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

Background: Basophil activation tests (BATs) are useful in identifying culprits of perioperative anaphylaxis (PA), but their 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.

Objective: We sought to investigate whether tryptase levels and clinical parameters may be useful for selecting patients for BATs.

Methods: We performed a 10-year retrospective study in Hong Kong to investigate the performance of BATs associated with tryptase levels (taking during PA) and other clinical parameters.

Results: Of 90 patients, 70 (77.8%) showed significant tryptase level elevation and 37 (41.1%) had a positive BAT result. BAT-positive patients presented with significantly higher absolute levels (15.9 μg/L vs 9.1 μg/L;  = .018), absolute elevation (12.8 μg/L vs 7.1 μg/L;  = .012), and fold elevation (5.6- vs 4.1-fold;  = .014) of acute tryptase than did BAT-negative patients. Among patients with positive BAT result, 94.6% (35 of 37) demonstrated elevated acute tryptase, significantly more than the BAT-negative group (66.0%;  < .001). In regression analysis, tryptase elevation was the sole significant factor correlated to BAT positivity (odds ratio, 10.14; 95% CI, 2.15-47.85;  = .003). Overall, elevated acute tryptase demonstrated a sensitivity of 94.7% and a negative predictive value of 90.0% in predicting positive results with BATs.

Conclusions: We 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 toward selecting labor-intensive and costly tests such as BATs.