This finished IHP 330 Module 7 paper evaluates PHQ-2 depression screening at cutoffs of 2 and 3 and in combination with the PHQ-9, with 2 by 2 tables, sensitivity, specificity, predictive values at 8 and 20 percent prevalence, workload and a recommendation. Searches like "ihp 330 module 7 assignment", "ihp330 module 7 screening test evaluation paper" and "ihp 330 module 7 example" land here.
The IHP 330 Module 7 example, in full
Two, Three or Two Steps? Choosing a PHQ-2 Screening Strategy for Depression in a Primary Care Network
[Student Name]
Southern New Hampshire University
IHP 330: Principles of Epidemiology
Module Seven Assignment
[Instructor Name]
[Date]
The organization, setting and figures below are a composite written as a model document. No real employer, client, colleague or patient is described.
Two, Three or Two Steps? Choosing a PHQ-2 Screening Strategy for Depression in a Primary Care Network
The Program Decision
A composite primary care network screens about 5,000 adults a year for depression at annual visits, as recommended for adults by the national preventive services task force (US Preventive Services Task Force [USPSTF], 2023). Patients complete the two-question PHQ-2. Anyone who screens positive is supposed to complete the nine-question PHQ-9 and be assessed by a clinician, and those with depression are referred to one of two behavioral health care managers. The care managers report that they cannot keep up with the volume of positive screens. The network must decide whether to use a PHQ-2 cutoff of 2 or 3, or a two-step strategy in which only patients with a PHQ-2 of 2 or more complete the PHQ-9, with 10 or more counted as positive.
The Measures
Sensitivity is the proportion of people with the condition who screen positive. Specificity is the proportion without the condition who screen negative. Positive predictive value is the proportion of positive screens that are true cases, and negative predictive value is the proportion of negative screens that are truly free of the condition (Centers for Disease Control and Prevention [CDC], 2012). Sensitivity and specificity describe the test; predictive values describe what a result means for the people being screened and depend on prevalence.
Published Accuracy
A large individual participant data meta-analysis of 100 studies and more than 44,000 participants compared PHQ scores with diagnostic interviews. Against semistructured interviews, a PHQ-2 cutoff of 2 or more had a sensitivity of 0.91 and specificity of 0.67; a cutoff of 3 or more had a sensitivity of 0.72 and specificity of 0.85. The two-step strategy, PHQ-2 of 2 or more followed by PHQ-9 of 10 or more, had a sensitivity of 0.82 and specificity of 0.87, and reduced the number of people who needed to complete the full PHQ-9 by 57 percent (Levis et al., 2020). These figures are used below.
Results at 8 Percent Prevalence
Assuming 8 percent of the network's 5,000 screened adults have major depression, 400 have the condition and 4,600 do not. The table shows the expected results for each strategy.
Table 1
Expected Screening Results for 5,000 Adults at 8 Percent Prevalence
| Strategy | True positives | False negatives | False positives | True negatives | Total positives | PPV | NPV |
|---|---|---|---|---|---|---|---|
| PHQ-2 of 2 or more | 364 | 36 | 1,518 | 3,082 | 1,882 | 19.3% | 98.8% |
| PHQ-2 of 3 or more | 288 | 112 | 690 | 3,910 | 978 | 29.4% | 97.2% |
| PHQ-2 then PHQ-9 | 328 | 72 | 598 | 4,002 | 926 | 35.4% | 98.2% |
Note. True positives = sensitivity x 400; false positives = (1 - specificity) x 4,600. PPV = true positives / total positives; NPV = true negatives / (true negatives + false negatives).
Reading the Results
The cutoff of 2 finds the most cases, missing only 36, but produces 1,882 positive screens, of which only about one in five is a true case. The cutoff of 3 halves the positives but misses 112 people with depression, three times as many. The two-step strategy produces the fewest positives, 926, and the highest positive predictive value, while missing half as many people as the cutoff of 3. Negative predictive values are high for all strategies, because most people screened do not have depression, so a negative screen is reassuring in every case.
