Diagnostic performance of serial serum total tryptase measurement to differentiate positive from negative allergy testing among patients with suspected perioperative hypersensitivity

Background Serum total tryptase has been shown to increase during acute allergic reactions (acute tryptase, T-A); however, few studies have investigated the values of T-A or a combination of T-A and baseline tryptase (T-B) to discriminate positive from negative testing in perioperative hypersensitivity reaction (POH) allergy work-up. The aim of this study was to determine the diagnostic performance of T-A in order to differentiate positive from negative allergy testing suspected POH and analyse the diagnostic performance of serial tryptase levels using several formulas. Methods All patients from the University hospital of Montpellier and Strasbourg, France, who presented with suspected POH and underwent complete drug allergy work-up between March 2011 and December 2019 with available T-A and T-B were included. Four formulas, including a change in T-A > 11 (F1), or >2 + 1.2 x T-B (F2), or >3 + T-B (F3), or >120%T-B (F4), were applied. Results One hundred and sixty-two patients were included, and 131 of them (80.8%) had Grade III or IV reactions. Ninety patients had positive allergy testing. The optimal cut-off value of T-A to distinguish positive from negative allergy testing patients was 9.8 mu g/L with an AUC of 0.817 (95% CI: 0.752-0.882, p < .001). The 93% PPV threshold for T-A was 33 mu g/L (95.8% specificity). Paired tryptase levels according to formulas F2 and F3 yielded the highest Youden index (0.54 and 0.53, respectively). Conclusion The optimal cut-off point for T-A for distinguishing positive from negative allergy testing suspected POH was 9.8 mu g/L. T-A value of 33 mu g/L was required to achieve >90% PPV.