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Clinical evaluation of commercial nucleic acid amplification tests in patients with suspected sepsis.

ABSTRACT: Sepsis is a serious medical condition requiring timely administered, appropriate antibiotic therapy. Blood culture is regarded as the gold standard for aetiological diagnosis of sepsis, but it suffers from low sensitivity and long turnaround time. Thus, nucleic acid amplification tests (NAATs) have emerged to shorten the time to identification of causative microbes. The aim of the present study was to evaluate the clinical utility in everyday practice in the emergency department of two commercial NAATs in patients suspected with sepsis.During a six-week period, blood samples were collected consecutively from all adult patients admitted to the general emergency department for suspicion of a community-onset sepsis and treated with intravenous antibiotics. Along with conventional blood cultures, multiplex PCR (Magicplex™) was performed on whole blood specimens whereas portions from blood culture bottles were used for analysis by microarray-based assay (Prove-it™). The aetiological significance of identified organisms was determined by two infectious disease physicians based on clinical presentation and expected pathogenicity.Among 382 episodes of suspected sepsis, clinically relevant microbes were detected by blood culture in 42 episodes (11%), by multiplex PCR in 37 episodes (9.7%), and by microarray in 32 episodes (8.4%). Although moderate agreement with blood culture (kappa 0.50), the multiplex PCR added diagnostic value by timely detection of 15 clinically relevant findings in blood culture-negative specimens. Results of the microarray corresponded very well to those of blood culture (kappa 0.90), but were available just marginally prior to blood culture results.The use of NAATs on whole blood specimens in adjunct to current culture-based methods provides a clinical add-on value by allowing for detection of organisms missed by blood culture. However, the aetiological significance of findings detected by NAATs should be interpreted with caution as the high analytical sensitivity may add findings that do not necessarily corroborate with the clinical diagnosis.

SUBMITTER: Ljungstrom L

PROVIDER: S-EPMC4419503 | biostudies-literature | 2015

REPOSITORIES: biostudies-literature

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Clinical evaluation of commercial nucleic acid amplification tests in patients with suspected sepsis.

Ljungström Lars L Enroth Helena H Claesson Berndt E B BE Ovemyr Ida I Karlsson Jesper J Fröberg Berit B Brodin Anna-Karin AK Pernestig Anna-Karin AK Jacobsson Gunnar G Andersson Rune R Karlsson Diana D

BMC infectious diseases 20150428

<h4>Background</h4>Sepsis is a serious medical condition requiring timely administered, appropriate antibiotic therapy. Blood culture is regarded as the gold standard for aetiological diagnosis of sepsis, but it suffers from low sensitivity and long turnaround time. Thus, nucleic acid amplification tests (NAATs) have emerged to shorten the time to identification of causative microbes. The aim of the present study was to evaluate the clinical utility in everyday practice in the emergency departme ...[more]

PMID: 25928122

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Project description:Battling infection is a major healthcare objective. Untreated infections can rapidly evolve toward the condition of sepsis in which the body begins to fail and resuscitation becomes critical and tenuous. Identification of infection followed by rapid antimicrobial treatment are primary goals of medical care, but precise identification of offending organisms by current methods is slow and broad spectrum empirical therapy is employed to cover most potential pathogens. Current methods for identification of bacterial pathogens in a clinical setting typically require days of time, or a 4- to 8-h growth phase followed by DNA extraction, purification and PCR-based amplification. We demonstrate rapid (70-120 min) genetic diagnostics methods utilizing loop-mediated isothermal amplification (LAMP) to test for 15 common infection pathogen targets, called the Infection Diagnosis Panel (In-Dx). The method utilizes filtration to rapidly concentrate bacteria in sample matrices with lower bacterial loads and direct LAMP amplification without DNA purification from clinical blood, urine, wound, sputum and stool samples. The In-Dx panel was tested using two methods of detection: (1) real-time thermocycler fluorescent detection of LAMP amplification and (2) visual discrimination of color change in the presence of Eriochrome Black T (EBT) dye following amplification. In total, 239 duplicate samples were collected (31 blood, 122 urine, 73 mucocutaneous wound/swab, 11 sputum and two stool) from 229 prospectively enrolled hospital patients with suspected clinical infection and analyzed both at the hospital and by In-Dx. Sensitivity (Se) of the In-Dx panel targets pathogens from urine samples by In-Dx was 91.1% and specificity (Sp) was 97.3%, with a positive predictive value (PPV) of 53.7% and a negative predictive value (NPV) of 99.7% as compared to clinical microbial detection methods. Sensitivity of detection of the In-Dx panel from mucocutaneous swab samples was 65.5% with a Sp of 99.3%, and a PPV of 84% and NPV of 98% as compared to clinical microbial detection methods. Results indicate the LAMP-based In-Dx panel allows rapid and precise diagnosis of clinical infections by targeted pathogens across multiple culture types for point-of-care utilization.

Project description:The Magicplex Sepsis Real-time Test (MST) is a commercial multiplex PCR that can detect more than 90 different pathogens in blood, with an analysis time of six hours. The aim of the present study was to evaluate this method for the detection of bloodstream infection (BSI). An EDTA whole blood sample for MST was collected together with blood cultures (BC) from patients with suspected sepsis at the Emergency Department of a university hospital. Among 696 study patients, 322 (46%) patients were positive with at least one method; 128 (18%) were BC positive and 268 (38%) were MST positive. Considering BC to be the gold standard, MST had an overall sensitivity of 47%, specificity of 66%, positive predictive value (PPV) of 23%, and a negative predictive value of 87%. Among the MST positive samples with a negative BC, coagulase-negative staphylococci (CoNS) and species that rarely cause community-acquired BSI were frequently noted. However, the quantification cycle (Cq) values of the MST+/BC- results were often high. We thus hypothesized that the performance of the MST test could be improved if the Cq cut-off level was adjusted downwards. With a lower Cq cut-off value, i.e. 6.0 for Staphylococcus species and 9.0 for all other species, the number of MST positive cases decreased to 83 (12%) and the overall sensitivity decreased to 38%. However, the PPV increased to 59% and the specificity increased to 96%, as many MST positive results for CoNS and bacteria that rarely cause community-acquired BSI turned MST negative. In conclusion, our study shows that with a lower Cq cut-off value, the MST will detect less contaminants and findings with unclear relevance, but to the cost of a lower sensitivity. Consequently, we consider that a positive MST results with a Cq value above the adjusted cut-off should be interpreted with caution, as the result might be clinically irrelevant. In a correspondent way, quantitative results could probably be useful in the interpretation of positive results from other molecular assays for the detection of BSI.

Dataset Information

Clinical evaluation of commercial nucleic acid amplification tests in patients with suspected sepsis.

Publications

Clinical evaluation of commercial nucleic acid amplification tests in patients with suspected sepsis.

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