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LETTERS: Doug Jenkinson Whooping cough is quite common and can be diagnosed clinically BMJ 2006; 333: 352 [Full text]

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Whooping cough - clinical diagnosis is unreliable

Ulrich Heininger   (12 August 2006)

Re: Whooping cough - clinical diagnosis is unreliable

Doug Jenkinson   (14 August 2006)

Whooping cough - clinical diagnosis is unreliable 12 August 2006
Ulrich Heininger, Attending physician, paediatric infectious diseases University Children’s Hospital, CH-4005 Basel Send response to journal: Re: Whooping cough - clinical diagnosis is unreliable	Editor Dr. Jenkinson is to be applauded for his continuous clinical work on pertussis (or whooping cough). However, the title and content of his current "letter to the editor" are misleading. The clinical diagnosis of whooping cough is frequently difficult, for the following reasons: - Infections caused by Bordetella pertussis (vaccine preventable) can not be reliably distinguished from those caused by Bordetella parapertussis (not vaccine preventable)(1). - Based on Dr. Jenkinson's clinical definition ("a minimum of three weeks of paroxysmal coughing") only the tip of the iceberg will be diagnosed. B. pertussis infections may be associated with shorter duration and/or lack of paroxysmal coughing. This is mainly true in immunised individuals and adolescents and adults (summarised in 2), but also in unimmunised children (3). - Even if cough with paroxysms (or whooping or posttussive vomiting) is present for 3 weeks or longer, only 57 % of individuals in a vaccine efficacy trial performed by our group had microbiological evidence of Bordetella infection (4). Several other microorganisms can lead to similar symptoms (5). In conclusion, prolonged cough with accompanying symptoms suggestive of pertussis is neither a sensitive nor a specific clinical diagnosis. Specific laboratory tests (PCR, serology) are necessary if a reliable diagnosis of pertussis is to be made. References 1) Heininger U, Stehr K, Schmitt-Grohé S, Lorenz C, Rost R, Christenson P, et al. Clinical characteristics of illness caused by Bordetella parapertussis compared with illness caused by Bordetella pertussis. Pediatr Infect Dis J 1994;13:306-9. 2) Heininger U, Cherry JD. Pertussis immunisation in adolescents and adults--Bordetella pertussis epidemiology should guide vaccination recommendations. Expert Opin Biol Ther 2006;6:685-97. 3) Heininger U, Klich K, Stehr K, Cherry JD. Clinical Findings in Bordetella pertussis Infections: Results of a prospective multicenter surveillance study. Pediatrics 1997; www.pediatrics.org/cgi/content/full/100/6/e10 4) Stehr K, Cherry JD, Heininger U, Schmitt-Grohé S, Überall MA, Laussucq S, et al. A comparative efficacy trial in Germany in infants who received either the Lederle/Takeda acellular pertussis component DTP (DTaP) vaccine, the Lederle whole-cell component DTP vaccine or DT vaccine. Pediatrics 1998;101:1-11. 5) Wirsing von König CH, Rott H, Bogaerts H, Schmitt HJ. A serologic study of organisms possibly associated with pertussis-like coughing. Pediatr Infect Dis J 1998;17:645-9. Competing interests: I have served on advisory boards of several vaccine manufacturers including those who produce pertussis vaccines
Re: Whooping cough - clinical diagnosis is unreliable 14 August 2006
Doug Jenkinson, GP principal Keyworth Health Centre, Bunny Lane, Keyworth, Nottingham NG12 5JU Send response to journal: Re: Re: Whooping cough - clinical diagnosis is unreliable	I welcome Professor Heininger's comments, and I agree that three weeks of paroxysmal coughing is not sufficiently sensitive or specific for a clinical diagnosis. As a clinician I am not too worried about sensitivity as my patients with mild symptoms of B pertussis infection are probably not missing out on useful medical advice. They are, of course, vital for epidemiological modelling. Specificity however, is something I am very concerned about, and I have to admit to having been surprised by the results of testing my clinically diagnosed patients serologically in the last few years. 17 consented to being tested, 15 were positive, one was negative and one was lost. I know these are not big numbers, and the whole cohort was not tested, but it suggests a very high specificity for my clinical diagnosis, and I believe I know the reason why. My clinical diagnosis is based on 3 weeks of paroxysmal coughing. 'Based on' is important. Paroxysmal coughing for this length of time can be caused by many other infections and conditions as Professor Heiningen points out. My observations indicate that B pertussis is the only one likely to cause an EXCLUSIVELY paroxysmal cough for a minimum of 3 weeks. The unique thing about whooping cough is the long intervals of hours between paroxysms when there is not the slightest hint of a cough. Then a paroxysm or series of them occur together, then another perfectly clear interval of usually hours. This is a feature that the patients remember very clearly, although they do not usually put it into words. I believe that most other causes of prolonged paroxysmal coughing do not exhibit this phenomenon. To put it as the paradox that it is, the marker of whooping cough is the absence of coughing (except for paroxysms). A history taking (with as much hindsight as possible) that elucidates this feature will in my view considerably increase specificity. It would be foolish of me to claim it is always as simple as that, because it does not necessarily hold true if there is secondary infection, or excessive sputum production, or in the early stages of the illness. Nevertheless, I am sure it is sufficiently true to make clinical diagnosis a realistic endeavour if this feature is sought. Competing interests: as before