Direct immunofluorescence of plucked hair for evaluation of immunologic remission in pemphigus vulgaris

Background: Negative direct immunofluorescence (DIF) is a predictor of immunologic remission in pemphigus vulgaris. Recently, it has been shown that plucked hair can be used as substrate for DIF in the diagnosis of pemphigus.

Objective: We sought to compare hair DIF in patients with pemphigus vulgaris in clinical remission with conventional DIF for the assessment of immunologic remission.

Methods: A total of 55 patients with pemphigus vulgaris fulfilling the following inclusion criteria were enrolled: absence of any lesion and daily prednisolone dosage equal or less than 10 mg without adjuvant drug in the preceding 6 months. Biopsy specimen and plucked hair were processed for DIF. Intercellular deposition of IgG and/or C3 was considered positive.

Results: Conventional DIF and hair DIF were positive in 28 (50.9%) and 36 (65.5%) patients, respectively. Hair DIF had a sensitivity of 0.79 (95% confidence interval [CI] 0.59-0.92), a specificity of 0.48 (95% CI 0.29-0.68), a positive predictive value of 0.61 (95% CI 0.44-0.77), and a negative predictive value of 0.68 (95% CI 0.43-0.87).

Limitations: Small sample size is the main limitation of this study.

Conclusions: The sensitivity of hair DIF was not high enough to allow us to suggest it as a substitute for conventional DIF. On the other hand, one cannot disregard positive cases of hair DIF in the setting of negative biopsy DIF. As hair plucking is less invasive than biopsy, the following approach could be suggested: hair DIF may be repeated in patients in clinical remission until negative; then conventional DIF should be performed, too. The physician can decide to stop treatment only when DIF assays on both substrates are negative.