Table 1. Details of algorithms used to identify patients with Stevens-Johnson syndrome and toxic epidermal necrolysis.

Algorithm domain and item (date required for each item)	Algorithm definition
	Set A	Set B	Set C	Set D
Domain 1) Diagnosis of SJS/TEN at the Department of Dermatology
Item 1. Records show ICD-10 code for SJS/TEN (L51.1 or L51.2) at the Department of Dermatology (admission and discharge date required)	yes	N/A	yes	N/A
Domain 2) Clinical course for SJS/TEN
Item 2: Hospitalizationa (admission and discharge date required)	yes/no	yes/no	yes/no	yes/no
Item 3: Skin biopsyb (date of biopsy required)	yes/no	yes/no	yes/no	yes/no
Item 4: Systemic treatments for SJS/TENc (order date required) Receiving any one of the following treatments: steroid therapy (≥0.5 mg/kg/day of prednisolone), intravenous immunoglobulin therapy, or plasma exchange therapy	yes/no	yes/no	yes/no	yes/no
Domain 3) Medical encounters for mucocutaneous lesions from SJS/TEN
Item 5: Medical encounters included any of the followingd (if any item is answered “yes”, Item 5 is considered as “yes”)	yes/no	yes/no	yes/no	yes/no
• Records of ICD-10 code for SJS/TEN at the Department of Ophthalmology or Dentistry, or for mucocutaneous lesionse (no limitation on department) (date of diagnosis with ICD-10 code required)
• Steroid eyedrops or ophthalmic ointmentf (order date required)
• Slit-lamp microscopy (date of microscopy required)
Domain 4) Exclusion of paraneoplastic pemphigus (either 6a or 6b)
Item 6a: Prescription of anti-cancer drugg (order date required)	yes/no	yes/no	N/A	N/A
Item 6b: Anti-desmoglein 1 or 3 antibody test ≥2h (execution date required)	N/A	N/A	yes/no	yes/no

SJS, Stevens-Johnson syndrome; TEN, toxic epidermal necrolysis; ICD-10, International Classification of Diseases, 10th Edition.

^a Inpatient treatment of SJS/TEN is recommended [2].

^b Establishing a diagnosis of SJS/TEN requires skin biopsy to determine massive epidermal degeneration [22].

^c Steroid therapy (≥0.5 mg/kg/day of prednisolone), intravenous immunoglobulin therapy (IVIg), or plasma exchange therapy are recommended for SJS/TEN patients in Japan [23–25].

^d Item 5 consists of the following three components relevant to medical encounters for mucocutaneous lesions, given that SJS/TEN often cause mucous membrane lesions, including ocular, oral and genital symptoms [1].

^e See S2 Table.

^f Steroid eyedrops or ophthalmic ointment are used for acute eye lesions [26, 27].

^g Since PNP is a complication of neoplasm, anti-cancer drugs are usually used for the neoplastic condition.

^h Differential diagnosis for PNP generally requires multiple testing of two times or more [28].