Systemic reactions to inhalant immunotherapy using 1:1 target dosing

The 2007 immunotherapy practice parameters advocate maintenance dosing at 1:1 (1:20 maintenance concentrate). There is limited literature exploring the effect of 1:1 dosing on the rate of systemic reactions to subcutaneous immunotherapy (SRITs).

To investigate the effects of 1:1 dosing on SRITs in a large, academic practice.

We conducted a retrospective cohort study of all nonvenom and noncluster SRITs that occurred between 2005 and 2011. SRITs that occurred from August 2008 through December 2011, postparameter dosing (post-PD) was initiated, were compared to SRITs that occurred from January 2005 to July 2008 with preparameter dosing (pre-PD) using 1:50 as a maintenance concentrate.

A total of 269 SRITs occurred in a 7-year period. Significantly more post-PD SRITs (131 of 38,548 injections) occurred than pre-PD SRITs (132 of 52,833 injections) (0.34% vs 0.25%, P = .01). However, when excluding 44 SRITs that occurred in established pre-PD patients transitioned to post-PD, there was no significant difference in SRIT rate (0.25% vs 0.22%), World Allergy Organization (WAO) grade, or SRIT time to onset. Nonred (non-1:1) vials accounted for a significantly larger proportion of all post-PD SRITs compared with all pre-PD SRITs (50.7% vs 31.1%, adjusted P = .009). Prior SRITs were reported less frequently among persons with post-PD SRITs (29.2% vs 70.8%, adjusted P = .009). In an adjusted logistic regression model, male sex (odds ratio, 7.9; 95% CI, 2.4-26) and longer time to reaction onset (odds ratio, 0.94; 95% CI, 0.89-0.99) were associated with higher WAO severity grade reactions.

Pre-PD vs post-PD SRIT rates were not significantly different, adjusting for patients transitioned from established pre-PD to post-PD. This finding suggests that post-PD is as safe as pre-PD. Male sex and faster time to reaction onset were associated with higher WAO grade reactions.