Value of Real-Time PCR for the Early Detection of Invasive Fungal Infection in Immunodeficient Children

Abstract

SUMMARY T he incidence of IFI has increased dramatically among immunocompromised children in the past two decades. A number of well-established risk factors associated with the development of IFI is frequently found in this population including, intensive immunosuppressive chemotherapy, increasing awareness of these infections, and the widespread use of broad-spectrum antibiotics and central venous catheters (Sheevani et al., 2013). The present study aimed to evaluate the role of real-time PCR, using a Panfungal marker, as a rapid test for early diagnosis of invasive fungal infection in immunocompromised patients. The study included 50 immunocompromised children, 20 females and 30 males, suspected of having invasive fungal infection. Venous blood was withdrawn from them and was subjected to conventional blood culture and real-time PCR assay for the panfungal marker. Positive blood cultures were further subcultured on SDA for the identification of the growing fungus. The results of this study revealed that twenty patients (20/50, 40%) had positive blood cultures whereas thirty patients (30/50, 60%) had negative cultures. Candida spp. was the most commonly isolated organism being isolated from 15 out of the 20 (75%) positive blood cultures Whereas, Aspergillus spp. was isolated from 4 out of the 20 (20%) positive cultures and Penicillium spp. was isolated from the remaining case (1/20, 5%). The real-time PCR assay for the detection of the panfungal marker showed that out of the 50 studied cases, 32 (64%) were positive whereas 18 cases (36%) had negative results. There was a statistically moderate agreement between the results of blood culture and that of real-time PCR for the detection of the panfungal marker (Kappa = 0.545). The twenty cases that were positive by the blood cultures were also positive by the Panfungal assay. Yet, 12 out of 30 (40%) blood culture negative cases were found to be positive by the panfungal PCR assay and the remaining 18 cases (60%) were negative by both tests. The diagnostic performance of blood culture was calculated, considering the PCR as the gold standard. The sensitivity of the routine blood culture was found to be 62.5%, the specificity was 100%, PPV was 100% and the NPV was 60% whereas the PCR for the detection of panfungal marker was found to have 100% sensitivity, 60% specificity, PPV of 62.5% and NPV of 100% as compared to the blood culture. There was no statistically significant difference between the PCR-positive and the PCR-negative cases regarding age, disease duration, neutrophil count, duration of neutropenia, CRP levels, duration of fever, number of antibiotics taken and the duration of antibiotics intake (P>0.05). There was no statistically significant association between gender and PCR results. Also, no association was found between the intake of antifungal drugs and PCR results. In addition, no association was found between patients’ outcome and PCR results. There was a highly significant association between EORTIC-classification and the results of panfungal PCR.