Tandon 1987.

Study characteristics
Patient sampling	Prospective, consecutive.
Patient characteristics and setting	N included in study: 294. N screened: 294. Age: Not reported. Gender: Not reported. Ethnicity: Not reported. Comorbid disorders: Not reported. Duration of symptoms: Not reported. Concurrent medications used: "Off all medication for at least 2 weeks." Inclusion criteria: Having "undergone a comprehensive SADS interview by a trained clinician in the course of the inpatient stay after having been off all medication for at least 2 weeks". Exclusion criteria: Not reported. Study aim: The prevalence of Schneiderian first‐rank symptoms (FRS) to their diagnostic distribution (SAD, RDC). Previous treatment for schizophrenia: Not reported. Clinical setting: Inpatients. Country: USA.
Index tests	Description of FRS used: "Presence or absence of first‐rank symptoms was established on the basis of the standardized SADS interview." "Patients with two or more FRS received a diagnosis of schizophrenia." Only 9 FRS's reported (not predefined) in table, with Delusional perception as" not documented". Professionals performing test: SADS interview by a trained clinician. Resolution of discrepancies: Not reported. How FRS used in study:Prevalence.
Target condition and reference standard(s)	Reference standard: Research Diagnostic Criteria (RDC). Target condition(s): Major depressive disorder, primary major depressive disorder (MDD), substance abuse with toxic psychosis with secondary MDD, schizophrenia, schizoaffective disorder, manic disorder, minor depressive disorder. Professionals performing test: Not reported. Resolution of discrepancies: Not reported.
Flow and timing	Study process: "All admissions to a unit for affective disorders at the University of Michigan Medical Center" over 8 years were reviewed, and anyone who had "undergone a comprehensive SADS interview by a trained clinician in the course of the inpatient stay" was included. These patients were screened for the presence of first‐rank symptoms at the time of the baseline evaluation through SADS. No details about when or how RDC diagnosis was assessed. Follow‐up: Not reported. Exclusions: Not reported.
Comparative
Notes	Unclear when Reference standard was assessed. FRS symptoms not pre‐defined. All patients with two or more FRS received a diagnosis of schizophrenia however no differentiation made between the diagnosis of more than 1 FRS.
Methodological quality
Item	Authors' judgement	Risk of bias	Applicability concerns
DOMAIN 1: Patient Selection
Was a consecutive or random sample of patients enrolled?	Yes
Was a case‐control design avoided?	Yes
Did the study avoid inappropriate exclusions?	Unclear
		Unclear	High
DOMAIN 2: Index Test All tests
Were the index test results interpreted without knowledge of the results of the reference standard?	Unclear
Did the study pre‐specify whether they were using one or multiple FRSs?	Yes
		Unclear	High
DOMAIN 3: Reference Standard
Is the reference standards likely to correctly classify the target condition?	Unclear
Were the reference standard results interpreted without knowledge of the results of the index tests?	Unclear
		Unclear	Low
DOMAIN 4: Flow and Timing
Was there an appropriate interval between index test and reference standard?	Unclear
Were all patients included in the analysis?	Yes
Did all patients receive a reference standard?	Yes
Did all patients receive the same reference standard?	Yes
Did all patients receive an index test?	Yes
Did all patients receive the same index test?	Yes
		Low