The Diphtheria Toxoid-Reaction (Moloney) Test: Its Applications and Significance
Authors: Underwood E. Ashworth 
Published: May 2009

1. The investigation is based on 2666 Moloney tests performed before the injection of prophylactics and 595 tests carried out after the injection of toxoids in prophylactic doses. Methods of reading the test reactions are described.

2. Certain individuals develop sensitivity to toxoid at a very early stage of their existence—even during the first 18 months of life. In the herd the periods of most rapid development of sensitivity to toxoid are between the first and second years, between the fourth and seventh years, and just before the age of fourteen years.

3. For practical purposes the important reactions are those which are designated ++ and +++. Up to the age of 5 years the combined percentages of children who showed these ++ and +++ Moloney reactions did not exceed 3 per cent, at any age. At 7 years the incidence was 9·6 per cent. and thereafter there was a rapid increase until the maximum (43·3 per cent.) was reached at 14 years. Not every individual who shows such ++ or +++ results will develop unpleasant reactions on the injection of toxoids in prophylactic doses. But an investigation into the age and Moloney state of 2041 persons who received prophylactics demonstrated quite definitely that children who showed general and local reactions after inoculation were nearly always over 5 years of age, and most of them (79 per cent.) showed ++ or +++ results with the Moloney test. Hence the test should be used whenever it is intended to inoculate children of school age with prophylactic doses of toxoid or its alum preparations.

4. The assumption that strong positive Moloney reactors are usually immune is unjustified. Of 74 individuals who showed a +++ Moloney reaction 20·3 per cent., and of 173 individuals who showed a ++ Moloney reaction 32·4 per cent, were definitely non-immune as judged by the Schick test. The coefficient of association (Q5) between the two conditions was 0·632.

5. The relationship between positive pseudo-Schick reactions and positive Moloney reactions is examined statistically, and it is shown that the association is not sufficiently high to warrant the substitution of one test for the other. Confirmation of this conclusion was obtained from an examination of the pseudo-Schick and Moloney states of all individuals who showed any degree of local or general reaction after the injection of prophylactic doses of toxoids or other prophylactics.

6. The degree of association between the antitoxic content of the blood serum and the positive Moloney state was investigated in 108 cases. The coefficient (Q5) was found to be in the region of 0·5.

7. The delayed Moloney reaction (+D) is further described and its significance is discussed. The frequency of +D reactions is 1·69±0·17 per cent.

8. In general, a definite Moloney-positive state appears to be permanent. The injection of toxoid in prophylactic doses does not tend to render the injected individual sensitive to toxoid. Exceptions to this rule may be due to the acceleration of a normal process.

9. The incidence of positive Moloney reactions is practically identical in males and in females.

10. The association between the number of children in a family and the number of those who will give positive Moloney reactions is very slight. The effect of an urban environment appears to be more important than the actual family environment in determining the development of sensitivity to toxoid.

11. The relationship between protein skin tests and the Moloney reaction is discussed. Toxoid sensitivity is probably an allergic condition which is due to previous contact with the products of the C. diphtheriae. There is little evidence that age is in itself a factor in the development of sensitivity.