The application of Real-time PCR in invasive aspergillosis diagnosis

Objective To investigate the value of Real-time PCR in the diagnosis of invasive aspergillosis (IA) and to compare it with galactomannan antigen assays. Methods A retrospective study was performed on 110 episodes of hospitalization of 88 patients who were at risk of invasive aspergillosis at Peking University First and Renmin Hospital from May 2008 to December 2010.23 cases with diagnosis and clinical diagnosis IA were classified as infection group and 87 cases with suspected diagnosis and non-IA were classified as non-infeciton group according to the international criterion.Real-time PCR and galactomannan antigen detections were performed on 257 serum samples.A receiver operating characteristic curve (ROC) was developed based on the quantitative cycle numbers and an optimal cut off value of quantification cycle (Cq) was determined.The sensitivity (Se),specificity (Sp),positive predictive value (PPV) and negative predictive value (NPV) were calculated under different considerations among which McNemar chi-square tests were used for statistical analyze. Results The area under ROC curve of Real-time PCR for the diagnosis of IA was 0.91 (95% CI:0.825-0.995) and the optimal cut off value of Cq was 39.45.The Se and Sp of one positive PCR,two positive PCR,one positive GM and two positive GM were 87.0%,79.3%; 58.3%,97.8%; 78.3%,63.2%; and 58.3%,82.6%, respectively. When one positive PCR was considered as the diagnostic criterion of IA, Real-time PCR was able to diagnose 100% and 84.2% of proven and probable IA cases,respectively.The Sp of one/two positive PCR were statistically higher than one/two positive GM (P<0.05),respectively.The Sp of two positive PCR was statistically higher than one positive PCR (P<0.05).The Se and Sp were 65.2%,89.7% and 100%,52.3% for one positive PCR combined one positive GM and one PCR or GM positive,respectively. Conclusions Real-time PCR assays have better sensitivities and specificities than GM in the diagnosis of invasive aspergillosis.When two PCR positive were considered,better specificity and positive predictive value were achieved.(Chin J Lab Med,2013,36:173-177) Key words: Aspergillosis; Real-time polymerase chain reaction; Mannans