Carpenter 1974.

Study characteristics
Patient sampling	Prospective, consecutive (unclear whether consecutive for patients with neurotic depression).
Patient characteristics and setting	N with a clinical diagnosis of psychosis: 1202. N screened: 1119. Age: Not reported. Gender: Not reported. Ethnicity: Not reported. Comorbid disorders: Not reported. Duration of symptoms: Not reported. Concurrent medications used: Not reported. Inclusion criteria: Between the ages of 15 and 45. Had one of the following symptoms: delusions, other disordered thinking, hallucinations, inappropriate or bizarre behavior, gross psychomotor disorder, severe affect disorder, depersonalisation, self‐neglect, social withdrawal, over­whelming fear, or a diagnosis of psychosis on admission. The "aim of Phase 2 was for each Centre to collect at least 125 cases of functional psychosis" "In addition to the 125 cases of functional psychosis, it was decided that 10 cases of neurotic depression should also be included in order to provide extra material for differential diagnosis." Exclusion criteria: Evidence of organic disease, hospitalised for more than two or psychotic for more than three of the last five years. Study aim: The International Pilot Study of Schizophrenia (IPPS) was a long‐term epidemiological study funded by WHO with broader aims, among them to evaluate the prevalence and frequency of FRS in schizophrenia, and whether FRS are pathognomonic of schizophrenia in the absence of "organic psychosis". Previous treatment for schizophrenia: Not reported. Clinical setting: Inpatients. Country: China (Taiwan), Colombia, Czechoslovakia, Denmark, India, Nigeria, USSR, UK, USA.
Index tests	Description of FRS used: PSE interview schedule used. Nine of the 11 FRSs (delusional percept and somatic passivity omitted as not adequately defined in the PSE). Two FRSs were not systematically assessed in US and were omitted from the analysis of American patients. One PSE interview item covered both "made impulses" and "made feelings" so these two symptoms were grouped together in the analysis. One or more FRSs needed for a diagnosis of schizophrenia. Only ratings indicating that a symptom was definitely present were considered positive, and all other ratings, including "questionably present" were considered negative. Professionals performing test: One psychiatrist. Resolution of discrepancies: Only one psychiatrist made each diagnosis. In order to check the reliability of their diagnoses, at least one interview was conducted each month with two psychiatrists rating. How FRS used in study: Diagnosis.
Target condition and reference standard(s)	Reference standard: International Statistical Classification of Diseases (ICD‐8) using the PSE interview and a psychiatric history and a social description interview. In the USA subsample, diagnoses were made according to the Diagnostic and Statistical Manual (DSM‐II). Target condition(s): Schizophrenia, manic psychosis, neurosis and personality disorders. Professionals performing test: One psychiatrist. Resolution of discrepancies: Only one psychiatrist made each diagnosis. In order to check the reliability of their diagnoses, at least one interview was conducted each month with two psychiatrists rating.
Flow and timing	Study process: All patients contacting each of the Field Research Centres were put through two screens, a demographic screen and a psychotic screen. Once included, they were given the PSE, past history was obtained, then a diagnosis was made using the ICD or DSM‐II (USA subsample). FRS were assessed in the PSE interview. Follow‐up: 2 years.
Comparative
Notes	[See page 8 of WHO report for details of methods.] Study part of the International Pilot Study of Schizophrenia (IPSS).
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?	Unclear
		Unclear	Low
DOMAIN 2: Index Test All tests
Were the index test results interpreted without knowledge of the results of the reference standard?	No
Did the study pre‐specify whether they were using one or multiple FRSs?	Yes
		High	Low
DOMAIN 3: Reference Standard
Is the reference standards likely to correctly classify the target condition?	Yes
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?	No
Did all patients receive the same reference standard?	No
Did all patients receive an index test?	Yes
Did all patients receive the same index test?	No
		High