Introduction: Global Assessment of Functioning (GAF) is an assessment instrument that is known worldwide. It is widely used for rating the severity of illness. Results from evaluations in psychiatry should characterize the patients. Rating of GAF is based on collected information. The aim of the study is to identify the factors involved in collecting information that is relevant for rating GAF, and gaps in knowledge where it is likely that further development would play a role for improved scoring.
Methods: A literature search was conducted with a combination of thorough hand search and search in the bibliographic databases PubMed, PsycINFO, Google Scholar, and Campbell Collaboration Library of Systematic Reviews.
Results: Collection of information for rating GAF depends on two fundamental factors: the sources of information and the methods for information collection. Sources of information are patients, informants, health personnel, medical records, letters of referral and police records about violence and substance abuse. Methods for information collection include the many different types of interview – unstructured, semi-structured, structured, interviews for Axis I and II disorders, semistructured interviews for rating GAF, and interviews of informants – as well as instruments for rating symptoms and functioning, and observation. The different sources of information, and methods for collection, frequently result in inconsistencies in the information collected. The variation in collected information, and lack of a generally accepted algorithm for combining collected information, is likely to be important for rated GAF values, but there is a fundamental lack of knowledge about the degree of importance.
Conclusions: Research to improve GAF has not reached a high level. Rated GAF values are likely to be influenced by both the sources of information used and the methods employed for information collection, but the lack of research-based information about these influences is fundamental. Further development of GAF is feasible and proposals for this are presented.
Keywords: Collecting information, GAF, Global Assessment of Functioning, methodology, psychiatry, rating, severity of illness.