Vanto et al developed equations for predicting whether an infant with cow's milk allergy is likely to be milk tolerant by 4 years of age. This can help distinguish mild from severe hypersensitivity reactions. The authors are from Turku University Hospital and University of Helsinki in Finland.
The basic premise is that evidence of low level allergy is more likely to be transient, while high level allergy is more likely to persist.
Parameters determined at the time of initial diagnosis of cow milk hypersensitivity:
(1) wheal in the skin prick test with milk antigen
(2) serum concentration of milk-specific IgE
X =
= (-0.3655 * (wheal diameter in mm)) + 2.4469
probability of developing tolerance to cow milk by 4 years of age =
= 1 / (1 + EXP((-1) * X))
Y =
= (-1.9783 * LOG10(milk specific IgE in kU/L)) + 1.6826
where:
• The serum concentration is kU/L = 1,000 U/L. This is important when calculating the LOG10.
probability of developing tolerance to cow milk by 4 years of age =
= 1 / (1 + EXP((-1) * Y))
Rule of Thumb
|
Test
|
Tolerant
|
Intolerant
|
|
skin prick test (SPT)
|
< 5 mm
|
>= 5 mm
|
|
milk-specific IgE
|
< 2 kU/L
|
>= 2 kU/L
|
Performance of rule of thumb:
• The skin prick test correctly identified 83% of those who became tolerant and 71% of those who remained intolerant.
• The serum specific IgE concentration correctly identified 82% of those who became tolerant and 71% of those who remained intolerant.
