Hostname: page-component-cd9895bd7-gvvz8 Total loading time: 0 Render date: 2024-12-22T15:08:42.271Z Has data issue: false hasContentIssue false
  • English
  • Français

An international experiment on the Widal-reaction

Published online by Cambridge University Press:  15 May 2009

A. D. Gardner
A. D. Gardner
Affiliation:
From the Medical Research Council's Standards Laboratory, School of Pathology, Oxford
Rights & Permissions [Opens in a new window]

Extract

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

Accuracy of titration may be taken as a measure of the reliability of the methods and work of a laboratory.

With such a small number of titrations as four, a convincing mean, representing the most probable true titre, is hard to calculate. A fairly close approximation, however, is possible in the form of the geometrical mean.

It is also possible to correct for constant local factors which cause the titrations of a given laboratory to run above or below the mean. By all methods of titration a surprisingly large proportion of large errors are recorded.

The most consistent results, with the smallest proportion of large errors, are obtained by the prearranged standard method with a single standardized suspension. The H titres are rather more consistent than the O; probably because H agglutination is easier than O to read correctly.

Local methods give greater differences than the agreed (standard) method. Since the H suspensions used in one laboratory were also sensitive to O agglutination the supposed H titres are unreal, and cannot be treated statistically.

Local O methods give a considerably greater range of error than the standard method, as is shown by a comparison of the mean errors of Tables II and IV, and by the percentages of errors over and under 100 per cent given in Table VI.

The full titres (H or O or both) of the serums measured by local routine Widal methods, with living suspensions in two laboratories and killed ones in the other two, show a considerably greater proportion of large differences than are shown by the titrations with the standard method. They do not, however, differ more widely than the titres obtained with local O suspensions.

The results of the laboratories that use killed H and O suspensions in routine work are more consistent and accurate than those of the laboratories that use living suspensions.

It is suggested that gross technical mistakes are a commoner cause of error than is usually supposed. Errors of dilution of the serums and other technical variations must also be responsible for a part of the very wide range of differences observed.

The use of old strains, tending to roughness, is to be avoided.

Type
Research Article
Information
Journal of Hygiene , Volume 37 , Issue 1 , January 1937 , pp. 124 - 142
Copyright
Copyright © Cambridge University Press 1937

References

page 125 note 1 A. Felix (Lister Institute); A. D. Gardner (Oxford Medical Research Council); H. Schiitze (Lister Institute); W. M. Scott (Ministry of Health Laboratories); P. Bruce White (National Institute of Medical Research). Also consulted, W. W. C. Topley (London School of Hygiene and Tropical Medicine).

page 126 note 1 Ten standard drops=0·4 c.c. If dropped, the serum in each series of 3 tubes should be 10, 5, 2; saline to bring each to 10; suspension 15 drops. The final dilutions are slightly different, viz. 25, 50, 125, 250, 500, 1250. (This note was not included in the circulated directions.)

page 127 note 1 The term “standard method”, used sometimes in this report, implies only that the method ia accepted as the standard method for the purposes of this research.