Aspergillus specific nested PCR from the site of infection is superior to testing concurrent blood samples in immunocompromised patients with suspected invasive aspergillosis

Abstract

Summary Invasive aspergillosis (IA) is a severe complication in immunocompromised patients. Early diagnosis is crucial to decrease its high mortality, yet the diagnostic gold standard (histopathology and culture) is time‐consuming and cannot offer early confirmation of IA. Detection of IA by polymerase chain reaction (PCR) shows promising potential. Various studies have analysed its diagnostic performance in different clinical settings, especially addressing optimal specimen selection. However, direct comparison of different types of specimens in individual patients though essential, is rarely reported. We systematically assessed the diagnostic performance of an Aspergillus‐specific nested PCR by investigating specimens from the site of infection and comparing it with concurrent blood samples in individual patients (pts) with IA. In a retrospective multicenter analysis PCR was performed on clinical specimens (n = 138) of immunocompromised high‐risk pts (n = 133) from the site of infection together with concurrent blood samples. 38 pts were classified as proven/probable, 67 as possible and 28 as no IA according to 2008 European Organization for Research and Treatment of Cancer/Mycoses Study Group consensus definitions. A considerably superior performance of PCR from the site of infection was observed particularly in pts during antifungal prophylaxis (AFP)/antifungal therapy (AFT). Besides a specificity of 85%, sensitivity varied markedly in BAL (64%), CSF (100%), tissue samples (67%) as opposed to concurrent blood samples (8%). Our results further emphasise the need for investigating clinical samples from the site of infection in case of suspected IA to further establish or rule out the diagnosis.

Clinical Implementation of β-Tubulin Gene-Based Aspergillus Polymerase Chain Reaction for Enhanced Aspergillus Diagnosis in Patients with Hematologic Diseases: A Prospective Observational Study

“…First, the study results were based on the use of only diagnostic-driven Aspergillus PCR through BAL fluid of patients suspected of IPA. We designed this study as a diagnostic-driven test of IPA since samples obtained from the site of infection showed higher sensitivity compared with the blood-based PCR assay due to the high burden of Aspergillus, and routine surveillance might increase the chance of overestimation by colonization [10,17,32,39]. Therefore, the findings of this study should not be extrapolated in the case of blood-based PCR assay or in critically ill patients without underlying hematologic diseases [26,40].…”

Diagnosis of Pneumonia Due to Invasive Molds

“…In patients with suspected IA and pneumonia, specimens from the infection site are more advantageous than specimens collected from blood. In a study that compared diagnostic specimen sensitivities in IA, Aspergillus PCR from BAL showed better sensitivities than when compared with Aspergillus PCR collected from blood (63%) versus (8%), respectively [ 71 ]. The optimal use of Aspergillus PCR is likely to be in combination with Aspergillus antigen detection.…”

Blood Aspergillus PCR: The Good, the Bad, and the Ugly

“…In contrast, BALF GM testing remains reliable independent of neutrophil count, as the lungs are usually the primary site of infections caused by Aspergillus [1,[58][59][60]. Similarly, PCR testing of blood specimens seems to have limited diagnostic ability in non-neutropenic patients, with sensitivities as low as 11% in intensive care unit (ICU) patients [61], while sensitivity and overall diagnostic performance of BALF PCR testing has been shown to be significantly better, reaching sensitivities of 44%-100% [61][62][63][64]. Even in patients with hematological malignancies but without neutropenia, Aspergillus PCR from blood samples proved to be insufficiently sensitive to be diagnostically useful after day 100 post stem cell transplantation [65].…”

“…In fact, Aspergillus PCR from blood specimens is unable to be used to diagnose breakthrough IA, with sensitivities as low as 8% and 0% for probable and proven IA in single blood samples obtained on the day of diagnostic bronchoscopy [62]. One may argue that due to the low fungal burden in early breakthrough infections, the threshold of PCR assays needs to be lowered in order to make detection possible.…”

“…In contrast to blood PCR, Aspergillus PCR from BALF shows reasonable diagnostic performance in patients receiving mold-active prophylaxis. According to recently published studies, the sensitivity of PCR when applied to same-day BALF samples was significantly higher when compared to blood samples reaching 44%-63% in patients on mold-active prophylaxis, with close to perfect specificity [62]. The use of PCR in prophylaxis settings may be restricted to the detection of breakthrough infections and monitoring the response to therapy.…”