July 07, 2017
2 min read

Clinician impressions best way to diagnose Bordetella pertussis

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Individual clinical signs and symptoms are of limited value in diagnosing Bordetella pertussis, and a clinician's overall impression was the most accurate way to determine the likelihood of the infection when a patient first presents, according to a systematic review recently published in The Journal of the American Board of Family Medicine.

However, researchers noted that clinical decisions that combine point-of-care tests, symptoms and signs for the respiratory illness have not yet been developed or validated.

“Ideally, [B. pertussis] treatment should begin within 1 to 2 weeks of the onset of symptoms,” Mark H. Ebell, MD, MS, professor, department of epidemiology, University of Georgia, and colleagues wrote. “However, recognition of patients with [B. pertussis] is challenging, as many of their symptoms overlap with those of viral acute respiratory tract infections, and the recommended diagnostic test, polymerase chain reaction, typically takes several days. Thus, signs and symptoms may be able to help identify patients at high risk for [B. pertussis] for whom testing should be prioritized.”

To see if accurate signs and symptoms of B. pertussis could be determined, researchers used MEDLINE to identify 22 cohort studies of patients with cough or suspected pertussis. These studies’ quality was determined by using QUADAS-2, a tool that assesses the quality of primary diagnostic accuracy studies that should be applied in addition to extracting primary data.

Ebell and colleagues performed a bivariate meta-analysis to calculate summary estimates of accuracy and created summary receiver operating characteristic curves to explore heterogeneity by vaccination status and age. The age of the participants in the analyzed studies ranged from 3 months up to 90 years.

Ebell and colleagues found that the overall clinical impression was the most accurate predictor of B. pertussis (positive likelihood ratio = 3.3; negative likelihood ratio = 0.63). The presence of whooping cough (positive likelihood ratio = 2.1) and posttussive vomiting (positive likelihood ratio = 1.7) somewhat increased the likelihood of B. pertussis, whereas the absence of paroxysmal cough (negative likelihood ratio = 0.58) and the absence of sputum (negative likelihood ratio = 0.63) decreased it. In addition, whooping cough and posttussive vomiting had lower sensitivity in adults. Further, clinical criteria defined by the CDC were sensitive (0.9) but nonspecific. Researchers also noted that typical signs and symptoms of B. pertussis may be more sensitive but less specific in vaccinated patients.

“We have reviewed the best available evidence regarding the clinical diagnosis of [B. pertussis] infection in adults and children. The overall quality of the included studies, aided by the strict inclusion criteria of our systematic review, was good, with over half at low risk of bias. Unfortunately, we must conclude that individual signs and symptoms are of limited value ... The exception is the overall clinical impression,” Ebell and colleagues wrote. “While the overall clinical impression has excellent specificity, it lacks sensitivity and would fail to identify half of the patients with pertussis. However, it clearly suggests that when a clinician has a strong clinical suspicion for pertussis, he or she should trust that suspicion and order confirmatory testing.” - by Janel Miller

Disclosure: The researchers report no relevant financial disclosures.

References: University of Bristol’s Background Document on QUADAS-2