Extending the role of tryptase in perioperative anaphylaxis: Predicting positive results in basophil activation tests

Abstract

BackgroundBasophil activation tests (BAT) are useful in identifying culprits of perioperative anaphylaxis (PA), but its utility remains limited due to technical limitations, cost and availability. Being able to prioritize patients with likely higher yields for BAT would be useful in reducing costs and manpower. ObjectiveTo investigate if tryptase levels and clinical parameters may be useful for selecting patients for BAT. MethodsWe performed a ten-year retrospective study in Hong Kong to investigate the performance of BAT associated with tryptase levels (taking during PA) and other clinical parameters. ResultsOut of 90 patients, 70 (77.8%) showed significant tryptase elevation and 37 (41.1%) had positive BAT. BAT-positive patients presented with significantly higher absolute levels (15.9 μg/L vs 9.1 μg/L, p=0.018), absolute elevation (12.8μg/L vs 7.1 μg/L, p=0.012) and fold elevation (5.6- vs 4.1-fold, p=0.014) of acute tryptase; than negative BAT patients. Among patients with positive BAT, 94.6% (35/37) demonstrated elevated acute tryptase, significantly more than the BAT-negative group (66.0%, p<0.001). In regression analysis, tryptase elevation was the sole significant factor correlated to BAT positivity (OR=10.14 [95% CI=2.15-47.85], p=0.003). Overall, elevated acute tryptase demonstrated a sensitivity of 94.7% and a negative predictive value of 90.0% in predicting positive results with BAT. ConclusionWe observed that tryptase elevation is a very sensitive predictor of BAT positivity among patients with identified culprits of PA. Acute elevation of tryptase would not only aid in confirming anaphylaxis, but may also help guide the decision towards selecting labour-intensive and costly in vitro tests such as BAT.