What are the guidelines for using Lincoln Diagnostics products for skin testing?

Lincoln Diagnostics Multi-Test II Device for Allergy Skin Testing

The Multi-Test II device by Lincoln Diagnostics is a highly reliable and validated multiheaded skin testing device that demonstrates superior performance characteristics compared to other commercially available devices, with excellent reproducibility, high sensitivity (97-100%), and 100% specificity when using appropriate wheal size cutoffs. 1, 2, 3

Performance Characteristics

Sensitivity and Specificity

• Multi-Test II achieves 100% sensitivity and 97-100% specificity when using a 3-5mm wheal cutoff, making it one of the most accurate devices available 1, 2
• The device produces mean histamine wheal sizes of 7.47-9.23mm, which are consistently larger and more reliable than competing devices 1, 2
• For optimal diagnostic accuracy with Multi-Test II, a 5mm wheal size cutoff provides 99% specificity while maintaining excellent sensitivity 4

Reproducibility and Reliability

• Multi-Test II demonstrates low coefficient of variation (12.3-23.0%), indicating excellent test-to-test reproducibility 1, 2, 3
• The device shows minimal user variability (only 14% between different operators), making it reliable across different clinical settings 3
• All test head positions produce similar histamine wheal sizes with no statistically significant variation, ensuring consistent results regardless of which test head is used 1, 2

Proper Testing Technique

Preparation Requirements

• Discontinue antihistamines and tricyclic antidepressants several days before testing, as these medications suppress skin test responses 5, 6
• Oral and inhaled corticosteroids do not need to be discontinued 6
• Cleanse the skin with alcohol and allow to air dry before testing 7

Testing Procedure

• Use standardized allergen extracts when available to ensure accurate and reproducible results 5, 6
• Apply the Multi-Test II device to either the volar surface of the forearm or the patient's back 7, 3
• Use histamine base 1 mg/mL (Histamine Phosphate 2.75 mg/mL) as the positive control for percutaneous testing 7
• Read results at 15 minutes after application 5, 7

Interpretation

• Record measurements of both wheal and erythema for allergen sites and positive/negative controls 5, 6
• Document all medications the patient has taken within the past week 5
• Correlate positive skin test results with the patient's clinical history to assess clinical significance 5, 6

Comparative Advantages Over Other Devices

Superior to ComforTen Device

• Multi-Test II produces significantly larger mean wheal sizes (7.47mm vs 3.93mm) 1
• ComforTen has unacceptably low sensitivity (26% at 5mm cutoff, 82% at 3mm cutoff), which could result in underdiagnosis of allergy 1
• Multi-Test II has notably lower coefficient of variation (23.0% vs 40.5%), indicating better reproducibility 1

Superior to Skintestor Omni Device

• Multi-Test II produces more consistent wheal sizes (9.23mm vs 7.74mm mean) with lower variability 2
• Skintestor Omni produces significantly smaller wheals at certain test head positions, which can lead to false-negative results 2
• Multi-Test II maintains 100% sensitivity at both 3mm and 5mm cutoffs, while Skintestor Omni drops to 87% sensitivity at 5mm cutoff 2

Safety Considerations

Risk Profile

• Serious adverse events such as anaphylaxis are extremely rare with percutaneous skin testing 5
• No fatalities have been reported from prick/puncture inhalant testing 5
• Common reactions include local swelling, redness, pain, and itching at test sites 5

High-Risk Patients

• Patients with history of penicillin-related anaphylaxis, asthma, or those on beta-blockers should be tested in a monitored setting with emergency equipment available 5
• For patients who cannot undergo skin testing (extensive eczema, dermatographism, inability to discontinue antihistamines), consider in vitro IgE testing instead 5, 6

Clinical Context and Indications

• Skin prick testing with devices like Multi-Test II is indicated to confirm IgE-mediated allergic diseases, identify specific allergen sensitivities, and guide allergen immunotherapy 5, 6
• Skin testing is more sensitive and less expensive than blood testing, making it the preferred diagnostic method when feasible 5, 6
• Results must always be interpreted in conjunction with clinical history, as positive tests without corresponding symptoms may not be clinically significant 5