Patient Health Questionnaire Somatic Symptom Severity Scale (PHQ-15)

In the mid-1990s the Patient Health Questionnaire (PHQ), was developed and validated as a shorter self-administered version of the Primary Care Evaluation of Mental Disorders (PRIME-MD). The PHQ was developed by Robert Spitzer, Janet Williams and Kurt Kroenke and colleagues at Columbia University. A large study found the PHQ had diagnostic validity comparable to the original clinician-administered PRIME-MD and was more efficient in clinical practice (Spitzer et al., 1999). The Patient Health Questionnaire Somatic Symptom Severity Scale (PHQ-15) is a brief, self-administered questionnaire that was derived from the full PHQ and is increasingly used to assess somatic symptom severity and screen for the potential presence of somatisation and somatoform disorders (based on DSM-IV criteria) in adults (Kroenke et al., 2002). The scale consists of 15 items that ask whether somatic symptoms, such as stomach pain or dizziness are present within the last 4 weeks and the severity (response categories of “not bothered at all”, “bothered a little” and “bothered a lot”). The PHQ-15 scores of 5, 10, and 15 represent cut off points for low, medium, and high somatic symptom severity, respectively (Spritzer et al., 1994).

Psychometric Properties

The PHQ-15 has been validated in different clinical and occupational populations. (De Vroege et al., 2012; Kroenke et al., 2010). With a cut off score of 6 or more the sensitivity of the PHQ-15 was 78% (true positive) and specificity was 71% (false negative). The negative predictive value of 97% indicates that only 3% of individuals who have a score of less than 6 will have a somatoform disorder (Van Ravesteijn et al., 2009). Convergent validity with the Beck Depression Inventory (BDI) and the General Health Questionnaire-12 (GHQ-12) were positive. Increasing scores on the PHQ-15 are strongly associated with increased functional impairment, disability, health care use and symptom-related difficulty (Changsu et al., 2009; Kroenke et al., 2002).  The PHQ-15 demonstrates acceptable internal consistency (Cronbach coefficient alpha of .80) (Kroenke et al., 2002; Van Ravesteijn et al., 2009; Kroenke et al., 1998). The PHQ-15 has moderate test-retest reliability (intraclass correlation coefficient of 0.83) with a 2 week interval (Van Ravesteijn et al., 2009).

The reliability and validity of the PHQ-15 is unaffected by pertinent individual difference factors such as age, gender and education (Kroenke et al., 2010; Kocalevent et al., 2013; Changsu et al., 2009; Shih-Cheng et al., 2016). The PHQ-15 has been translated into over 20 languages (Spritzer et al., 1994). The scale has been validated in Korean and Chinese populations, however does not perform well in Hispanic populations which could be due to multiple factors within the cultural context that may affect how individuals identify and classify bodily sensations, perceive illness and seek medical attention (APA, 2013; Interian et al., 2006; Changsu et al., 2009; Shih-Cheng et al., 2016). East Asian populations often complain of somatic symptoms rather than reveal any depressive feelings, which is important for clinical practice as somatoform disorders have considerable comorbidity with anxiety and depressive disorders which the PHQ-15 does not screen for (Changsu et al., 2009).

Clinical utility

Overall, the PHQ-15 is a valid and reliable screening tool for presence of somatic symptoms and severity. The DSM-IV main criteria for somatoform disorder was medically unexplained symptoms, whereas, the DSM-5 emphasises distress (APA, 2013). Therefore, the PHQ-15 can be aligned with the DSM-5 criteria as the scale is a screening tool of severity and distress (Shih-Chen et al., 2016). More research is needed to support the PHQ-15 as a measure of responsiveness to changes throughout treatment of individuals with somatoform disorders (Kroenke et al., 2010). It is important to note the PHQ-15 is a self-report scale therefore susceptible to reporting biases. Elevated neuroticism or negative affectivity may lead to inflated symptom reporting (Watson et al., 1989). The main strengths of the scale are it is easy to use (for clinician and client), free and has been validated in different clinical and occupational populations. It has shown good sensitivity and specificity for screening for somatoform disorders, however it is not a diagnostic tool rather an indication of an individual at risk (Kroenke et al., 2010). Further, the scale addresses current rather than previous symptoms to gain more valid and reliable data (Kroenke et al., 2010).

Link to free version of PHQ-15

http://www.phqscreeners.com/sites/g/files/g10016261/f/201412/English_0.pdf
References