01 - 1. General principles

1. General principles

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1. General principles Rating scales give clinicians an objective benchmark to support critical treatment decisions. Regular use of rating scales can provide information that aids in diagnosis, prognosis and therapeutic monitoring. Further, when self-report scales are used, an item-by-item analysis can help to identify the exact symptoms that a patient considers most troublesome and challenging so they can be targeted during the consultation process. Rating scales can be used for (1) screening for the presence of a psychiatric condition (2) diagnosis of a psychiatric illness (such scales are often termed diagnostic schedules) (3) estimating severity of various conditions and their response to treatment (4) assess functional capacity and well-being. Rating scales can be either self-rated or observer rated. Some observer-rated scales require clinical experience (clinician-rated) while trained non-clinical personnel can use others. Self-rated Observer rated Beck’s Depression Inventory Zung Depression Inventory Symptoms checklist SCL GHQ Lunser’s (extrapyramidal) Edinburgh postnatal depression scale Dementia scales PANSS BPRS HAMD MADRS YBOCS SCID Scales are based on psychometric properties; aim to measure dimensions of psychopathology (symptoms) often at the present state (the duration of which is defined variously). Schedules are based on clinical expectations; deal with categories of disorders (syndromes) based on known classification systems. A schedule may be devised to focus on either past or present status or both. Two types of procedures are used when selecting items (symptoms) for scales. The first method is based on the previous clinical literature to determine the appropriate items. The second method is based on calibration. In this method, a large number of questions are tested to find the most discriminating items between a ‘known ill’ and a ‘presumed well’ group. The items that are most significant in a statistical sense are chosen to represent the scale that is devised. Considerations for selecting a screening measure for use in a study include  Characteristics of the population to be screened,  Psychometric properties of the instrument,  Time required to complete the measure,  Ease of use, and  Cost of obtaining the measure

© SPMM Course General Health Questionnaire is an all-purpose screening tool that is often used as a first-level assessment instrument in epidemiological studies before detailed diagnostic schedules are employed.  Goldberg introduced the General Health Questionnaire (GHQ)  GHQ was developed as a screening tool to detect those likely to have or be at risk of developing psychiatric disorders  It is available in a variety of versions using 12, 28, 30 or 60 items, the 28-item version is used most widely.  Each item is scored as a 4 point Likert (0-3) allowing a total possible score on the GHQ 28 of 0 to 84.  Using alternative binary scoring method (with least symptomatic items scoring 0 and the most symptomatic items scoring 1), the 28- and 30-item versions classify any score exceeding the threshold value of 4 as achieving ‘psychiatric caseness’. The caseness threshold is 3 for the 12-item version. Psychiatric caseness is a probabilistic term—whereby, if such respondents presented in general practice, they would be likely to receive further attention.  It should be noted that the GHQ is not usually used for predictive purposes.  Reliability coefficients have ranged from 0.78 to 0.95 in various studies.