of patients with Anti-infection Compound Library in vivo false positive GM results and factors coinciding with the period of false positivities were summarised in Table 4. Patients received beta lactam antibiotics in all episodes but one. Piperacillin-tazobactam and/or amoxicillin-clavulanate were used in 19 episodes out of 58. In particular cases with false positive
results, piperacillin-tazobactam was used in four of 20 episodes and amoxicillin in one episode (Table 4). With regard to different cut-off values (1.5, 1.0, 0.7 and 0.5), calculations were made to define the sensitivity, specificity, negative and positive predictive values (Tables 5 and 6). In recent years, monitoring of serum GM levels by ELISA has become popular for the early diagnosis of IA because of its standardisation and the applicability in routine practice. In this study, we evaluated the way we handle high-risk patients for IA and the applicability BVD-523 of serum GM measurements in our routine practice and surveillance. The reported sensitivity and
the specificity of the serum GM measurements by Aspergillus Platelia® kit vary widely in the literature, mostly because of heterogeneity among the studies.20 Sensitivities as high as 100% are reported, whereas some studies report no positive results in proven cases or sensitivity as low as 17%.14,16,28–31 A recent meta-analysis revealed an overall sensitivity of 61% and specificity of 93% for proven and probable cases.20 Although the sensitivity
of GM assay differs among patient groups and may be very low, its specificity is quite good.20 This variation in the performance of the test is thought to be related to the inconsistency of the patient populations and the specimens used, the uncontrolled variables during the specimen transport or processing, Carbohydrate and the different disease definitions and cut-off points.25 In this study, with only five episodes of IA (proven and probable), we found 60% sensitivity and a very low specificity (20.8%) for GM assay with the use of the generally accepted 0.5 cut-off value. The very low positive predictive values in our study can also be explained by the low number of IA in our patient population. The predictive values of a test in clinical practice depend critically on the prevalence of the abnormality in the patients being tested; the rarer the abnormality the lower will be the positive predictive value. Several factors may explain the very low sensitivity.