Abstract
BackgroundWe assessed the utility of a multi-target, real-time PCR assay for Bordetella pertussis detection and diagnosis in patients with severe respiratory illness (SRI), influenza-like illness (ILI), and asymptomatic controls.MethodsReal-time PCR detection of IS481, pIS1001, hIS1001 and ptxS1 was performed on nasopharyngeal specimens (SRI, ILI and controls) and induced sputum (SRI) collected from June 2012 to May 2016 through respiratory illness surveillance. Using PCR cycle threshold (Ct) value cut-offs, IS481 positive cases were classified as confirmed (Ct < 35) or possible (Ct 35–39) pertussis disease.ResultsAmong 12,922 samples, 146 (1.1%) were IS481 positive of which 62% (90/146) were classified as confirmed. The attributable fraction (AF) was 92.2% (95% CI, 65.6 to 98.2%) and 90.5% (95% CI, 57.5 to 97.9%) amongst SRI and ILI PCR-confirmed pertussis cases, respectively. Amongst possible pertussis cases, AF was 36.9% (95% CI, − 142.3 to 83.6%) and 67.5% (95% CI, − 30.6 to 91.9%) in the SRI and ILI groups, respectively.ConclusionAll IS481 positive specimens could be considered as B. pertussis infection, and potentially pertussis disease with supportive clinical information.
Highlights
We assessed the utility of a multi-target, real-time Polymerase Chain Reaction (PCR) assay for Bordetella pertussis detection and diagnosis in patients with severe respiratory illness (SRI), influenza-like illness (ILI), and asymptomatic controls
We aimed to evaluate a multi-target real-time PCR assay and the use of cycle threshold (Ct) value cut-offs for B. pertussis detection and diagnosis in patients with mild or severe respiratory illness at two sentinel sites in South Africa
PCR detection rate of B. pertussis Overall, B. pertussis was detected in 1.1% (146/12,922, 95% confidence intervals (CI) 1.4 to 1.8) of individuals with detection rates of 1.7% (94/5634, 95% CI 2.0 to 2.8), 1.0% (47/4933, 95% CI 0.9 to 1.5) and 0.2% (5/2355, 95% CI 0.1 to 0.6) in the SRI, ILI and control groups, respectively (SRI vs. ILI p < 0.0001) (Fig. 1)
Summary
We assessed the utility of a multi-target, real-time PCR assay for Bordetella pertussis detection and diagnosis in patients with severe respiratory illness (SRI), influenza-like illness (ILI), and asymptomatic controls. Despite high vaccine coverage with the whole-cell or acellular vaccines and an initial substantial decrease following vaccine introduction, the incidence of pertussis has increased globally during the last two decades [3,4,5,6,7] This has been attributed to increased awareness by clinicians, more sensitive molecular techniques for diagnosis [4, 7], serological markers for identification of infection in adolescents and adults who usually present atypically. Differences in case definitions, may result in reduced sensitivity for detecting pertussis cases using these platforms Different laboratory methods such as bacterial culture, molecular testing and serology may be used to confirm a clinical diagnosis of pertussis, the sensitivity of each method is dependent on the stage of disease and the age of the individual. Culture and molecular testing are recommended for diagnosis during the early
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