Proficiency testing of skin prick testers as part of a quality assurance system.
BACKGROUND
Skin prick test is an important diagnostic procedure in clinical allergy but documentation of the quality is often missing.


METHODS
We describe a proficiency system to evaluate staff members in relation to the international recommended reproducibility in terms of coefficient of variation (CV < 40 %) and the linearity (coefficient of regression >0.85) based on blinded octuplicate histamine testing using histamine 3, 10, 30 and 100 mg/ml.


RESULTS
Fourteen trained allergy nurses participated in the proficiency testing. More than 95 % of the nurses, generated coefficient of variation less than 40 %, and for around 35 % of testers the CV were below 20 % based on wheal area. Regarding the linearity (coefficient of regression), only two nurses produced tests with a value below 0.85. On the contrary, 79 % of testers demonstrated a coefficient of regression >0.95. Depending on the gentleness of the prick procedure, the inter-nurse variability in wheal area varied more than twofold corresponding to a 10-doubling of histamine concentration. This would never have been detected without using a proficiency testing system.


CONCLUSIONS
The described histamine testing provides an objective system for the evaluation of basic skin test quality assessment standards especially for documentation in scientific studies.
Allergy Clinic, Copenhagen University Hospital Gentofte, Kildegårdsvej 28, 2900 Hellerup, Denmark.
Hans-Jørgen
0000-0003-4868-6307
HJ
Malling
Allergy Clinic, Copenhagen University Hospital Gentofte, Kildegårdsvej 28, 2900 Hellerup, Denmark.
Pernille
P
Allesen-Holm
Allergy Clinic, Copenhagen University Hospital Gentofte, Kildegårdsvej 28, 2900 Hellerup, Denmark.
Lisbeth Sys
LS
Karved
Allergy Clinic, Copenhagen University Hospital Gentofte, Kildegårdsvej 28, 2900 Hellerup, Denmark.
Lars K
LK
Poulsen
Coefficient of regression; Coefficient of variation; Histamine skin prick test; Quality assessment; Reproducibility
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