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Objective:To evaluate the value of indirect immunofluorescence on salt-split skin (IIF-SSS) in the diagnosis of bullous pemphigoid (BP) .Methods:A single-center clinical retrospective study was conducted. Totally, 163 patients with newly diagnosed BP were collected from Hospital of Dermatology, Chinese Academy of Medical Sciences from January 2013 to January 2019, so were 404 controls, including 161 with pemphigus, 67 with eczema, 26 with drug eruption, 23 with erythema multiforme, 18 with prurigo nodularis, etc. Blood samples were collected before the treatment, and IIF-SSS, BP180 NC16A enzyme-linked immunosorbent assay (ELISA) and direct immunofluorescence (DIF) assay were performed to evaluate the value of IIF-SSS in the diagnosis of BP. Measurement data were compared by using t test and Mann-Whitney test, and enumeration data were compared by using chi-square test and Fisher′s exact test or McNemar test. Results:The number of cases positive for IIF-SSS, BP180 NC16A ELISA and DIF assay was 160, 153 and 127 respectively in the BP group, and 0, 18 and 26 respectively in the control group. The sensitivities of IIF-SSS, BP180 NC16A ELISA and DIF assay for the diagnosis of BP were 98.15%, 93.86% and 77.91% respectively, and their specificities were 100%, 95.54% and 93.56% respectively. There was strong consistency in the diagnosis of BP between IIF-SSS and DIF (Kappa coefficient= 0.767, P < 0.001) . Conclusion:IIF-SSS has relatively high sensitivity and specificity for the diagnosis of BP, and can serve as a routine method for diagnosing BP.
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Objective:To optimize indirect immunofluorescence on salt-split skin (IIF-SSS), and to evaluate its performance in detection of bullous pemphigoid (BP) antibodies.Methods:Normal human foreskin and non-foreskin skin tissues were used to prepare salt-split substrates under 3 different experimental conditions: traditional group rotated at 4 ℃ for 48 - 72 hours, low-temperature immersion group soaked at 4 ℃ for 48 - 72 hours, room-temperature immersion group soaked at 25 ℃ (range: 23 - 27 ℃) for 24 hours. Serum samples were obtained from 20 patients with bullous pemphigoid (BP) in Hospital of Dermatology, Chinese Academy of Medical Sciences between August 2019 and August 2020, and subjected to IIF on the intact skin or salt-split substrates by using a multiple dilution method. Paired-sample t test was used for comparisons of means between two paired samples. Results:No dermal-epidermal separation was observed in the substrates prepared in the low-temperature immersion group at 48 - 72 hours, while dermal-epidermal separation occurred in the lower lamina lucida of the foreskin and non-foreskin substrates in the room-temperature immersion group and the traditional group. For the 20 patients with BP, the reciprocal end-point titers ( M[ Q1, Q3]) detected with the salt-split non-foreskin skin and salt-split foreskin in the room-temperature immersion group, and with the salt-split non-foreskin skin in the traditional group were 5 120 (2 560, 17 920), 1 280 (640, 2 560), 1 280 (640, 2 560), respectively. Moreover, 19 (95%) patients with BP showed that the reciprocal end-point titers detected with the substrates in the room-temperature immersion group were 1 - 5 times those in the traditional group ( t = 8.04, P<0.001), suggesting that the performance of salt-split skin in the room-temperature immersion group was superior to that in the traditional group in the detection of BP antibodies; however, there was no significant difference in the reciprocal end-point titers of BP antibodies between the salt-split foreskin in the room-temperature immersion group and salt-split non-foreskin skin in the traditional group ( t<0.001, P>0.05). The reciprocal end-point titers in 20 BP sera detected by conventional IIF on the intact non-foreskin skin and foreskin were 320 (160, 640) and 480 (160, 1 120), respectively; the reciprocal end-point titers detected by IIF on the salt-split foreskin and non-foreskin skin in the room-temperature immersion group, as well as on the salt-split non-foreskin skin in the traditional group, were all consistent with or 1 - 7 times higher than those detected by conventional IIF ( t = 6.47, 14.83, 5.26, respectively, all P<0.001) . Conclusion:The soaking method at room temperature 25 ℃ (23 - 27 ℃) for preparing salt-split substrates has advantages of short duration and simple procedure, and the sensitivity of IIF-SSS using the substrates prepared by this method is equal or superior to the traditional salt-split method for detecting BP antibodies.
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Epidermolysis bullosa acquisita(EBA) is a rare chronic subepidermal bullous disease wit,h autoantibodies to type VII collagen. Clinically, EBA usually begins after the age of 50 with pruritic vesicle and blister formation often on traumatized skin and leaves atrophic scars and milia. A 48-year-old woman visited our department with a 5 month history of a generalized pruritic blistering eruption that began on the scalp and spread to the face, trunk, extremities, and lip. The biopsy specimen revealed dermoepidermal separation, infiltration of perivascular mononuclear cells. Direct immunofluorescence(DIF) showed positive linear deposition of IgG at the BMZ. Bullous pemphigoid was diagnosed and treated with prednisolone 20-40mg daily. The skin lesions were improved after 2 week. During follow-up, trauma-induced vesicles occurred frequently and healed with remaining malia and scars. The biopsy specimen of trauma induced vesicles revealed subepidermal blisters and inflammatory cell infiltration in the dermis. DIF of perilesional skin showed positive linear deposition of IgG at the BMZ. DIF of salt split skin showed linear IgG deposits on the dermal floor. EBA was confirmed.