Multi-Test® PC

Abstract

Background: Percutaneous allergen skin testing remains an established benchmark for diagnosing atopic disease. The reliability of skin testing depends greatly on the performance of allergen extracts used, methods used, and the presence of antihistamine medications.

Objective: To determine the differential effect of cetirizine on 2 different concentrations of histamine control solution and 5 common allergens used for percutaneous skin testing.

Methods: Twelve individuals underwent skin testing with histamine (1 and 6 mg/mL), control diluent, and 5 common aeroallergens. Wheal and flare measurements were measured in a masked fashion by a single operator. Cetirizine was administered for 4 consecutive days to determine the effect on both histamine and allergen wheal and flare responses.

Results: A total of 384 skin tests were performed on 12 volunteers. Cetirizine began to suppress wheal and flare responses at 1 hour (P < .05), with maximum suppression at day 5 (P < .05). Wheal and flare responses returned to greater than 90% baseline within 4 days of not taking cetirizine. Suppression was more apparent with 1 vs 6 mg/mL of histamine (62% vs 33%). Four of the 12 individuals taking cetirizine had a positive skin test result using 6 mg/mL of histamine control when the 1-mg/mL histamine test result was negative. Importantly, twice as many individuals had false-negative allergen responses using 6 mg/mL of histamine vs the 1 mg/mL as a positive control, although this finding did not reach statistical significance.

Conclusion: The use of a 6-mg/mL histamine control for some percutaneous skin test devices may result in more false-negative allergen responses because of the inability to detect the presence of antihistamines.

BACKGROUND: Allergen skin prick testing remains an essential tool for diagnosing atopic disease and guiding
treatment. Sensitivity needs to be defined for newly introduced devices.
OBJECTIVE: Our aim was to compare the performance of 10 current allergy skin prick test devices. 
METHODS: Single- and multiheaded skin test devices (n [ 10) were applied by a single operator in a prospective randomized manner. Histamine (1 and 6 mg/mL) and control diluent were introduced at 6 randomized locations onto the upper and lower arms of healthy subjects. Wheal and flare reactions were measured independently by 2 masked technicians.
RESULTS: Twenty-four subjects provided consent, and 768 skin tests were placed. Mean wheal diameter among devices differed from 3.0 mm (ComforTen; Hollister-Stier, Spokane, Wash) to 6.8 mm (UniTest PC; Lincoln Diagnostics, Decatur, Ill) using 1 mg/mL histamine (P < .001) and 4.8 mm (GREER Pick; Greer, Lenoir, NC) to 8.4 mm (Duotip-Test II; Lincoln Diagnostics, Decatur, Ill; and Sharp-Test; Panatrex, Placentia, Calif) using 6 mg/mL histamine (P < .001). The false-negative rates ranged from 0% to 45% with 1 mg/mL histamine. The analytical specificity was 100% for all devices tested. All devices were well tolerated, with average pain score of less than 4 on a 10-point visual analog scale. Pain scores were higher among women, but this did not reach statistical significance. The Multi-Test PC and the UniTest PC had the lowest pain scores compared with the other devices.
CONCLUSIONS: All 10 skin prick test devices displayed good analytical sensitivity and specificity; however, 3 mm cannot arbitrarily be used as a positive threshold. The use of histamine at 1 mg/mL is unacceptable for certain devices but may be preferable for the most sensitive devices. On average, there was no pain score difference between multiheaded and single-head devices.

"Twenty adult patients were tested, utilizing 1mg/ml histamine on the arms and 6 mg/ml histamine on the back. Multi-test PC produced only three wheals less than 3 mm in diameter on the arm and none on the back, while ComforTen results showed 27 or nine times as many, arm and back. When averaging wheal sizes, wheals from Multi-Test PC were 50% larger than those from ComforTen. ComforTen was 14% more painful than Multi-Test PC."

Here are findings from the published work:

• Twenty adult patients were tested, utilizing 1 mg/ml histamine on the arms and 6 mg/ml histamine on the back.
• Results from the arms showed 18 wheals that were smaller than 3 mm for ComforTen, and only three wheals less than 3 mm for Multi-Test PC. This certainly raises an important issue of sensitivity.
• Results from the back showed nine wheals that were less than 3 mm in diameter for ComforTen and no wheals less than 3 mm in diameter for Multi-Test PC. Even at this high concentration of histamine, there is an issue of sensitivity.
• Multi-Test PC produced 57% larger wheals than ComforTen, when used on the arms, with mean wheal sizes of 6.25 mm vs. 4.0 mm respectively.
• Multi-Test PC produced 43% larger wheals than ComforTen even with the higher potency histamine, when used on the back, with mean wheal sizes of 7.15 mm vs. 5.02 mm respectively.
• Neither device produced wheals at any of the saline locations, but when averaging the pain factor, ComforTen was 14% more painful than Multi-Test PC.

In summary: Multi-Test PC generated much larger and easier-to-read reactions than ComforTen and a nearly insignificant number of wheals less than 3 mm when compared to ComforTen. While the differences in perceived pain were small, ComforTen produced more discomfort than Multi-Test PC.