Published online by Cambridge University Press: 15 May 2009
The literature dealing with the intradermal test in whooping cough has been reviewed, and the claims as to the specific value of the test have been investigated in 1300 cases.
A method for the extraction of endotoxin from Haemophilus pertussis has been described and the intradermal response to this preparation compared with that following whole vaccine.
The findings in this investigation do not support the claim that the intradermal response to Sauer's vaccine in the strength commonly employed (10,000 million organisms per c.c.) is of value either in demonstrating immunity to whooping cough or in the early diagnosis of this disease. The bacterial content of this vaccine appears to be too high for skin-testing purposes, giving rise to inflammatory lesions of a non-specific character rather than to allergic reactions of specific value. These reactions are less apparent when the vaccine is employed in a diluted form.
The intradermal response to pertussis endotoxin, on the other hand, though not invariably consisting of a clear-cut reaction (and in this respect falling short of the ideal as a reagent) is more consistent with the development of the allergic state towards H. pertussis, reactions presumably of this nature being present in the skin of approximately 85% of children with a past history of whooping cough. Similar reactions, however, can be elicited in the skin of about 30% of individuals with no history of the disease; but in view of the fact that, unlike the more invasive virus diseases, many individuals never develop whooping cough in spite of almost certain exposure when young, it is suggested that latent immunization or recent contact with the causative organism might account for this phenomenon. Whether these reactions indicate merely sensitization or a definite immunity to pertussis must remain, for the time being, sub judice.
The onset of bacterial hypersensitiveness, as judged by the pertussis endotoxin test, appears about the 10th day of whooping cough and becomes heightened during the subsequent course of the disease. Ultimately this cutaneous allergy undergoes a regression, which, however, is not always complete. For this reason the pertussis endotoxin test would appear to be of some value in assessing the immune state of the individual, and also as a diagnostic reaction in early, atypical or late cases of whooping cough where bacteriological findings by the cough plate method have proved disappointing.