Evaluation of Nucleic Acid Sequence-Based Amplification (NASBA) for Diagnosis and Monitoring of Invasive Aspergillosis : A Preliminary Report

ABSTRACT

OBJECTIVE: In order to improve the diagnosis of invasive aspergillosis (IA) and to establish the monitoring guideline of treatment in neutropenic febrile patients, we evaluated and compared nucleic acid sequence-based amplification (NASBA) with galactomannan-enzyme immunosorbent assay (GM-EIA), and beta-glucan assay. We also determined the tentative cutoff value of NASBA for the presumptive diagnosis of IA. METHODS: Blood samples were collected twice a week from 55 patients with hematologic malignancy during neutropenic fever after chemotherapy or hematopoietic stem cell transplantation. NASBA was carried out by NucliSens kit (BioMerieux) and ECL detector (Sewang Medical, Seoul). GM-EIA was performed by using a sandwich immunocapture ELISA (Platelia Aspergillus, BioRad). beta- glucan was detected using the G test. The tentative cutoff value of NASBA was determined through receiver- operator characteristic (ROC) curve. RESULTS: Total 164 blood samples were tested by three non-culture methods. Based on of EORTC/MSG criteria, 18 out of 55 cases were found to belong to the category of possible to proven cases of IA (1 proven, 2 probable, 15 possible cases). The mean value of NASBA in the IA group was significantly larger than that in the non-IA group (41,665.98 vs 29688.40, respectively, P<0.05). beta- glucan assay showed little concordance to the result of GM-EIA or NASBA. The cutoff value of NASBA determined from ROC curve was 30,000. CONCLUSION: Further study is necessary to determine sensitivity and specificity of NASBA and GM-EIA, and to assess their usefulness for early detection of IA. NASBA cutoff value of 30,000 can be a useful marker for the presumptive diagnosis of IA, and it should be stringently evaluated in the future study.