ImmunoCAP ISAC in food allergy diagnosis: a systematic review of diagnostic test accuracy

The aim of this systematic review is to assess the diagnostic test accuracy of the component-resolved diagnosis device ImmunoCAP ISAC, compared with oral food challenge. Systematic review reported according to the PRISMA-DTA recommendations. Medline, Embase and Cochrane Library databases were searched from inception to May 2019 and updated in March 2021. We included diagnostic test accuracy studies comparing ISAC component results as the index test with oral food challenge as the reference test, in people of any age suspected of IgE-mediated food allergy to milk, egg, peanut, shrimp, hake, apple, peach, kiwi, melon, walnut, hazelnut, wheat or pineapple. Risk of bias was evaluated using the QUADAS-2 tool. We screened 799 titles and included 11 studies - seven prospective and two retrospective cohort studies, two case-control studies. Included studies evaluated IgE to Gald1 (three studies, 300 participants, 140 with egg allergy), Bosd5 (three studies, 242 participants, 146 with milk allergy) and Arah1 or 2 (seven studies, 546 participants, 346 with peanut allergy). No studies were identified for other ISAC components. Risk of bias was high or unclear mainly due to inadequate blinding. Applicability was of high or unclear concern due to unclear thresholds, inappropriate exclusions and variable populations. Gald1 sensitivity ranged from 58 to 84%, specificity 87%-97%. Bosd5 sensitivity 24%-40%, specificity 94%-95%. Arah1 sensitivity 45%-91%, specificity 41%-93%. Arah2 sensitivity 70%-94%, specificity 75%-95%. Diagnostic test accuracy information for ISAC components was only available for milk, egg and peanut. Specificity is generally higher than sensitivity, which contrasts with the performance of skin prick and standard specific IgE tests for diagnosing food allergy. Higher quality information is needed to determine the clinical utility of ISAC for food allergy diagnosis.