Skin prick test in milk allergic patients undergoing oral immunotherapy: Does the milk form used for skin tests matter?

Abstract

SPT is the most commonly used confirmatory test for an IgE-mediated milk allergy. However, food SPTs are not standardized. We aimed to assess the accuracy of SPTs with extract, diluted, and undiluted milk to detect desensitization in children with milk allergy undergoing OIT. Children with milk allergy undergoing OIT and controls were recruited from Montreal Children's Hospital (MCH), British Columbia Children's Hospital (BCCH) and The Hospital for Sick Children (SickKids). Participants in the active arm received a weekly increase in milk until 200 ml of pure milk was tolerated. SPT using milk extract (Omega), diluted 2% milk (1:10), and undiluted milk was done at the study entry and when 200 ml of pure milk was reached. Participants in the control arm had SPT at study entry and 12 months later before they entered the active arm. Among 53 children who reached 200 ml, the median age was 12 years and 54.7% were males. The mean decrease in wheal size at 200 ml from the baseline was 3.78 mm (95%CI, 2.55-5.01), 5.05 mm (95% CI, 3.68-6.41), and 5.05 mm (95% CI, 3.29-6.80) for milk extract, diluted and undiluted milk respectively. Among 32 controls, the median age was 10 years and 62.5% were males. There was no significant change in wheal diameter over a one-year period regardless of the skin test method. Response to extract behaved similarly to whole food (Diluted and undiluted) and thus can be used to follow sensitization in the context of a desensitization program.

Keywords: Desensitization; allergy; diluted milk; extract; milk; oral immunotherapy (OIT); skin prick test (SPT).

Figure 1

Total of 93 participants were recruited for this study, 8 children were excluded (7 passed the entry challenge and 1 lost to follow-up shortly after the challenge). The remaining 85 children were randomized to either OIT (n = 48) or control (n = 37). Among the 48 children in the OIT group, 16 were withdrawn and 31 children reached 200 ml of pure milk. Among the 37 controls, 28 children crossed over to OIT after one year of observation, 5 LTF and the remaining 4 are still in the observation period. Out of the 28 who crossed over to OIT, 22 children reached 200 ml. *LTF, Lost to follow; OIT, Oral Immunotherapy.