Comparison of cytological findings between direct impression smears and adhesive slides in canine superficial bacterial folliculitis.

Background: Cutaneous cytological investigation is a valuable tool for the diagnosis of superficial bacterial folliculitis (SBF). Studies comparing tape strips and direct impression (DI) smears have demonstrated that DI may recover more inflammatory cells and nuclear streaming (NS). Adhesive slides (AS) have not been evaluated in cutaneous cytological investigation.

Objective: To compare cytological findings between AS and DI for the same lesion in SBF.

Animals: Fifteen client-owned dogs with clinical signs suggestive of SBF were enrolled.

Materials and methods: Fifty lesions consistent with SBF comprising collarettes, papules and crusts were included. Half of each lesion was sampled using DI and the other half sampled using AS. Papules were sampled sequentially in a randomised order between techniques. Three investigators blinded to the sample pairings read the slides in duplicate. Ten adjacent oil immersion fields were examined. Bacteria were recorded on a quantitative scale, polymorphonuclear cells (PMN), NS and 'miscellaneous' on a qualitative scale, and keratinocytes (KC) on a semiquantitative scale.

Results: Significant differences were identified for KC (DI mean 2.5, SD ±0.08; AS mean 3.3, SD ±0.06, p < 0.0001), 'miscellaneous' (DI mean 0.72, SD ±0.03; AS mean 0.83, SD ±0.02 p < 0.0001), NS (DI mean 0.69, SD ±0.03; AS mean 0.56; SD ±0.03, p < 0.0001) and extracellular cocci (DI mean 5.03, ±SD 7.2; AS mean 3.91, ±SD 4.3, p = 0.01).

Conclusions and clinical relevance: DI identified more EC cocci and NS, while AS detected more KC and debris. Intra- and interobserver agreement varied, with AS having poorer agreement for several parameters. These results can be used to inform the clinician of the best methodology to use in confirming a diagnosis of SBF.