Concordance and relevance of total and specific ige allergy laboratory assays at a major jordanian hospital

Abstract

Objective: In vitro allergy diagnostic testing is becoming increasingly common in our area. This study was conducted to correlate and evaluate the concordance between total IgE measurement and specific IgE radioallergosorbent test (RAST) allergy assays. Methods: A total number of 2323 sera samples were received over a five years period (1-1-2007 till 1-1-2012) to perform allergy screen, of which 1627 were analyzed for total IgE only, 969 for RAST only, and 129 for both assays as requested. Total IgE test was performed by enzyme-linked immunosorbent assay (ELISA) and RAST by immunoplot method. Results: A total number of 129 sera samples received for RAST and total IgE testing, were analyzed for both; the results were categorized into 3 groups according to the total IgE level. <20 iu/ml, 20-100 iu/ml, and >100 iu/ml. Of the 47 (36.4%) samples which composed the first group with IgE <20 iu/ml, 2 (1.6%) were positive only for RAST showing the lowest concordance. With no need for performing the RAST test unless the clinical picture was suggestive of allergy and the skin prick test was positive.Of the 30 (23.3%) samples which composed the second group with IgE 20-100 iu/ml, 6 (4.7%) were positive for RAST (Chi-square = 4.8757 and P-value = 0.0272)Of the 52 (40.3%) samples which composed the third group with IgE >100 iu/ml, 19 (14.7%) were significantly positive for RAST compared to the second group (Chi-square 15.3948 and P-value = 0.0001). By the use of regression, RAST positive increased with increasing IgE level (direct proportion) (Pearson Correlation (R) = 0.347, P-value < 0.0001). Conclusion: Total IgE appears to be useful in predicting positive results in allergen specific IgE tests to common allergens. The specific IgEs to certain aero and food allergens showed good correlation with total IgE. Few articles in our area have been published about laboratory testing for allergy, so our findings will enrich the literature database of the area with updated information of the large number of samples being delivered to KHMC, one of the major hospitals in the region. We will not recommend performing the RAST test unless the clinical picture is suggestive of allergy and with a positive skin prick test, for better cost effectiveness, since Jordan is developing country with limited resources.