Depression and anxiety disorders are among the most prevalent mental health conditions globally, contributing significantly to the overall burden of disease and disability [1]. According to the World Health Organization, more than 264 million people suffer from depression worldwide, with anxiety disorders affecting an additional 284 million individuals [2]. These disorders frequently present in primary care settings, often manifesting through somatic complaints or non-specific symptoms, leading to underdiagnosis and undertreatment [3].

Early detection of mental health issues in general practice is essential for timely intervention and better prognosis. Primary care physicians (PCPs) are usually the first point of contact for individuals experiencing mental distress. However, due to time constraints, lack of training, and stigma, mental health conditions may go unrecognized in routine consultations [4, 5]. Therefore, standardized screening tools such as the Patient Health Questionnaire-9 (PHQ-9) and the Generalized Anxiety Disorder-7 (GAD-7) have been developed to facilitate the identification of depression and anxiety, respectively [6].

The PHQ-9 is a self-administered tool that aligns with the diagnostic criteria for major depressive disorder outlined in the DSM-5. It has been extensively validated in primary care populations and is valued for its brevity and ease of use [7]. Similarly, the GAD-7 is widely recognized for assessing the severity of generalized anxiety disorder and has demonstrated strong psychometric properties across diverse populations [8, 9].

Despite their widespread adoption, the diagnostic accuracy of these tools can vary depending on the clinical setting, patient population, and cut-off thresholds used [10]. While previous studies have reported favorable sensitivity and specificity for PHQ-9 and GAD-7, limited data exist on their comparative performance within general practice, particularly in low-resource or high-volume clinical environments [11, 12].

This study aims to assess the diagnostic accuracy of PHQ-9 and GAD-7 in detecting depression and anxiety disorders in a general practice setting. By comparing these tools against structured clinical interviews as the reference standard, this research seeks to provide evidence on their utility and reliability for routine mental health screening in primary care.

The study employed a cross-sectional design. Adults aged 18 to 65 years attending the general outpatient department for any non-emergency complaint were consecutively recruited. Patients with known psychiatric illness, those currently on psychiatric medication, or individuals with cognitive impairments that could interfere with assessment were excluded.

Sample Size

A total of 300 participants were included, based on the expected prevalence of depression and anxiety in primary care and the desired precision for estimating sensitivity and specificity.

Screening Tools

Participants were screened using the Patient Health Questionnaire-9 (PHQ-9) for depression and the Generalized Anxiety Disorder-7 (GAD-7) scale for anxiety. Both tools are self-administered and were provided in the local language, validated through translation-back translation methods.

Reference Standard

All participants underwent a structured clinical interview conducted by a trained clinical psychologist using DSM-5 diagnostic criteria. The psychologist was blinded to the results of the PHQ-9 and GAD-7 to avoid assessment bias.

Procedure
After enrollment, participants were asked to complete the PHQ-9 and GAD-7 during their visit. Subsequently, a clinical interview was scheduled within the same week. Data regarding sociodemographic variables, clinical symptoms, and tool scores were recorded using a predesigned proforma.

Statistical Analysis

Data were entered and analyzed using SPSS version 25. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated for both PHQ-9 and GAD-7, using the clinical interview as the reference. Receiver Operating Characteristic (ROC) curves were plotted, and area under the curve (AUC) was calculated to assess diagnostic performance. A p-value < 0.05 was considered statistically significant.

A total of 300 participants were included in the study, with a mean age of 38.2 ± 11.6 years. Among them, 180 (60%) were female and 120 (40%) were male. Table 1 presents the baseline demographic and clinical characteristics of the study population.

Table 1. Demographic Characteristics of Participants (n = 300)

Based on structured clinical interviews using DSM-5 criteria, 114 participants (38%) were diagnosed with depression and 96 (32%) with anxiety disorders. The distribution of positive screening results on PHQ-9 and GAD-7 is provided in Table 2.

Table 2. Screening Outcomes of PHQ-9 and GAD-7

The diagnostic accuracy measures for both tools were computed. PHQ-9 demonstrated a sensitivity of 89.5%, specificity of 78.2%, PPV of 74.2%, and NPV of 91.2% for detecting depression. GAD-7 showed a sensitivity of 84.3%, specificity of 81.7%, PPV of 70.4%, and NPV of 90.8% for detecting anxiety disorders. These values are detailed in Table 3.

Table 3. Diagnostic Accuracy Measures of PHQ-9 and GAD-7

The ROC analysis further confirmed that both tools demonstrated good diagnostic performance, with PHQ-9 slightly outperforming GAD-7 in terms of overall accuracy (Table 3).

These findings indicate that both PHQ-9 and GAD-7 are valuable screening tools for early detection of depression and anxiety in a general practice setting, with strong sensitivity and negative predictive values that support their utility in clinical screening applications.

The present study aimed to evaluate the diagnostic accuracy of PHQ-9 and GAD-7 as mental health screening tools in general practice, focusing on their ability to detect depression and anxiety disorders. The results revealed that both tools demonstrated high sensitivity and negative predictive values, indicating their potential usefulness for early identification of common mental health conditions in primary care.

Our findings align with earlier studies that established the PHQ-9 as a valid and efficient screening instrument for major depressive disorder in primary care settings, with reported sensitivities ranging from 80% to 92% and specificities from 73% to 88% depending on cut-off values used [1], [2]. The sensitivity of PHQ-9 observed in this study (89.5%) is consistent with that of previous research, suggesting it is well-suited for identifying patients with depression in routine practice [3]. Similarly, the GAD-7, originally validated for detecting generalized anxiety disorder, has shown robust performance across various healthcare environments, with sensitivity and specificity often exceeding 80% [4], [5]. The current study supports these findings, with the GAD-7 achieving 84.3% sensitivity and 81.7% specificity.

Both instruments have the added advantage of being self-administered, time-efficient, and easily interpretable, which is particularly relevant in busy primary care settings where physicians may have limited time to assess psychological symptoms comprehensively [6], [7]. Moreover, previous studies have emphasized that routine use of mental health screening tools can enhance detection rates, reduce stigma, and facilitate early referral to mental health services [8], [9].

The higher negative predictive values for both PHQ-9 (91.2%) and GAD-7 (90.8%) observed in this study further reinforce their screening utility. High NPV is essential in primary care, where the goal is often to rule out conditions reliably to avoid unnecessary interventions or referrals [10].

Despite their strengths, some limitations must be considered. The use of structured clinical interviews as the reference standard, though rigorous, may not fully capture fluctuating symptoms of mental illness, especially in individuals with subclinical presentations [11]. Additionally, the study was conducted in a single urban clinic, potentially limiting the generalizability of the findings to rural or underserved populations, where literacy and health-seeking behavior may vary [12], [13].

Another important aspect is the potential cultural variability in symptom reporting. Emotional distress is often expressed through somatic complaints in many populations, which can reduce the sensitivity of standard screening tools if not culturally adapted [14], [15]. Therefore, while PHQ-9 and GAD-7 appear effective, their optimal cut-off points and interpretation may need to be calibrated according to local context and population characteristics.

In summary, our study contributes to the growing body of evidence supporting the use of PHQ-9 and GAD-7 for early detection of depression and anxiety in general practice. Their high diagnostic accuracy, ease of use, and feasibility make them suitable for routine implementation. However, clinicians should remain aware of contextual factors such as literacy, cultural differences, and coexisting medical conditions when interpreting results.

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