A semi-structured clinical interview for psychosis sub-groups (SCIPS): development and psychometric properties

Abstract

Background

Clinical sub-groups of schizophrenia, namely drug related, traumatic, anxiety and stress sensitivity sub-types, have been proposed for use in research, training and practice. They were developed on the basis of clinical observation but have not yet been used in research or clinical practice to any great extent.

Aims

To develop a semi-structured clinical interview for psychosis sub-groups (SCIPS) and determine the best diagnostic criteria with the highest inter-rater reliability, test–retest reliability and concurrent validity for sub-grouping patients with schizophrenia according to a newly developed classification scheme.

Methods

The SCIPS was developed based upon discussion with the clinician researchers who had developed and were using the sub-groups. Kappa coefficients were calculated between two independent diagnostic assessments with the SCIPS (for inter-rater reliability and test–retest reliability, n = 20) and between the SCIPS diagnosis and the sub-groupings as determined independently with highest achievable validity (for concurrent validity, n = 21) for patients with schizophrenia. These inter-rater reliability and concurrent validity were compared among five different sets of diagnostic criteria to determine which was most reliable and valid.

Results

A set of diagnostic criteria with the highest inter-rater reliability and concurrent validity was determined. Kappa coefficients (95% confidence interval) for the inter-rater reliability and concurrent validity were 0.93 (0.66–1.20) and 0.73 (0.47–1.00), respectively, with these diagnostic criteria.

Conclusions

The SCIPS is a promising tool with which to sub-group patients with schizophrenia according to this recently developed classification scheme. The semi-structured interview achieves acceptable inter-rater and test–retest reliability and concurrent validity.

Appendices

Appendix 1: Semi-structured clinical interview for psychosis sub-groups (SCIPS)

Instructions

This interview is semi-structured, and the interviewer may use additional questions and prompts to collect the required information.

In order to sub-group a patient, the “SCIPS interview” is completed first. Then, the “Rating sheet for the SCIPS” is completed according to the results of the interview. Finally, the “Diagnostic criteria for the SCIPS sub-groups” is used to sub-group the patient. Whenever an interviewer finds a difficulty in rating, Appendix 1.3, “The diagnostic guidelines for psychosis sub-types”, can be referred to clarify what should be rated for each item.

Appendix 1.1: The social readjustment rating scale and questionnaire by Holmes & Rahe (life change unit ≥40)

 

Life experience	Life change units
Death of spouse	100
Divorce	73
Marital separation	65
Jail term	63
Death of close family member	63
Personal injury or illness	53
Marriage	50
Fired at work	47
Marital reconciliation	45
Retirement	45
Change in health of family member	44
Pregnancy	40
Sex difficulties	39
Gain of new family member	39
Business readjustment	39
Change in financial state	38
Death of close friend	37
Change to different line of work	36
Change in number of arguments with spouse	35
Large mortgage	31
Foreclosure of mortgage or loan	30
Change in responsibilities at work	29
Son or daughter leaving home	29
Trouble with in-laws	29
Outstanding personal achievement	28
Wife begins or stops work	26
Begin or end school	26
Change in living conditions	25
Revision of personal habits	24
Trouble with boss	23
Change in work hours or conditions	20
Change in residence	20
Change in schools	20
Change in recreation	19
Change in church activities	19
Change in social activities	18
Small loan	17
Change in sleeping habit	16
Change in number of family get-togethers	15
Change in eating habits	15
Vacation	13
Christmas	12
Minor violation of the law	11

Appendix 1.2: Diagnostic criteria for borderline personality disorder in DSM-IV

A pervasive pattern of instability of interpersonal relationships, self-image, and affects, and marked impulsivity beginning by early adulthood and present in a variety of contexts, as indicated by five (or more) of the following:

• (1) Frantic efforts to avoid real or imagined abandonment. Note: do not include suicidal or self-mutilating behaviour covered in Criterion 5.

• (2) A pattern of unstable and intense interpersonal relationships characterised by alternating between extremes of idealisation and devaluation.

• (3) Identity disturbance: markedly and persistently unstable self-image or sense of self.

• (4) Impulsivity in at least two areas that are potentially self-damaging (e.g., spending, sex, substance abuse, reckless driving, binge eating). Note: do not include suicidal or self-mutilating behaviour covered in Criterion 5.

• (5) Recurrent suicidal behaviour, gestures, or threats, or self-mutilating behaviour

• (6) Affective instability due to a marked reactivity of mood (e.g., intense episodic dysphoria, irritability, or anxiety usually lasting a few hours and only rarely more than a few days).

• (7) Chronic feelings of emptiness

• (8) Inappropriate, intense anger or difficulty controlling anger (e.g., frequent displays of temper, constant anger, recurrent physical fights)

• (9) Transient, stress-related paranoid ideation or severe dissociative symptoms

Appendix 1.3: Diagnostic guidelines for psychosis sub-types

Drug-related psychosis

Core characteristics

The person has used at least one of the stimulants/hallucinogens which are listed below in the 2 weeks before the onset of psychotic symptoms.

List of hallucinogens:

Amphetamine, cocaine, LSD, ecstasy, cannabis, others¹

Supporting characteristics

Age of onset:

• Usually in their teens or 20 s.

Mode of onset²:

• Either acute or insidious.

Lifetime pattern of social interaction:

• Individuals with this sub-type are relatively sociable, having many friends at school and may have partners or spouses.

Symptom pattern:

• Symptom patterns tend to be diverse.

• Negative symptoms tend to be less prominent with this sub-type.

Traumatic psychosis

Core characteristics

The person meets the criteria for co-morbid borderline personality disorder and has experienced childhood sexual or emotional abuse.

Supporting characteristics

Age of onset:

• Usually in their teens or 20 s.

Mode of onset:

• Either acute or insidious.

Lifetime pattern of social interaction:

• Individuals with this sub-type have chaotic relationships with others (e.g., severe conflict with their families, unstable sexual relationships with many boy/girlfriends).

Symptom pattern:

• Abusive hallucinations (auditory or visual) are frequent.

Anxiety psychosis

Core characteristics

The person has had good peer relationships in early adolescence and usually developed close relationships with a partner or spouse.

Supporting characteristics

Age of onset:

• Usually in their 30 s or older.

Mode of onset:

• Acute.

Individuals have experienced stressful life events which have immediately preceded psychotic symptoms within 3 months.

• Lifetime pattern of social interaction:

• Individuals with this sub-type are relatively sociable, having friends at school and partners or spouses in adulthood.

Symptom pattern:

• Delusions, especially systematised (well organized) delusions, are generally prominent.

• Hallucinations (auditory, visual, or with other modals) can occur but are less prominent.

• Negative symptoms tend to be less prominent with this sub-type.

Stress sensitivity psychosis

Core characteristics

The person is more stress sensitive³ and less sociable.

Supporting characteristics

Age of onset:

• Usually in their teens or early 20 s.

Mode of onset:

• Insidious.

Lifetime pattern of social interaction:

• Individuals with this sub-type are less sociable, having few friends in their childhood and adolescence, and they do not have partners or spouses prior to developing symptoms.

Symptom pattern:

• Negative symptoms are prominent, even in the first episode.

A diverse range of positive symptoms occur.