The Efficacy of Sample Storage Envelopes in Collecting Scales From the Skin and Nails for Mycology Laboratory Diagnosis of Superficial Fungal Infection.

Background: Fungal cultures are unavailable in many hospitals. The development of an effective sample storage solution for timely transportation would improve management of patients with superficial fungal skin and nail infections. Objectives: This study aimed to evaluate the efficacy of sample storage envelopes to preserve skin and nail samples for timely microscopic examination and culture for superficial fungal infections. Methods: Patients aged 18 years and above with suspected superficial fungal infections were enrolled. The samples were divided into four envelopes. The baseline 20% potassium hydroxide (KOH) examination and fungal culture served as reference points. The stored samples were reexamined on Days 3, 7, 14, and 28. Results: The study included 90 patients with suspected superficial fungal infections (45 skin and 45 nail lesions). Reference KOH examinations showed branching septate hyphae in 36 (80.0%) for skin and 35 (77.8%) for nail infections. Reference fungal cultures were positive for the growth of dermatophyte and nondermatophyte molds in 34 (75.6%) and 28 (62.2%) in skin and nail infections, respectively. Sample storage envelopes maintained 100% sensitivity and specificity for up to 28 days with KOH examination for both skin and nail samples. On Day 28, the fungal culture sensitivity was 70.6% for the skin and 64.3% for the nail samples, with specificities of 100.0% and 88.2%, respectively. Conclusions: Sample storage envelopes effectively maintained diagnostic accuracy for up to 28 days with KOH examination for both skin and nail samples. Given the high specificity even on Day 28 for fungal culture, transferring samples within 28 days remains a reliable practice.