Long‐term preservation of direct immunofluorescence staining in slides stored at room temperature

To determine whether reproducible results from direct immunofluorescent tissue staining could be obtained after storing the slides at room temperature. We examined the original slides of 22 cases noted to be positive for direct immunofluorescence. Diagnoses include pemphigus, pemphigoid, lupus, dermatitis herpetiformis, lichen planus, and vasculitis. These specimens, initially evaluated during the period January 1997 to September 1998, were prepared with a standard immunofluorescence staining technique, and then a permanent aqueous mounting medium was added. All specimens were stored at room temperature in vertical slide holding trays. We focused on the presence and relative intensity of the immunofluorescence staining, as well as the final diagnosis. We then compared our readings to that of the original reports. Twenty of the 22 cases studied (91%) were read as having the same diagnosis as the initial immunopathology report. Seventeen of the 22 cases (77%) were found to have the identical or slightly less fluorescence intensity. The original reports in 3 of the cases did not comment on the original intensity of fluorescence. Thus, a comparison of fluorescence preservation could not be made. In 2 of the cases, the quality of tissue preservation was poor, and though fluorescent staining was noted, we were unable to render a diagnosis. Our results suggest that direct immunofluorescent studies, using a permanent aqueous mounting medium, can be stored over long periods of time at room temperature without significant degradation of staining.