Broad-Range PCR Coupled with Electrospray Ionization Time of Flight Mass Spectrometry for Detection of Bacteremia and Fungemia in Patients with Neutropenic Fever

Abstract

Infection is an important complication in patients with hematologic malignancies or solid tumors undergoing intensive cytotoxic chemotherapy. In only 20 to 30% of the febrile neutropenic episodes, an infectious agent is detected by conventional cultures. In this prospective study, the performance of broad-range PCR coupled with electrospray ionization time of flight mass spectrometry (PCR/ESI-MS) technology was compared to conventional blood cultures (BC) in a consecutive series of samples from high-risk hematology patients. In 74 patients, BC and a whole-blood sample for PCR/ESI-MS (Iridica BAC BSI; Abbott, Carlsbad, CA, USA) were collected at the start of each febrile neutropenic episode and, in case of persistent fever, also at day 5. During 100 different febrile episodes, 105 blood samples were collected and analyzed by PCR/ESI-MS. There was evidence of a bloodstream infection (BSI) in 36/105 cases (34%), based on 14 cases with both PCR/ESI-MS and BC positivity, 17 cases with BC positivity only, and 5 cases with PCR/ESI-MS positivity only. The sensitivity of PCR/ESI-MS was 45%, specificity was 93%, and the negative predictive value was 80% compared to blood culture. PCR/ESI-MS detected definite pathogens (Fusobacterium nucleatum and Streptococcus pneumoniae) missed by BC, whereas it missed both Gram-negative and Gram-positive organisms detected by BC. PCR/ESI-MS testing detected additional microorganisms but showed a low sensitivity (45%) compared to BC in neutropenic patients. Our results indicate a lower concordance between BC and PCR/ESI-MS in the neutropenic population than what has been previously reported in other patient groups with normal white blood cell distribution, and a lower sensitivity than other PCR-based methods. Infection is a leading cause of mortality in patients with hematologic malignancies or solid tumors, especially in those with prolonged and profound neutropenia (e.g., following remission induction or consolidation therapy for acute leukemia and high-risk myelodysplastic syndrome) and in recipients of myeloablative or reduced-intensity allogeneic stem cell transplantation (and, to a lesser extent, autologous stem cell transplant recipients) (1). Virtually all of these patients present with one or more episodes of fever during the neutropenic phase or during the posttransplant graft-versus-host disease (GvHD) period. Fever during these episodes is usually considered a sign of infection, triggering the immediate administration of broad-spectrum antimicrobial therapy. However, in only 20 to 30% of the febrile neutropenic episodes, an infectious agent is detected by the current gold standard for diagnosing bloodstream infections (BSI) (1, 2). This standard consists of continuous monitoring liquid blood culture (BC), followed by Gram stain, subculturing, identification, and antimicrobial susceptibility testing. However, the suboptimal sensitivity and long turnaround time of blood cultures (range, 2 to 5 days) are major shortcomings. In addition, fever is a highly nonspecific clinical sig...

Emerging Technologies for Molecular Diagnosis of Sepsis

“…We found only one study that investigated polymicrobial specimens. Here, the Iridica platform identified only one causative organism in four out of nine cases of blood culture-positive polymicrobial infection (94).…”

“…Iridica has been evaluated in a limited number of clinical studies across patients with suspected sepsis, systematic inflammatory respiratory syndrome (SIRS), and febrile neutropenia (54,(92)(93)(94)(95). Interestingly, significant differences in sensitivity have been reported across ICU and emergency room (ER) patients (P ϭ 0.005), with higher sensitivity being seen for ICU patients (92).…”

“…Characteristics of studies reviewed for data on the Iridica platform 6 and 8 h with only 30 min of hands-on time for a batch of 6 samples(93,94). However, this technology fails to meet the ideal turnaround time of 1 to 3 h. This technology is not yet approved by the U.S. FDA but is Conformité Européenne (CE) marked, meaning that it complies with the European In-Vitro Diagnostic Devices Directive and is commercially available in Europe(55,91).…”

Diagnosis and Treatment of Candidemia in the Intensive Care Unit

“…20,118 In a meta-analysis of 54 studies, pooled sensitivity and specificity for the diagnosis of IC (mainly candidemia) of PCR methods were 95 and 92%, respectively. 144 However, performance of both in-house and commercial PCR varied markedly across studies, [144][145][146][147][148] and no test has been validated for the diagnosis of candidemia through dedicated, large, multicenter experiences. In view of these considerations, PCR-based tests, although promising, have still to be included in diagnostic guidelines and standardized definitions of candidemia.…”

Performance of PCR/Electrospray Ionization-Mass Spectrometry on Whole Blood for Detection of Bloodstream Microorganisms in Patients with Suspected Sepsis

“…Seven previous studies of PCR/ESI-MS on 5-ml whole-blood samples (9, 10, 14-18) reported BC positivity rates of 5.4 to 34% and PCR/ESI-MS positivity rates of 10.6 to 37% (19). Higher rates of PCR/ESI-MS-positive results (versus BC) were seen in 5 of those studies (9,10,14,16,18), and more BC-positive results (versus PCR/ESI-MS) were seen in 2 studies (15,17). In the largest previous study (n ϭ 616), by Vincent et al (10), BC was positive in 11% and PCR/ESI-MS was positive in 37% of the cases.…”