Numerous studies have compared the reliability and variability
of various devices.10–29 Analysis of the results of these
combined studies plus several recent prick/puncture comparative
studies does not reveal a clear-cut advantage for any
single or multitest device because interstudy results are variable.
This is partially due to the degree of trauma that the
device may impart to the skin, thereby accounting for different
sizes of positive reactions and even the possibility of
producing a false-positive reaction at the site of the negative
control. Thus, prick/puncture devices require specific criteria
for what constitutes a positive reaction (Table 2).27,30 What is
readily apparent from this table is the fact that wheal size
variability between the studies is highly significant at both
positive and negative test result sites.27 In addition, considerable
care should be given to proper training of skin test
technicians. To achieve quality assurance among technicians,
consistency in skin test performance should be demonstrated
by skin testing proficiency protocols. In Europe, a coefficient
variation of less than 20% after histamine control applications
has been suggested, whereas a coefficient variation of less
than 30% was used in a recent Childhood Asthma Management
Study.30 Table 3 outlines a suggested proficiency testing
protocol. Criteria (diameter or wheal area SD) for positive
and negative test results should be preestablished with the
device selected by each clinical test site. Under clinical
conditions, it is impossible to quantify the exact amount of