Concurrent validation of the Clinical Opiate Withdrawal Scale (COWS) and single-item indices against the Clinical Institute Narcotic Assessment (CINA) opioid withdrawal instrument

Abstract

Introduction

The Clinical Opiate Withdrawal Scale (COWS) is an 11-item clinician-administered scale assessing opioid withdrawal. Though commonly used in clinical practice, it has not been systematically validated. The present study validated the COWS in comparison to the validated Clinical Institute Narcotic Assessment (CINA) scale.

Method

Opioid-dependent volunteers were enrolled in a residential trial and stabilized on morphine 30 mg given subcutaneously four times daily. Subjects then underwent double-blind, randomized challenges of intramuscularly administered placebo and naloxone (0.4 mg) on separate days, during which the COWS, CINA, and visual analog scale (VAS) assessments were concurrently obtained. Subjects completing both challenges were included (N = 46). Correlations between mean peak COWS and CINA scores as well as self-report VAS questions were calculated.

Results

Mean peak COWS and CINA scores of 7.6 and 24.4, respectively, occurred on average 30 min post-injection of naloxone. Mean COWS and CINA scores 30 min after placebo injection were 1.3 and 18.9, respectively. The Pearson's correlation coefficient for peak COWS and CINA scores during the naloxone challenge session was 0.85 (p < 0.001). Peak COWS scores also correlated well with peak VAS self-report scores of bad drug effect (r = 0.57, p < 0.001) and feeling sick (r = 0.57, p < 0.001), providing additional evidence of concurrent validity. Placebo was not associated with any significant elevation of COWS, CINA, or VAS scores, indicating discriminant validity. Cronbach's alpha for the COWS was 0.78, indicating good internal consistency (reliability).

Discussion

COWS, CINA, and certain VAS items are all valid measurement tools for acute opiate withdrawal.

Introduction

The opiate withdrawal syndrome, a constellation of characteristic signs and symptoms, has been called “one of the most stereotyped syndromes in clinical medicine” (Isbell, 1950). The first instrument to quantitatively measure withdrawal was developed by Kolb and Himmelsbach in the mid-1930s (Kolb and Himmelsbach, 1938). That scale was based on clinical observations and was weighted heavily towards physical signs of withdrawal, such as systolic blood pressure changes, mydriasis, fever, and respiratory rate changes. In the 1960s, the Opiate Withdrawal Experience Scale, a subset of self-report questions from the Addiction Research Center Inventory (ARCI), was used to quantify the subjective symptoms of withdrawal (Haertzen and Meketon, 1968). However, this scale was time consuming for subjects to complete, even with the derived short form Opiate Withdrawal Questionnaire (Haertzen et al., 1970).

Following development of those initial instruments, multiple other subjective and objective scales have been developed and used (Handelsman et al., 1987, Judson et al., 1980, Wang et al., 1974, Bradley et al., 1987, Gossop, 1990). Methods for using these scales have sought to improve on sensitivity and specificity for detecting withdrawal by controlling the level of physical dependence, the time point within the withdrawal syndrome when the assessment is made, and the possibility of feigned responses. In 1988, Peachey and Lei reported on the reliability and validity of the Clinical Institute Narcotic Assessment (CINA), one of the first scales to include both opiate withdrawal signs and symptoms (Peachey and Lei, 1988). This scale was validated using a naloxone challenge in heroin-dependent subjects and the peak score was found to predict the clinically determined maintenance methadone dose used to treat these patients. However, the CINA required nursing support to measure heart rate and blood pressure and contained items which could be easily feigned. As well, there was no fixed upper limit to the scale given the variable contribution of blood pressure and pulse ratings.

Wesson and colleagues, therefore, developed the Clinical Opiate Withdrawal Scale (COWS). This scale was designed to be administered quickly, was intended to improve upon existing measurement tools, and was first published in a training manual for buprenorphine treatment (Wesson et al., 1999). The COWS consisted of an 11-item rating system that could be completed within 2 min by a trained observer and could track opioid withdrawal as differentiated from opioid toxicity through serial measurements. Total scores ranged from 0 to 47, and withdrawal was classified as mild (5–12), moderate (13–24), moderately severe (25–36), or severe (>36). These category scores were not derived using standard statistical techniques but were based upon the authors’ clinical expertise (Wesson and Ling, 2003). Because of its clinical utility, its association with buprenorphine maintenance, and ease of application, the COWS has become widely used for assessing opiate withdrawal (Center for Substance Abuse Treatment, 2004). Although the scale was modeled after items on previously validated scales, the COWS itself has never been systematically validated (Wesson and Ling, 2003). The present project assessed the validity of the COWS in comparison to a previously validated instrument, the CINA, using a double-blind, placebo-controlled naloxone challenge in opioid-dependent individuals. As well, comparisons between the COWS, CINA, and single-item subjective ratings (Visual Analogue Scales) were done to examine the validity and possible utility of using one overall item to assess opioid withdrawal.