Revisiting serum storage protocols: assessing the impact of temperature variations on indirect immunofluorescence testing for pemphigus and bullous pemphigoid.

ABSTRACT

BACKGROUND: Indirect immunofluorescence (IIF) plays a crucial role in the diagnosis of pemphigus and bullous pemphigoid (BP) by detecting the presence of circulating autoantibodies in the serum of patients. The standard serum transportation method requires delivery to laboratories at 2-8 °C within a day and storage at -20 to -80 °C. However, this protocol poses logistical challenges. OBJECTIVES: We conducted a study to assess how temperature variations affect the effectiveness of IIF tests. METHODS: This case-control study analysed 203 serum specimens 102 from patients with pemphigus and 101 from patients with BP. Specimens were stored at -80 °C (control), 24 °C, and 40 °C for seven days before analysis to investigate variations in IIF titres compared to the control conditions. RESULTS: In pemphigus serum, 95% at 24 °C and 76% at 40 °C showed no titre difference compared to controls. Similarly, 89% of BP serum at 24 °C and 82% at 40 °C matched the control titres. While 57 specimens across both groups experienced reduced titres, the decrease was primarily marginal (one-step reduction in 54 cases, two-step in 3), with no transition from positive to negative results. CONCLUSIONS: Storing serum at 24-40 °C for up to seven days before testing slightly influences IIF outcomes for pemphigus and BP. These findings could prompt a significant revision in the existing strict transport guidelines, ensuring efficient use of resources without sacrificing the accuracy of diagnostic tests.