A comparison of attrition rates in patients undergoing sublingual immunotherapy vs subcutaneous immunotherapy.

BACKGROUND: Effective allergy immunotherapy (IT) requires patient compliance. Numerous studies have shown high noncompliance rates in patients undergoing IT. For patients enrolled in subcutaneous IT (SCIT), noncompliance rates were noted to range from 11% to 50%, whereas sublingual IT (SLIT) patients had noncompliance rates ranging from 3% to 25%. Comparing noncompliance rates is difficult because noncompliance in SCIT is defined as withdrawal from therapy, whereas in SLIT it is considered poor adherence to daily administration. The aim of this study was to compare attrition rates in patients enrolled in SCIT vs SLIT, as well as major factors leading to termination of IT.
METHODS: We retrospectively compared attrition rates, IT duration, and reasons for termination between patients enrolled in SCIT (n = 139) and SLIT (n = 78), over a 4-year period.
RESULTS: Attrition rates for SCIT and SLIT were 45% and 41%, respectively (p = 0.669). No significant difference in duration of IT was observed between the groups (≤1 month, p = 0.079; 1-2 months, p = 0.486; 2-3 months, p = 0.165; 3-6 months, p = 0.575; 6-12 months, p = 0.361; 12-24 months, p = 1.000; and ≥24 months, p = 0.258). Among reasons cited for discontinuing IT, SCIT patients reported inconvenience (p = 0.001), whereas SLIT patients indicated efficacy concerns (p = 0.022) as the major basis for withdrawal.
CONCLUSION: No significant difference was observed in attrition rates between SCIT and SLIT. While there was no significant difference in duration of IT prior to withdrawal, there was a trend toward earlier withdrawal in SCIT patients. The reasons for withdrawal, however, were considerably different between the 2 groups.