Traditional and new approaches in detection of invasive aspergillosis

ABSTRACT

The increasing incidence of invasive aspergillosis, this life thereatening infection in immunocompromised patients emphasizes the need to improve the current limited diagnostic tools. Invasive techniques are harmful in these cases so we tried in the present study to establish non invasive diagnostic methods to assist clinicians with the diagnosis of invasive Aspergillosis. We used the two new techniques, the nested PCR technique for detection of Aspergillus DNA in blood and the immunoenzymatic assay [ELISA] for detection of galactomonnan antigen in serum using platelia Aspergillus antigen kit. We evaluated their sensitivity and specificity in relation to culture technique of sputum samples for isolation of Aspergillus. Forty patients with underlying different hematological malignancy and forty control subjects were included in our study. Thirteen cases [32.5] were direct examination positive; four of them [10%] were culture positive while the entire control subjects were negative for both. We found that 13 [32.5] of the patient group were PCR positive and 28 [70%] were ELISA positive while in control group 4 [10%] were PCR positive and 2 [5%] were ELISA positive. The diagnostic performance of Aspergillus galactomannan detection and PCR for Aspergillus in comparison to Aspergillus culture showed high sensitivity of both techniques [100%] while their specificity were [89.3%] and [88.2%] respectively. Although the high sensitivity of both new techniques, the use and interpretation of them are yet of some limited value in the diagnosis of invasive aspergillosis in high risk group because of the high positive results. For a better evaluation of both new techniques in the diagnosis of pulmonary aspergillosis, a long-term study with a larger population sample is necessary with involvement of quantitative PCR assay that may give more knowledge about a particular PCR cut-off values and perhaps permitting better distinction between contamination, colonization and infection