Evaluation of cytology collection techniques and prevalence of Malassezia yeast and bacteria in claw folds of normal and allergic dogs.

BACKGROUND Canine bacterial and Malassezia paronychia are common secondary complications of atopic dermatitis and adverse food reactions. HYPOTHESIS/OBJECTIVES The aim of this study was to compare three different sampling methods for claw fold cytology and to evaluate the numbers of bacteria, Malassezia yeast and inflammatory cells. ANIMALS Sixty client-owned dogs were classified into three groups: (A) normal dogs; (B) allergic dogs with no clinical evidence of claw disease (brown staining, erythema, swelling, crusts or exudates); and (C) allergic dogs with clinical paronychia. METHODS A prospective, blinded, split-plot study design was used. Claw folds from each dog were sampled using either a toothpick, tape preparation or direct impression smear. Slides were evaluated by two investigators for inflammatory cells, nuclear streaming, debris, corneocytes, yeast, intracellular (IC) cocci, extracellular (EC) cocci, IC rods and EC rods. For each parameter, data were compared between groups and between methods. Inter-reader agreements were calculated. RESULTS Group C had significantly higher values of EC cocci and corneocytes than Groups A or B. Although Malassezia organisms were more prevalent in allergic dogs than normal dogs, the counts were not significantly different. There were significantly higher numbers of Malassezia organisms (P = 0.0016) and EC cocci (P = 0.0106) retrieved from samples collected with a toothpick compared to other methods. Tape preparations were associated with significantly more debris and corneocytes (both P < 0.0001) and impression smears with significantly more nuclear streaming (P = 0.0468). CONCLUSIONS AND CLINICAL IMPORTANCE Sample collection using a toothpick optimizes the value of cytological results when sampling allergic dogs with clinical paronychia.