Immunotherapy – 2069. Multi-center study on the performance characteristics of two skin test devices - Comforten® and Mult-Test II®

Background

Two multiple test devices, ComforTen (CF10-HollisterStier Allergy) and Multi-Test II (MT-Lincoln Diagnostics), were compared at two allergy clinics. The information generated may assist clinicians in making an informed decision when selecting a skin testing device.

Methods

Subjects at each site (24-AAC/16-NJH) were blind skin-tested on the back with each device in duplicate using a negative control and two histamine positive controls(1 and 6mg/mL). Wheal sizes were recorded (mm) after 10 minutes. After each test, subjects were asked to rate the pain and on two occasions test preference.

Results

Overall, CF10 gave smaller wheals than MT, (combined sites and both histamines1.95 vs. 3.53, p<0.001). Wheals were also smaller at NJH than at AAC (combined devices and histamines 2.33 vs. 3.16, p<0.001). Comparing device- histamine combinations as described by each company’s product insert, i.e. CF10 with 6mg/mL vs. MT with 1mg/mL, wheals were not significantly different (combined centers 4.00 vs. 4.07, p=0.62). The impact of wheal size on sensitivity and specificity to define a positive reaction was examined at 1, 3 and 5mm. Sensitivity increased as the cut-off decreased and trended higher for MT than CF10. Specificity was high (100%) for all cut-off levels at NJH but lower at AAC for MT (80%, 85% and 92%) and CF10 (98%, 98% and 99%). Optimal performance across sites showed that both devices required 6mg/mL histamine but with device specific cut-offs CF10-1mm (sensitivity=93%, specificity=99%), and MT-3mm (sensitivity=94%, specificity=91%). Pain using the two devices appeared to be site-specific. At ACC, there was significantly lower pain using CF10 than there was using MT (0.77 vs. 1.68, p=0.001) while at NJH, there was no significant difference in pain scores. Overall, 57% of subjects showed preference to using CF10, while only 9% preferred MT. The remainder (34%) showed mixed preference.

Conclusions

Both devices produced similar average wheal sizes when used as instructed by the manufacturer with their stated histamine concentration. However optimal results show device specificcut-off criteria usingthe 6mg/mL histamine control. Differences in operator techniques may account for the observation of some inter-site differences which highlights the importance of training.Studies were funded by grants from Jubilant HollisterStier LLC.