Screening for somatization and hypochondriasis in primary care and neurological in-patients

Abstract

The aim of this study was to investigate the internal and external validity of the Whiteley Index as a screening instrument for somatization illness. A 14-item version of the Whiteley Index for hypochondriacal traits was given to 99 of 191 consecutive primary care patients, aged 18–65 years, and to 100 consecutive patients, aged 18–60 years, admitted for the first time to a neurological ward. The primary care sample was, in addition, interviewed by means of the SCAN (Schedules for Clinical Assessment in Neuropsychiatry) psychiatric interview. The GPs and the neurologists were asked to rate various characteristics of the patients that might indicate somatization. The internal validity of the Whiteley Index was tested by means of latent structure analysis. On this basis, a reduced seven-item scale (Whiteley-7 scale) and two subscales (i.e., an Illness Conviction and Illness Worrying scale, each with three items) were constructed. All three had a high internal validity fitting into the very restricted Rasch statistical model (p>0.05) and an acceptable transferability between most of the subpopulations investigated. In the primary care population, the Whiteley-7 and the Illness Conviction scales at cut-point 0/1 showed 1.00 and 0.87 sensitivity and 0.65 and 0.87 specificity, respectively, using as “gold standard” the fulfillment of criteria for at least one ICD-10 somatoform disorder, and 0.71 and 0.63 sensitivity and 0.62 and 0.87 specificity, respectively, as gold standard for the fulfillment of criteria for at least one DSM-IV somatoform disorder, excluding the NOS diagnostic group. The Illness Worrying subscale showed less impressive performance in this respect. The agreement between the Whiteley-7 scale including the two subscales and neurologists’ rating and the GPs’ rating and the somatization subscale on the SCL-90 was modest or worse. It may be concluded that the Whiteley-7 scale and the Illness Conviction subscale had acceptable psychometric profiles, and both seem to be promising screening tools for not only hypochondriasis but also for somatoform disorders in general.

Introduction

Somatization illness is highly prevalent in all types of medical settings [1], but often remains unrecognized 2, 3. This lack of recognition might result in unnecessary testing, admission, surgery, medication, and suffering for patients 4, 5. From both research and clinical points of view, a simple, valid screening instrument for somatization illnesses would therefore be of great value, but presently does not exist.

Various questionnaires have been developed to screen for somatization illnesses. The latent factors or dimensions that these questionnaires screen for can be divided roughly into three areas. First, illness behavior, including variables such as number of doctor visits, “doctor shopping,” utilization of health-care resources, disability, etc. Examples of illness behavior include some of the components of the Illness Attitude Scale (IAS) [6]. One of the problems of the illness behavior concept as it is currently used is that it will probably only detect somatizers who have been ill for some time or have become chronic. The second area involves screening for physical symptoms on a predefined list, such as the SCL-90 Somatization subscale [7] or the Somatic Symptom Index (SSI) [8]. Using physical symptoms may be adequate in populations with a low prevalence of genuine physical disorders; however, because of the lack of specificity of the symptoms screened for, this screening concept may be dubious in high-prevalence populations such as general hospital in-patients [9].

The third area is cognitive/emotional; that is, the patient’s beliefs in and fear of illness and attribution of physical sensations to physical illness. An example of this is the Whiteley Index, which has been used widely since the 1960s [10]. This index is a binary self-report questionnaire and, according to Pilowsky and others 10, 11, 12, it can be subdivided into three factors: “disease conviction,” “bodily preoccupation,” and “disease fear or worrying”; consequently, it has been used for measurement of hypochondriacal traits. Its ability to detect somatoform disorders other than hypochondriasis is unknown. The index has been used extensively in its original version as well as in different modified versions, and also as part of the Illness Behavior Questionnaire (IBQ) and the IAS questionnaire 6, 13.

The validity of the different screening instruments has only rarely been tested. Statistical psychometric research has advanced in recent years, and the development of potent methods with regard to the construction and evaluation of screening tests has progressed 14, 15, 16. To a very limited extent, these methods have been used in previous studies.

The aims of the present study were: (1) to investigate the validity of the Whiteley Index as a screening instrument for somatization illness by exploring the psychometric characteristics of the index in two different patient settings; and (2) to attempt to construct a more valid scale on the basis of the results.