ACP Broadsheet no 125: July 1990. Bacteriological diagnosis of diphtheria.

Diphtheria is no longer diagnosed easily on clinical grounds. The rarity of the disease means that many clinicians never encounter a case, and they may fail to appreciate the clinical importance of a pharyngeal mem- brane, especially if it is thin. Often the first indication of the likelihood of diphtheria is usually given by the laboratory reporting the presence of the causative organism Corynebacterium diphtheriae in routine throat and other swabs taken from the respiratory tract. The mortality in those who have not been immun- ised has changed little, despite the rarity of the disease in Great Britain. The pattern of diphtheria in this country over the past 20 years or so has been of small, sporadic outbreaks often presenting with a fatal case. The ability of the laboratory to make a diagnosis both quickly and reliably, or at least to alert the clinician to the possibility of diphtheria in this situation is therefore of paramount importance.