The QPD Panel screens for 9 mental disorders based on Diagnostic and Statistical Manual of Mental Disorders, fourth edition (DSM-IV)17 diagnostic criteria: major depression, dysthymic disorder, bipolar disorder, generalized anxiety disorder, panic disorder, obsessive-compulsive disorder (OCD), bulimia nervosa, alcohol or substance abuse, and somatization disorder. The report provides numeric scores indicating the severity of symptoms, a specific psychiatric diagnosis, and a list of the symptoms leading to the diagnosis (when applicable). The test also identifies patients who may be at risk for suicide. In the sample report (Figure 1) the depression severity score is outside the normal reference range, indicating clinically significant symptoms, and a note indicates a diagnosis of major depression. The last section of the report lists the specific symptoms reported by the patient that led to this diagnosis.
The QPD Panel has been used in a variety of ways in primary care clinics. In some facilities, all patients are given the QPD Panel when they check in with the receptionist, and they complete the test in the waiting room. The report is then put in the patient’s chart and is available to the physician before examining the patient. In other facilities, physicians administer the QPD Panel at their discretion, when they suspect a psychiatric disorder. In those facilities, physicians ask patients to complete the QPD Panel after conducting an initial examination. While the patient answers the questions the physician goes on to examine other patients, then returns to review the QPD Panel results.
The test begins with the following instructions, displayed on the LCD screen:
Your doctor is interested in both your physical and emotional health. This questionnaire will ask about physical and emotional problems you may be having. Your answers will help your doctor give you the best medical care possible.
You will see a series of statements. If a statement applies to you, press the button labeled True. If a statement does not apply to you, press the button labeled False.
Your answers are confidential, between you and your doctor, so please answer as honestly as you can. Most people finish this questionnaire in 5 to 10 minutes.
The instructions are followed by a series of diagnostic questions. The test incorporates branching and logic, so all patients do not see the same questions. Instead, questions are selected for presentation on the basis of the answers to previous questions. Thus, healthy patients are not asked irrelevant questions, and patients who may have mental disorders are examined in-depth.
Test Design
The test combines features of an inventory and a structured interview. All patients respond to a core set of 59 questions (like an inventory); when responses suggest a possible psychiatric disorder the test branches into modules that probe in-depth (like a structured interview). The test contains more than 200 diagnostic questions, but a patient will see only a subset of them. Scoring is done electronically. Numeric scores reflecting the severity of disorders are created by summing the number of relevant test items (symptoms) endorsed by the patient. The test does not use cut-points to make specific psychiatric diagnoses (ie, categorical diagnoses like major depressive disorder, dysthymic disorder, or OCD). Instead, pattern-matching algorithms match symptoms reported by the patient against DSM-IV diagnostic criteria, and printed notes on the report (not numeric scores) indicate the specific DSM-IV diagnosis. Diagnosis of alcohol or substance abuse is an exception, with positive findings based on a cut-point taken on the alcohol/substance abuse numeric score.
Reliabilities (coefficient a)18 of the numeric severity scores range from .78 to .95, indicating that the scores are relatively free of measurement error. In addition to meeting appropriate psychometric requirements, all items included in the QPD Panel met strict criteria with respect to patient acceptance: (1) the items required no more than a grade school reading level; (2) patients rated the items as clear and easy to understand; (3) patients rated the items as appropriate for primary care (ie, they were not perceived as inappropriate or overly intrusive); and (4) patients could respond to the items without assistance. Overall readability of the test is at grade level 5.0, as assessed by the Flesch-Kincaid Grade Level score, which is based on the average number of syllables per word and words per sentence. The test construction methods have been described in greater detail elsewhere.14
Validity Studies: Overview of Design
We report the results of 3 studies that address the validity of the QPD Panel. The first study examined validity for the psychiatric diagnoses (categorical diagnoses) of major depression, generalized anxiety disorder, panic disorder, and OCD. Diagnoses provided by the Structured Clinical Interview for DSM-IV (SCID),19 widely regarded as a diagnostic gold standard, served as criterion standards. The second study examined the validity of the QPD Panel alcohol/substance abuse scale by evaluating the scale’s ability to differentiate known abusers from healthy control patients. The third study reports convergent validity correlations between selected QPD Panel severity scores and established measures. [Table 1] provides an overview of the 3 studies. Additional information about study methodology is presented in the following section.