Comparison of three different techniques for application of water solutions to Finn Chambers®.

BACKGROUND With regard to contact allergy, the dose of a sensitizer per unit skin area is an important factor for both sensitization and elicitation, and therefore a known amount/volume of test preparation should be applied at patch testing. OBJECTIVES To compare three different techniques for the application of aqueous solutions to Finn Chambers, in order to determine the precision and accuracy of each technique when the recommended 15 µl volume is applied. METHODS Four technicians applied formaldehyde 1.0% aq. (wt/vol) and methylchloroisothiazolinone/methylisothiazolinone 200 ppm (wt/vol) in sets of 10 onto Finn Chambers, with three different techniques: (i) micro-pipetting; (ii) dripping the solutions; and (iii) dripping the solutions followed by removal of excess solution with a soft tissue. Assessment of the variations was performed with the use of descriptive data. The ability to apply the exact amount was assessed by Fisher's exact test by categorizing each application as in or out of the range 12-18 µl. RESULTS/CONCLUSIONS The micro-pipette technique had the best accuracy and precision, as well as the lowest inter-individual variation. The technique in which excess solution was removed had good precision, but failed in the application of the defined amount, i.e. 15 µl.