Multi-Test false-positive readings can be observed after deviation from product use instructions

Skin testing versus in vitro testing in the evaluation of aeroallergy: The great debate

When one examines reviews regarding diagnostic allergy testing, it generally is noted that the advantage of skin testing is that it uses testing to an end organ, is less expensive, is more sensitive, and provides immediate results, which are easily visualized by the patient. In the case of in vitro testing, it is thought to be more helpful for patients with dermographia or widespread dermatitis, is not affected by H1 or H2 antagonists, and is thought to be safer than skin testing. This may not be entirely correct because studies actually demonstrated phlebotomy to be associated with more morbidity than skin-prick testing. Other concerns regarding both tests include allergen quality, the need from proficiency testing, and the fact that these tests should be used for corroborating a diagnosis as opposed to a screening test for allergy.

Skin testing

OBJECTIVE

To provide the reader with a relevant review of the literature regarding skin testing in the allergist's office.

DATA SOURCES

A PubMed search for the years 1970 through 2005 was performed using the following keywords: allergy skin testing, skin prick testing, and intradermal skin testing.

STUDY SELECTION

Articles that highlighted aspects of sentinel to clinical allergists' use of skin testing in the office, such as methods of skin testing, intradermal vs skin prick testing, skin test devices, and methods of expressing skin test results, were selected for further review.

RESULTS

Skin testing remains the central test to confirm an allergic response. It is minimally invasive and when performed correctly has good reproducibility. Results are easily quantifiable and correlate well with end organ challenge. It is imperative however that technicians who perform the skin tests and the clinicians who order or interpret these tests understand the characteristics of the specific tests they are administering. It is also important that the clinician express skin test results in a manner that allows easy interpretation by another physician.

CONCLUSIONS

Allergists must consider controllable variables that affect skin test results and their interpretation. When not considered, they may be responsible for some of the inaccuracies associated with allergy skin testing.

Comparison of the sensitivity and precision of four skin test devices

Twenty volunteers were skin tested with seven concentrations of histamine phosphate and a glycerosaline control to determine the relative sensitivity and precision of four skin test devices: Greer Pen (GP), Greer DermaPIK (DP), Center Multi-Test (MT), and Morrow Brown needle (MB). The end points of the study were (1) wheal and flare response of each device, with a dose-response curve, (2) the time required to apply each set of eight tests, and (3) the volunteers' subjective assessment of each device. On a different day, 10 of the volunteers were tested to determine the precision of each device. Dose-response curves for half-log dilutions of histamine phosphate were produced with a glycerosaline control. The DP and GP induced wheal and flare responses discernible from that of the glycerosaline control at a lower concentration of histamine phosphate than the MB and MT. The DP took a shorter time to apply eight samples than any other device. The MB was preferred by the most volunteers, but any device tested on the upper half of the back was usually preferred over that tested on the lower half. When 5 mg/ml histamine phosphate was used, coefficients of variation for each device demonstrated that for wheals the precision of the DP, GP, and MT was similar (mean, 21.1%, 23.1%, and 24.5%, respectively). The MB was larger (mean, 59.9%). For flares, the precision of GP and DP was similar (mean, 22.0% and 23.5%, respectively), with the MT and MB larger (mean, 35.5% and 58.2%, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)