The precision of intracutaneous skin test with timothy pollen allergen preparation using two different techniques

The precision of two intracutaneous skin test techniques was investigated by testing three grass pollen-sensitive patients. Twenty tests were performed on the back of each patient with each of two techniques. One method used a glass syringe with a 26 G precision needle attached to micrometer equipment. The other method used a disposable 1-mL plastic syringe with a disposable 20 G needle. The tests were arranged in five rows. Each row consisted of two pairs of tests on each side of the spine. Each pair was considered as duplicate tests at the same site. The two methods were tested on either side of the back. No difference in precision between the techniques was found. The analysis revealed differences in skin reactivity between different areas of the back of individual patients but without a common pattern between patients. These differences, therefore, will not influence test results if several patients are included in the investigation, eg, of the relative potency of allergenic extracts and the allocation of test sites is consistent. The variation found, however, will influence comparisons within the same patient, but in an unpredictable way.