Likelihood ratios and Fagan's nomogram: valuable but underrated tools for in vitro latex sensitization assessment

The relevance of latex allergy has greatly increased in the last decade especially in health workers and in children with spina bifida. Serological testing has been proposed in the diagnosis since history can be inconclusive and skin and provocative testing can induce severe adverse reactions. We evaluated positive likelihood ratios (LRpos) and the Fagan's nomogram in the diagnosis of latex allergy. Thirty patients with positive clinical history, who showed positive results in the skin prick test and in glove-exposure test were compared to 36 blood donors with negative clinical history, who showed negative results in the skin prick test and in glove-exposure test. LRpos was calculated at four different cutoff concentrations of IgE specific to latex measured with a totally automated analyzer. LRs appear better compared to the traditional classes in the reporting of IgE and, coupled with the Fagan's nomogram which allows the calculation of post-test probability, could improve laboratory testing in latex allergy.