O'Grady 1990.

Study characteristics
Patient sampling	Prospective, consecutive admissions over the 24 hours of the chosen research day, one day each week for one year.
Patient characteristics and setting	N included in study: 109. N in analysis: 99. Age: Mean 40.6, range 18‐89 years. Gender: M 40, F 59. Ethnicity: Not reported. Comorbid disorders: Not reported. Duration of symptoms: Not reported. Concurrent medications used: Not reported. Inclusion criteria: Patients admitted to the acute admission wards, in hospital for a minimum of four days, but in practice, no patient was excluded by staying less than four days. Exclusion criteria: Patients admitted to psychogeriatric admission wards. Patients profoundly deaf or unable to speak English. Study aim: To find the frequencies of broadly and narrowly defined FRS in a sample of acute mental hospital admissions and find how they relate to diagnosis. Previous treatment for schizophrenia: Not reported. Clinical setting: Inpatients. Country: UK.
Index tests	Description of FRS used: A FRS questionnaire was added on to the SADS. The symptom questionnaire contained questions on all 11 first‐rank symptoms. Each symptom was rated using the dichotomy of wide versus narrow definitions proposed by Koehler (1979). The various definitions were drawn from Mellor (1970), Fish (1967), Wing et al (1974), and Taylor and Heissler (1971).The narrow definition was in all cases that of Mellor (1970). Professionals performing test: "Researcher" Resolution of discrepancies: Not reported. How FRS used in study: Diagnosis.
Target condition and reference standard(s)	Reference standard: A semi‐structured interview, the Schedule for Affective Disorders and Schizophrenia (SADS), was used for each participant. Then diagnoses were assigned using the Research Diagnostic Criteria (RDC), Carpenter's Flexible System, and the New Haven Index. Target condition(s): Schizophrenia, schizoaffective manic, schizoaffective depressed, manic disorder, hypomanic disorder, major depressive disorder, minor depressive disorder, other (not specified). Professionals performing test: "Researcher". Resolution of discrepancies: Not reported.
Flow and timing	Study process: Participants were interviewed on one day each week over a year, excluding breaks for holidays. All admissions over the 24 hours of the chosen research day were interviewed. Each participant was interviewed using the Schedule for Affective Disorders and Schizophrenia (SADS) with an additional FRS questionnaire. Diagnoses were then assigned using the Research Diagnostic Criteria (RDC), Carpenter's Flexible System, and the New Haven Index. The reference standard and index test were applied during the same interview. Follow‐up: Not reported. Exclusion: "Three [patients] refused to be interviewed and three interviews were not suitable for research purposes. In these six cases there was no evidence of first‐rank symptoms from interview or scrutiny of case notes. Four patients had organic brain disease and are not included in the main sample as they were not suitable for interview using the SADS."
Comparative
Notes	The SADS was used as it is specifically structured to provide RDC diagnoses. Carpenter's Flexible System and the New Haven Index were used as they do not heavily rely on first rank symptoms (FRS) to define schizophrenia. Only data from the RDC is usable in the analysis.
Methodological quality
Item	Authors' judgement	Risk of bias	Applicability concerns
DOMAIN 1: Patient Selection
Was a consecutive or random sample of patients enrolled?	Unclear
Was a case‐control design avoided?	Yes
Did the study avoid inappropriate exclusions?	Yes
		Unclear	Low
DOMAIN 2: Index Test All tests
Were the index test results interpreted without knowledge of the results of the reference standard?	Yes
Did the study pre‐specify whether they were using one or multiple FRSs?	No
		Unclear	Low
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?	No
		High	Low
DOMAIN 4: Flow and Timing
Was there an appropriate interval between index test and reference standard?	Yes
Were all patients included in the analysis?	No
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