PCR in Diagnosis of Invasive Aspergillosis: a Meta-Analysis of Diagnostic Performance

Abstract

Invasive aspergillosis is a difficult-to-diagnose infection with a high mortality rate that affects high-risk groups such as patients with neutropenia and hematologic malignancies. We performed a bivariate meta-analysis of diagnostic data for an Aspergillus sp. PCR assay with blood specimens from high-risk hematology patients. We included all studies involving human subjects that assessed the performance of any PCR assay for invasive aspergillosis in whole blood or serum and that used the European Organization for the treatment of Cancer/Mycoses Study Group criteria as a reference standard. Three investigators independently searched the literature for eligible studies and extracted the data. Out of a total of 37 studies, 25 met strict quality criteria and were included in our evidence synthesis. Twenty-five studies with 2,595 patients were analyzed. The pooled diagnostic performance of whole-blood and serum PCR assays was moderate, with a sensitivity and specificity of 84% (95% confidence interval [CI], 75 to 91%) and 76% (95% CI, 65 to 84%), respectively, suggesting that a positive or negative result is unable, on its own, to confirm or exclude a suspected infection. The performance of a PCR assay of serum was not significantly different from that of whole blood. Notably, at least two positive PCR test results were found to have a specificity of 95% and a sensitivity of 64% for invasive infection, achieving a high positive likelihood ratio of 12.8. Importantly, the European Aspergillus PCR Initiative (EAP-CRI) recommendations improved the performance of the PCR even further when at least two positive specimens were used to define PCR positivity. In conclusion, two positive PCR results should be considered highly indicative of an active Aspergillus sp. infection. Use of the EAPCRI recommendations by clinical laboratories can further enhance PCR performance. D espite advances in treatment and supportive care, invasive aspergillosis (IA) is associated with significant morbidity and mortality rates, especially among patients with hematologic malignancies and hematopoietic stem cell transplant (HSCT) recipients (1, 2). Systemic antifungal prophylaxis is widely used in this patient population (3, 4), and patients with recurrent or persistent fever and prolonged neutropenia frequently require empirical coverage with antifungal agents (5). Timely and accurate diagnosis of an active infection is needed in order to initiate targeted antifungal therapy and avoid unnecessary antifungal treatment, which is often accompanied by a multitude of side effects and the cumulative risk of resistance.There is a need for the development of newer diagnostic techniques that would ideally be able to identify IA rapidly, noninvasively, and at an early stage. To aid in this endeavor, the European Organization for the treatment of Cancer/Mycoses Study Group (EORTC/MSG) developed specific criteria for the diagnosis of IA in 2002 (6), which were later revised in 2008 (7), in an attempt to provide the elusive "gold standard" to which any newe...

Analytical and Clinical Evaluation of the PathoNostics AsperGenius Assay for Detection of Invasive Aspergillosis and Resistance to Azole Antifungal Drugs Directly from Plasma Samples

“…Both sensitivity (80%) and specificity (78%) were comparable to those generated by meta-analytical reviews for testing of blood, where sensitivity ranged from 84 to 88% and specificity ranged from 75 to 76% (11,12). In the previously published evaluations of the AsperGenius assay, the sensitivity and specificity for testing of bronchoalveolar lavage (BAL) fluid were 84% and 91%, respectively, and those for testing of serum were 79% and 91%, respectively (7,8).…”

Analytical and Clinical Evaluation of the PathoNostics AsperGenius Assay for Detection of Invasive Aspergillosis and Resistance to Azole Antifungal Drugs during Testing of Serum Samples

“…With a positivity threshold of 39 cycles, sensitivity and specificity were 78.6% (95% CI, 52.4 to 92.4) and 100% (95% CI, 89.6 to 100), respectively, providing a confident means of diagnosing IA. While the sensitivity was comparable to that for the previous meta-analyses of Aspergillus PCR for testing of blood samples, the specificity was superior, possibly because the meta-analyses included both whole blood and serum/plasma PCR data, whereas this study only utilized serum, previously shown to provide better specificity (16)(17)(18)(19). The sensitivity of the assay is likely to improve through prospective testing, as has been shown for other commercial Aspergillus PCR assays (5,20).…”

Antifungal stewardship considerations for adults and pediatrics

“…69 When used as screening tests for IA in high-risk groups, PCR has demonstrated moderate diagnostic accuracy with sensitivity and specificity ranging between 81%-84% and 76%-79%, respectively. 61,77 In addition, serial positive PCR results are highly indicative of IA, 61,77 and the combination of PCR and BAL GM has been suggested for improved sensitivity without loss of specificity. 78 However, clinical studies are limited by the lack of methodologic standardization and multicenter validation; there are no commercially approved PCR assays to date.…”

“…19,60 In general, results of non-culture-based tests should be interpreted in conjunction with other clinical, radiographic, and microbiologic criteria for IA. 61,62 With respect to serum BDG and GM assays, several meta-analyses have noted heterogeneity of results attributed to differences in study design, patient populations (e.g., hematologic vs other), the criteria used to define a positive test, and the definition of IA. [63][64][65][66][67][68] Among highrisk patients with hematologic malignancies and chemotherapy-induced neutropenia or allogeneic HCT, both tests share a similar sensitivity of 60%-80% and specificity of 90% and higher.…”