CRD summary

The authors concluded that the limited evidence suggested that posttussive emesis or inspiratory whoop symptoms moderately changed the likelihood of pertussis diagnosis in a non-outbreak setting. Given the potential for bias in the review, the uncertain study quality, and the inclusion of only a small number of studies with small sample sizes, the authors' conclusions should be interpreted with caution.

Authors' objectives

To assess the diagnostic value of three classic symptoms for diagnosing pertussis (Bordetella pertussis) infection in adolescents and adults in non-outbreak settings.

Searching

MEDLINE (from 1966) and EMBASE (from 1969) were searched up to April 2010 for relevant English language articles. Search terms were reported. In addition, reference lists of retrieved articles were manually searched.

Study selection

Studies that assessed the value of paroxysmal cough, posttussive emesis and inspiratory whoop in diagnosing pertussis in children (older than five years), adolescents and adults with cough illness, in non-outbreak and non-active surveillance settings, were eligible for inclusion. Eligible studies were required to include confirmed diagnosis of pertussis using a reference standard (polymerase chain reaction (PCR) testing or pertussis toxin serological testing, with or without culture, or clinical diagnosis based on definite clinical exposure) and contain extractable data. Studies diagnosing patients using serological testing were only eligible if they used sensitivity and specificity to measure anti-pertussis toxin antibodies.

Included studies were conducted in South Korea, the UK and the USA, and included outpatients with acute to severe cough. The median age of patients in each study was nine, 30 and 35 years (range five to 83 years); the median cough duration at presentation was 15 and 36 days (range four to 80 days), where reported.

Two reviewers independently screened relevant studies for inclusion.

Assessment of study quality

The authors stated that studies were assessed for relevant biases (e.g. verification and selection bias), but no other details were provided.

Data extraction

Two reviewers independently extracted data and disagreements were resolved by discussion or referral to a third reviewer, if necessary.

Methods of synthesis

A random-effects model was used to combine sensitivity, specificity, and positive and negative likelihood ratios (LRs) by type of symptom. Statistical heterogeneity was assessed using the I² statistic. Separate analysis was undertaken on the study including only children and adolescents (aged 5 to 16).

Results of the review

Three studies (n=486 participants; range 102 to 212) were included in the review. One study used non-consecutive enrolment and included a small percentage of eligible patients; verification bias was evident in one study.

The presence of posttussive emesis and inspiratory whoop symptoms moderately increased the likelihood of pertussis (posttussive emesis, positive LR 1.8, 95% CI 1.4 to 2.2; inspiratory whoop,1.9 positive LR, 95% CI 1.4 to 2.6). The presence of paroxysmal cough also increased the likelihood of pertussis, but this was only slightly greater than 1 (positive LR 1.1, 95% CI 1.1 to 1.2). The absence of paroxysmal cough and posttussive emesis reduced the likelihood of pertussis (paroxysmal cough, negative LR 0.52, 95% CI 0.27 to 1.0; posttussive emesis, negative LR 0.58, 95% CI 0.44 to 0.77). The absence of inspiratory whoop also reduced the likelihood of pertussis (negative LR 0.78, 95% CI 0.66 to 0.93). There was no evidence of statistical heterogeneity.

Separate analysis of the study including only children and adolescents showed similar pooled likelihood ratios.

Pooled sensitivities and specificities were also reported in the review.

Authors' conclusions

The limited evidence suggested that posttussive emesis or inspiratory whoop moderately changed the likelihood of the diagnosis of pertussis in a non-outbreak setting.

CRD commentary

The review question was clear and was supported by appropriate inclusion criteria for patients, intervention and outcome. The literature search was restricted to published articles written in English, which meant that language bias may have been introduced and potentially relevant studies may have been missed. The authors undertook study selection and data extraction in duplicate, but as the process was unclear for validity assessment, reviewer error and bias could not be ruled out.

The authors stated that they assessed for study biases but, as few details were provided, it was difficult to determine the quality of the studies. The authors reported clinical and methodological heterogeneity among studies, which meant that it may not have been appropriate to combine the results, but there was no evidence of statistical heterogeneity.

Given the potential for bias in the review, the uncertain study quality, and the inclusion of only a small number of studies with small sample sizes, the authors' conclusions should be interpreted with caution.

Implications of the review for practice and research

Practice: The authors stated that clinicians must use their overall clinical impression to decide whether additional testing or empirical treatment is needed. They also suggested that the findings do no apply to patients with a cough illness in outbreak setting where the pre-test probability of pertussis may be substantially higher, but the thresholds to test and empirically treat for pertussis may be lower.

Research: The authors stated that research is needed to investigate the combination of a whooping cough and posttussive emesis in the diagnosis of pertussis.

Funding

Not reported.

Bibliographic details

Cornia PB, Hersh AL, Lipsky BA, Newman TB, Gonzales R. Does this coughing adolescent or adult patient have pertussis? JAMA 2010; 304(8): 890-896. [PubMed: 20736473]

Original Paper URL

http://jama.ama-assn.org/cgi/content/abstract/304/8/890

Indexing Status

Subject indexing assigned by NLM

MeSH

Adolescent; Adult; Aged; Bordetella pertussis /genetics /immunology /isolation & purification /pathogenicity; Cough /etiology; Diagnosis, Differential; Humans; Middle Aged; Pertussis Vaccine /immunology; United States /epidemiology; Vomiting /etiology; Whooping Cough /complications /diagnosis /epidemiology /immunology

AccessionNumber

12010005892

Database entry date

15/09/2010

Record Status

This is a critical abstract of a systematic review that meets the criteria for inclusion on DARE. Each critical abstract contains a brief summary of the review methods, results and conclusions followed by a detailed critical assessment on the reliability of the review and the conclusions drawn.