Variables affecting the performance of galactomannan assay in high-risk patients at a tertiary care centre in India.

Diagnosis of invasive aspergillosis (IA) in immunocompromised patients using galactomannan ELISA (GM-ELISA) has shown variable sensitivity and specificity. To assess the diagnostic performance of GM-ELISA and analyze the effect of decreasing the cut off value, neutropenia, antifungals and piperacillin-tazobactam (PTZ). Prognostic value using 30 day all-cause mortality was also determined. Serum samples from 81 patients categorized into "proven," "probable," and "possible," categories based on revised EORTC/MSG definitions were tested by GM-ELISA. Sensitivity of GM-ELISA in proven, probable and possible cases was 91.7%, 84.6% and 83.3% respectively. At an index cut-off value of 0.5 an increased sensitivity with minimal loss of specificity was observed. Use of antifungals demonstrated a decrease in sensitivity in proven and possible cases whereas it remained unaffected in probable category. Specificity increased from 75% to 100% with a positivity criterion of >2 consecutive samples. Although an increase in specificity was observed in patients not receiving PTZ, it was not statistically significant. Serial GM index values increased significantly in neutropenic patients and were associated with a poor prognosis. GM-ELISA may be a useful diagnostic and prognostic modality for the detection of IA in high risk patients.