Study on Early Diagnosis of Invasive Aspergillosis in Patients with Hematological Diseases.

Objective To evaluate the value of galactomannan(GM) detection and nest PCR for early diagnosis of invasive aspergillosis (IA) in patients with hematological disease.

Methods GM ELISA and nest PCR was performed to serially screen for circulating galactomannan(GM) and DNA of Aspergillus ssp. Respectively, 96 patients were grouped according to case definitions of the EORTC, including 5 proven IA and 28 probable IA cases. Samples of the patients included serum twice weekly(326) and bronchoalveolar lavage fluid(BALF 12). Sensitivity, specificity and predictive values were calculated respectively and compared.

Results

1. According to the receiver operator characteristic curve(ROC), using a reduced cutoff of 0.5 O.D.I of two-positive GM test result, we can achieved the most optimal results. The sensitivity, specificity, positive predictive value (PPV)and negative predictive value (NPV) of the ELISA test were 85.7%,91.6%,85.7%,91.6%respectively. While for the BALF samples, a increased cutoff 1.0 maybe improve the value of this diagnosis, with sensitivity 50% and specificity 100%.Quantitive results of the serum-based GM antigen can represent the status of IA and were correlated with the prognosis Of IA.Galactomannanemia preceded the development of characteristic findings on CT about 6 days.

2. The nest PCR assay amplifies specifically a region of the 18S rRNA gene that is highly conserved in Aspergillus species and allows detection of down to 5.0 fg/ml of Aspergillus DNA. When two-positive results were used to define an episode as ‘PCR positive’, the sensitivity, specificity, PPV and NPV of the PCR test were 92.9%, 100%,100%,96.0% respectively. For the BALF samples, the sensitivity and specificity decreased to 75%and 60%. The frequency of the consecutively positive results of a patient was correlated with prognosis Of IA. The antifungal therapy usually causes a intermittent positive PCR results. Positve PCR results preceded the development of characteristic findings on CT about 9 days.

Conclusion

1. The cutoff 0.5 of two-positive serum-based GM ELISA test result is the most optimal cutoff value.

2. GM ELISA test is a rapid,reliable method for early diagnosis and treatment of IA, with good sensitivity(85.7%)and specificity(91.6%).

3. GM ELISA test is a good direction for preemptive antifungal therapy in patients with hematological disease at risk.

4. Using two-positive results to define an episode as ‘PCR positive’, great sensitivity(92.9%)and specificity(100%) could be achieved.

5. The serum-based PCR test is useful for screening for Aspergillus spp. in patients with hematological disease at risk but without antifungal treatment.