What is the safe FEV1 level on spirometry to start subcutaneous immunotherapy (SCIT) (allergy shots)? At least 80% of predicted.
Dr Ledford explains below:
In the AAAAI’s survey of physician members on immunotherapy- and skin testing–induced fatal reactions and NFRs during the period of 1990-2001, 15 of the 17 fatalities occurred in patients with asthma, and in 9 patients not optimally controlled asthma was considered the susceptibility factor that contributed to the fatal outcome.The most severe NFR, respiratory failure, occurred exclusively in asthmatic patients, and 4 (57%) of 7 asthmatic patients had a baseline FEV1 of less than 70% of predicted value.
In a prospective study of 125 asthmatic patients with mite allergy that used a 3-day rush immunotherapy protocol, FEV1 was identified as a predictor for systemic reactions. In this study 73.3% of the patients with an FEV1 of less than 80% of predicted value experienced an asthma reaction during rush immunotherapy, whereas only 12.6% of patients with an FEV1 of greater than 80% of predicted value had asthmatic reaction.The authors noted that if the patients with an FEV1 of less than 80% of predicted value had been excluded from the study, the systemic reaction rate would have been 19.7% instead of 36%. These studies suggest that labile asthma, severe asthma, or both is a risk factor for immunotherapy.