Generalizability studies of the Global Assessment of Functioning–Split version

doi:10.1016/j.comppsych.2006.03.008

Comprehensive Psychiatry

Volume 48, Issue 1, January–February 2007, Pages 88-94

https://doi.org/10.1016/j.comppsych.2006.03.008 Get rights and content

Abstract

Objective

The study aimed to use the Generalizability Theory to investigate the reliability and precision of the split version of the Global Assessment of Functioning (GAF).

Materials

Six case vignettes were assessed by 2 samples; one by 19 experienced and independent raters and another by 58 experienced raters from 8 different day-treatment units, evaluating both symptom and function scores of GAF.

Methods

Generalizability studies were conducted to disentangle relevant variance components accounting for error variance in GAF scores. Furthermore, decision studies were conducted to estimate the reliability of different measurement designs, as well as precision in terms of error tolerance ratio.

Results

Both symptom and function scores of GAF were found to be highly generalizable, and a measurement design of 2 raters per subject was found to be most efficient with respect to reliability, precision, and use of resources.

Conclusion

Both symptom and function scores of GAF seem highly consistent across experienced raters.

Section snippets

Background

The first standardized and broadly used instrument for assessing patients overall mental health was introduced in 1962 when Luborsky [1] reported the development of the Health-Sickness Rating Scale. Some decades later, Endicott et al [2] modified the original instrument, which resulted in the Global Assessment Scale (GAS). Both the Health-Sickness Rating Scale and GAS are single 100-point rating scales reflecting overall functioning from 1, representing the hypothetically sickest, to 100,

The samples in the study

In this study, 2 samples are analyzed and compared, where both samples scored the symptom and function dimension of GAF on the same set of 6 case vignettes. The first sample consisted of 19 experienced psychiatrists across several mental health regions of Norway, who scored the case vignettes in 1998. In 2001, 8 units from the Norwegian Network of Psychotherapeutic Day Hospitals [13] participated in a study where the same case vignettes were GAF rated by all staff members. From this, 58 staff

Results

The main findings of this study are as follows: both relative and absolute agreement of GAF symptom and function scores were found to be acceptable, even when assuming only a single rater. Both symptom and function scores of GAF were found highly consistent across raters and units. Considering the large GAF scale (100 points), only minor differences between raters were found.

Table 2 shows the estimated variance components of the 2 measurement designs. For both designs, the largest variance was

Discussion

With respect to both relative and absolute interpretations, GAF scores from single independent raters hold acceptable reliability. Furthermore, there seems to be no noticeable systematic difference between the groups of local raters. Thus, GAF scores from different clinical units seem highly interchangeable. As to the reliability of difference scores, we found no support for any differential construct validity of GAF. Although the reliability, given by E_ρ² and Φ, for symptom and function

Acknowledgment

We wish to thank the staff from the day units in the Norwegian Network of Psychotherapeutic Day Hospitals, and the expert raters for their effort in scoring the GAF case vignettes which made this study possible.

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View full text

Generalizability studies of the Global Assessment of Functioning–Split version

Abstract

Objective

Materials

Methods

Results

Conclusion

Section snippets

Background

The samples in the study

Results

Discussion

Acknowledgment

Psychosomatics

Clinicians' judgements of mental health

Arch Gen Psychiatry

The Global Assessment Scale. A procedure for measuring overall severity of psychiatric disturbance

Arch Gen Psychiatry

Diagnostic and statistical manual of mental disorders

Diagnostic and statistical manual of mental disorders

Revising axis V for DSM-IV: a review of measures of social functioning

Am J Psychiatry

Does the Global Assessment of Functioning assess functioning?

J Ment Health Couns

Diagnostic and statistical manual of mental disorders

Inter-rate reliability of global assessment of functioning in a clinical setting

J Child Psychol Psychiatry

Routine evaluation of mental health: reliable information or worthless ‘guesstimates’?

Acta Psychiatr Scand

Evaluering av GAF-skåring som del av Minste Basis Datasett

Tidsskrift for Norsk Psykologforening

Reliability and validity of DSM-IV axis V

Am J Psychiatry