Agglutination tests in the diagnosis of enteric fever in the inoculated

Abstract

1. Early blood culture is the best method of laboratory diagnosis in the inoculated case of enteric fever, but agglutination tests may give useful information.2. In inoculated cases of enteric fever O and Vi agglutinins may be absent or present only at low titres. Steadily rising titres are not the rule and the titres more often fluctuate.3. Complete agglutination at titres over 1: 80 for TO, over 1: 40 for AO, or over 1: 10 for Vi is suggestive but not diagnostic of an active infection.4. Non-specific stimulation of the O and Vi agglutinins in the inoculated affects mainly the lower range of titres which are probably of little diagnostic significance.5. Previous inoculations increase the proportion of people with residual O agglutinins within 6 months of the last inoculation but do not affect the Vi agglutinins.6. Vi agglutinins may be present in normal inoculated persons who are not carriers.

The diagnostic value of the widal test in the inoculated

“…In 35 control sera, 12 normal (W.R.) specimens and 23 from cases of definitely diagnosed non-enteric febrile illnesses, T ' O' titres of 1:400 were found four times and of 1:200 another six times. Wilson (1945), also working in India and using a similar technique, obtained higher figures for healthy inoculated men than most other workers. The recurrent annual inoculation of the subjects examined by Wilson and by the author may be a partial explanation of their findings.…”

“…On this there is very little published evidence, and the data mentioned above are too meagre for consideration. Wilson (1945) found a T 'O' titre of 1:320 or over in 1-6 % of patients with diseases other than enteric as. compared with 0-5% of healthy inoculated individuals.…”

“…The technique described by Wilson (1945) was employed except that the serum dilutions were prepared with graduated pipettes, not by the method of doubling dilutions. Standard agglutinable cultures were provided by the Central Military Pathological Laboratory, Poona.…”

“…1 suggest that a significant rise occurs only in about a quarter of the cases, less often than a fall. Wilson (1945) also found that 'no variation in titre during the disease can be taken as diagnostic for enteric fever', although 'rising or fluctuating titres appear more frequently in enteric fever than in other diseases'. The lack of value of the Widal test in the diagnosis of enteric fever in Service personnel, i.e.…”

Questions and Comments

“…Although a rise in serum titre was not found in every case, the results indicated that chloramphenicol does not interfere markedly with agglutinin production. Wilson (1945) and Mole (1948) investigated the agglutinin titre in the serum of inoculated persons with enteric fever who had not been treated with chloramphenicol. Their results were very variable; steadily rising titres were not the rule.…”