Molecular Assay for Aspergillosis Evaluated Under Clinical Conditions

A molecular test to detect the presence of invasive Aspergillus (IA) in critical care and hematology patients has been evaluated.

The polymerase chain reaction (PCR) assay was appraised to test the reliability and performance of the Myconostica assay compared with clinical diagnosis and conventional diagnostic tests, such as culture and blood tests.

A single-center prospective study was carried out at the Università Cattolica del Sacro Cuore (Rome, Italy) on a total of 158 bronchoalveolar lavage (BAL) fluid specimens that were consecutively collected from 68 hematology and 90 intensive care unit patients. There were 16 of 17 (94.1%) specimens from patients with proven/probable IA were that were positive with the commercial PCR MycAssay (Myconostica; Manchester, UK) and 15 of these 16 patients were also positive by an “in house” PCR assay. Of 141 specimens from patients without proven/probable IA, 139 (98.6%) were MycAssay negative. Fifteen of 16 (94.1%) positive patients were also positive for BAL galactomannan (GM) at an index cutoff of ≥1.0 (index range, 1.1 to 8.3), as were three patients without IA but with pulmonary fusariosis.

Interestingly, in seven of the PCR-positive BAL specimens that tested culture positive for Aspergillus species cycle-threshold values were earlier than those of specimens with a culture-negative result. In conclusion, the MycAssay Aspergillus as reported by Lab21, (Cambridge, UK) appears to be a sensitive and specific molecular test for the diagnosis of IA, and its performance is comparable to that of the GM assay. However, more large studies are necessary to establish its clinical utility in high-risk settings.

Aspergillus is an airborne fungus that can infect immunosuppressed patients, for example, those undergoing organ transplantation or treatment for hematological malignancies IA also poses a risk to hospitalized patients, such as those suffering with chronic obstructive pulmonary disease (COPD), liver cirrhosis and those taking corticosteroid treatment. There are estimated to be over 200,000 IA cases annually worldwide and over 10 million patients at risk. Mortality rates vary by patient group ranging from 30% to 85%.

Berwyn Clarke, PhD, chief scientific officer at Lab21 said: “The results of this evaluation confirm that our new CE-marked assay for the diagnosis of IA represents a first-in-class addition to fungal diagnostics enabling faster, more reliable and sensitive case detection. We are in the process of conducting additional studies to firmly establish its clinical utility in high-risk settings.” The study was published on October 19, 2011, in the Journal of Clinical Microbiology.

Related Links:
Università Cattolica del Sacro Cuore
Myconostica
Lab21