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. 2016 Sep 21:6:36.
doi: 10.1186/s13601-016-0126-7. eCollection 2016.

Proficiency testing of skin prick testers as part of a quality assurance system

Hans-Jørgen Malling  1 , Pernille Allesen-Holm  1 , Lisbeth Sys Karved  1 , Lars K Poulsen  1
Affiliations

Proficiency testing of skin prick testers as part of a quality assurance system

Hans-Jørgen Malling et al. Clin Transl Allergy. .

Abstract

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.

Conclusion: The described histamine testing provides an objective system for the evaluation of basic skin test quality assessment standards especially for documentation in scientific studies.

Keywords: Coefficient of regression; Coefficient of variation; Histamine skin prick test; Quality assessment; Reproducibility.

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Figures

Fig. 1
Fig. 1
The coefficient of variation of 8-double histamine wheal areas. a depicts the results of 3 mg/ml; b 10 mg/ml; c 30 mg/ml and d 100 mg/ml histamine. The solid line indicates the upper limit (CV < 40 %) for acceptance (4,5) while the dotted line represents the CV of 20 % (highly qualified tester)
Fig. 2
Fig. 2
Mean wheal area (square millimetres) of the 8 repeats of each of the 4 different concentrations of histamine of the 14 nurses tested. Histamine concentrations as in Fig. 1
Fig. 3
Fig. 3
Dose-response curves of wheal area vs histamine concentration of all 14 tested operators. The median slope is 0.217 corresponding to almost a doubling of the wheal area by increasing the histamine concentration by a factor 10
See this image and copyright information in PMC

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