The Outcome Questionnaire-45.2 (OQ-45.2) is purported to measure important areas of functioning (symptoms, interpersonal problems social role functioning and quality of life) that are of central interest in mental health. In recent years research employing the OQ-45.2 has focused on tracking patient change over time and indicating if and when patients return to a normal state of functioning as proposed by criteria for clinically significant change. This study examined the OQ-45.2 cut-off scores for clinical significance by comparing concordance rates with cut-off scores based on other measures of psychotherapy outcome. Instruments of each area of functioning were administered to patients undergoing psychotherapy at the beginning and end of treatment. Each patient's degree of success was then classified by each instrument and differences between the measures were examined. The results provided evidence for the construct validity of the concept of clinical significance and the OQ-45.2 cut-off scores demarking the boundaries for functional/dysfunctional samples. Correspondence between measure estimates for classifying patients as functional or dysfunctional averaged 85%. Estimates of agreement between measures classification of patients as meeting criteria for clinically significant change averaged 65%. Implications of these results were discussed in reference to use of the OQ-45.2 and the concept of clinical significance.
Contemporary research focused on applied clinical questions often relies heavily on using operational definitions of meaningful change at the level of the individual patient. This research includes studies that explore the dose-effect relationship, i.e., the amount of therapy needed for recovery (e.g., Anderson & Lambert, 2001; Maling, Gurtman, & Howard, 1995). In such studies a definition of meaningful change (clinically significant change) allows researchers to estimate the number of sessions needed to meet such an event. In addition, studies aimed at improving the quality of services require operational definitions to judge a particular patient's treatment response and the need for additional services (Kordy, Hannover, & Richard, 2001; Lambert, Hansen & Finch, 2001; Lueger et al, 2001). Finally, the call for presentation of the results of clinical trials research that include estimates of the practical consequences of treatment for individual patients is widespread (e.g., Barlow, 198 1; Hugdahl & Ost, 1981; Kendall, 1999; Saunders, Howard, & Newman, 1988).
The most frequently used method for operationalizing clinical significance for the preceding research activities is that described by Jacobson and Truax (1991). They proposed a two step criteria. The first step entails an evaluation of reliable change by calculating a Reliable Change Index (RCI). As defined by Jacobson and Truax, the RCI is obtained by subtracting a pre-treatment score from a post-treatment score and dividing by the standard error of the measurement (Christensen & Mendoza, 1986 (1); Jacobson, Follette, & Revenstorff, 1984). A particular change is considered to be reliable when it exceeds measurement error at the .05 level of confidence.
The second step consists of defining a cut-off point between functional and dysfunctional samples. This cut-off represents the point at which a person's score is more likely to fall in the distribution of scores characteristic of normal functioning. The use of this social comparison methodology has the advantage of referencing a client's state of functioning against peer functioning rather than demanding that the client be asymptomatic in order to be considered healthy (Kendall & Grove, 1988; Kendall, Marrs-Garcia, Nath, & Sheldrick, 1999). When both the RCI and the normative group comparison criterion are met, the change is regarded as clinically significant according to the Jacobson method.
Despite widespread use of the Jacobson method (Ogles, Lunnen, & Bonesteel, 2001), little research has been conducted on its' validity. …