The Addiction Severity Index medical and psychiatric composite scores measure similar domains as the SF-36 in substance-dependent veterans: concurrent and discriminant validity

Abstract

Background: Recently attention has focused on the assessment of functional health status in substance-dependent individuals. The addiction severity index (ASI) is a widely used assessment instrument that includes scales to reflect current medical and psychiatric status. This study examines the concurrent validity of these ASI composite scores in relation to the short form 36-item health survey (SF-36), a well-established measure of health-related quality of life/functional health status. Methods: Veterans (n = 674) were assessed at admission to substance dependence treatment. Correlations were performed between ASI composite scores and SF-36 scales and the physical and mental summary components (PSC and MSC, respectively). Areas under receiver operating characteristic (ROC) curves determined the descriminative ability of the ASI composites to ascertain impairment. Results: The ASI medical composite score demonstrated robust correlations with the four SF-36 scales that relate to physical health and with the PCS. The ASI psychiatric composite score had robust correlations with the four SF-36 scales related to mental health and with the mental component summary (MCS). ROC curves indicated that the ASI medical (AUC = 0.83) and psychiatric composites (AUC = 0.90) accurately detected subjects with impairment. Conclusions: ASI medical and psychiatric composite scores provide effective initial screening for patients with impaired functional status as measured by the corresponding SF-36 component summary scores.

Introduction

Among patients seeking treatment for substance use disorders, increasing attention is being paid to assessment of functional status and quality of life, in addition to measurement of substance use, in evaluating substance dependence severity and treatment outcomes (Daeppen et al., 1998, Garg et al., 1999, Morgan et al., 2003). Patients with substance use disorders exhibit frequent and oftentimes serious medical conditions (Lieber, 1998, Stein, 1999). It is reasonable to presume, and some evidence suggests, that such medical illness affects the course of substance dependence treatment. For example, in an outcome study of 353 opioid-dependent individuals receiving methadone agonist therapy, those with higher levels of medical severity responded more poorly to intensive treatment interventions (Saxon et al., 1996). In another study with a similar sample of opioid-dependent veterans receiving methadone agonist therapy, those with medical needs who got enhanced medical services had improved treatment outcomes (McLellan et al., 1993). Similarly, co-occurring psychopathology is common among individuals with substance dependence (Regier et al., 1990, Kessler et al., 1996) and can affect health-related quality of life (Schaar and Ojehagen, 2003). Interventions directed at the psychopathology also lead to improved treatment outcomes (McLellan et al., 1993, Saxon and Calsyn, 1995). Thus, accurate measurement of the health related quality of life among substance-dependent patients may have treatment implications.

The Addiction Severity Index (ASI), a semi-structured interview that assesses seven domains (medical, employment, alcohol, drugs, family/social, legal, and psychiatric) in which individuals with substance use disorders typically have problems, has gained widespread use as a measure of functional status at both treatment initiation and follow-up (McLellan et al., 1980, Hodgins and el-Guebaly, 1992, McLellan et al., 1992). A composite score for each ASI dimension measures the severity of the problem in that area over the past 30 days. The ASI psychiatric composite appears to have adequate psychometric properties (Alterman et al., 1998). However, the three-item ASI medical composite has been criticized psychometrically (Alterman et al., 1998), and it has not been tested for concurrent validity with well-established measures of health-related quality of life. Thus, concerns about the value of the ASI medical composite raise questions about the utility of ASI subscales for the assessment of health-related quality of life in addiction treatment.

Other assessment options are available though not typically used in substance dependence treatment programs. The Medical Outcomes Study Short Form 36-item health survey (SF-36) has become the most frequently used measure for assessment of health related quality of life in medical conditions (Ware and Sherbourne, 1992, Kazis et al., 1998) and is commonly the basis for computing quality-adjusted life years used in cost-effectiveness analyses. The SF-36 is a self-report instrument that assesses health status over a 4-week-period and measures each of eight health concepts: physical functioning, physical role limitations, bodily pain, social functioning, emotional role limitations, general mental health, vitality, and general health perceptions (Ware and Sherbourne, 1992). The physical component summary (PCS) is an aggregate of the first four health concepts above and the mental component summary (MCS) is an aggregate of the last four concepts. Both the PCS and MCS scales can be compared with standardized population norms.

Several studies have now attempted to apply the SF-36 or the SF-20, its precursor, to various samples of substance-dependent patients. In general these studies show that substance-dependent patients have decrements across most SF-36 scales compared either to patients without substance dependence or to the general population (Ryan and White, 1996, Booth et al., 1998, Stein et al., 1998, Garg et al., 1999, Morgan et al., 2003), although data from the Vietnam Era Twin Registry concluded that decrements among alcohol dependent individuals may be attributable to comorbid conditions and other covariates rather than to alcohol dependence (Romeis et al., 1999).

Few studies have compared ASI and SF-36 results in clinical samples of patients with substance use disorders. A study performed in Switzerland administered the SF-36 and the ASI to 100 alcohol dependent patients and found small to modest correlations in hypothesized relationships, however the sample did not include patients with non-alcohol substance dependence (Daeppen et al., 1998). Compared to scores of the Swiss general population, the SF-36 scores of the alcohol dependent patients were lower on all scales. The report states that SF-36 scale scores were compared to ASI “dimensions” but does not specify if these dimensions were ASI composite scores. In any event, small to modest correlations were found between the ASI medical dimension and all SF-36 scales except emotional role and mental health; the ASI psychiatric dimension had small to modest correlations with SF-36 bodily pain, general health, and vitality and more robust correlations with emotional role and mental health. In a sample of 202 clients from five treatment centers, Butler et al. (2001) found modest correlations between the ASI medical composite and the PCS (based on the abbreviated SF-12) for ASI’s administered by standard interview (−0.34) and the ASI-multimedia version (−0.39). The purpose of the present report is to extend these findings by comparing the SF-36 and the ASI in a larger sample of substance-dependent patients. The sample consisted of treatment seeking veterans with a range of primary substance use disorders. Based on the data of Daeppen et al. (1998), we hypothesized that the combination of ASI medical and psychiatric composite scores would, by virtue of correlating with the corresponding SF-36 scales, serve as an adequate initial screen for impaired physical and mental health related quality of life in substance-dependent patients. Additionally, analogous analyses were performed for sub-samples with primary alcohol, cocaine, and opioid dependence with the hypothesis that the ASI composites would also accurately reflect health related quality of life in individuals with each of these specific disorders.