The Effect of Prevalence
At a clinic where 20 percent of adults screened have depression, such as a practice serving many patients with chronic pain or recent losses, the same strategies give very different predictive values. For 5,000 adults with 1,000 cases, the positive predictive value rises to 40.8 percent for a cutoff of 2, 54.5 percent for a cutoff of 3 and 61.2 percent for the two-step strategy. Negative predictive value falls, to 92.4 percent for the cutoff of 3, because 280 people with depression would screen negative. Accuracy is a property of the questionnaire, but predictive value belongs to the questionnaire and the clinic together. This is why a single cutoff may not suit every clinic in a network.
The Cost of a False Positive and a False Negative
The two kinds of error carry different costs, and a program decision should weigh them explicitly. A false positive in depression screening leads to a PHQ-9 and a short clinical conversation that usually resolves the question; the cost is staff time and some patient inconvenience, but little harm. A false negative is more serious: a person with untreated depression may lose months of functioning, suffer at work and at home, and in the worst cases face risk to life. Those costs argue for favoring sensitivity. But sensitivity is only valuable if positives are followed up. If care managers are overwhelmed, positive screens sit unaddressed, and a highly sensitive strategy produces a list of people who are identified but not helped. The two-step strategy reflects this balance: it accepts a modest loss of sensitivity to make follow-up of every positive realistic, which is where the benefit of screening actually occurs.
Recommendation
The network should adopt the two-step strategy. It keeps sensitivity close to that of the full PHQ-9, misses far fewer people than a PHQ-2 cutoff of 3, and roughly halves the positives compared with a cutoff of 2, bringing the follow-up workload closer to what two care managers can handle. Because 72 of 400 people with depression would still screen negative, clinicians should be reminded that a negative screen does not override clinical concern, and patients with symptoms should be assessed regardless of their score. The network should track the number of positive screens, the proportion confirmed as depression and the time from positive screen to first care manager contact, and should revisit the choice if a clinic's prevalence differs substantially from the network average.
Limitations
The accuracy figures come from research settings and may differ in routine care, where questions are sometimes read aloud hurriedly or completed by family members. The prevalence of 8 percent is an assumption; the network should estimate its own. The analysis also counts only major depression and does not address suicide risk, which requires separate screening questions and procedures.
Conclusion
Comparing three PHQ-2 strategies through 2 by 2 tables shows the trade-off between sensitivity and workload. The two-step PHQ-2 and PHQ-9 approach offers the best balance for this network, with a positive predictive value of 35 percent at 8 percent prevalence and far fewer positives than a low cutoff. Recalculating at a higher prevalence shows why screening decisions must consider the population as well as the test.
References
Centers for Disease Control and Prevention. (2012). Principles of epidemiology in public health practice: An introduction to applied epidemiology and biostatistics (3rd ed.). U.S. Department of Health and Human Services.
Levis, B., Sun, Y., He, C., Wu, Y., Krishnan, A., Bhandari, P. M., Neupane, D., Imran, M., Brehaut, E., Negeri, Z., Fischer, F. H., Benedetti, A., Thombs, B. D., & Depression Screening Data (DEPRESSD) PHQ Collaboration. (2020). Accuracy of the PHQ-2 alone and in combination with the PHQ-9 for screening to detect major depression: Systematic review and meta-analysis. JAMA, 323(22), 2290-2300. https://doi.org/10.1001/jama.2020.6504
US Preventive Services Task Force. (2023). Screening for depression and suicide risk in adults: US Preventive Services Task Force recommendation statement. JAMA, 329(23), 2057-2067. https://doi.org/10.1001/jama.2023.9297
How this IHP 330 Module 7 example is structured
A screening paper should connect test accuracy to a real decision, so this one begins with the network's problem. It then defines the four measures and presents the published accuracy of each option. The central section builds 2 by 2 tables for a population of 5,000 and calculates predictive values. A second analysis repeats the calculation at a higher prevalence to show how predictive value changes. The recommendation weighs missed cases against follow-up workload.
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IHP 330 Module 7 questions, answered
What does IHP 330 Module 7 usually ask?
Screening modules in epidemiology courses typically ask students to calculate sensitivity, specificity and positive and negative predictive values from a 2 by 2 table and to explain how prevalence affects predictive values, often in the context of a decision about a screening program.
What is the difference between sensitivity and positive predictive value?
Sensitivity is the proportion of people with the condition who test positive; it describes the test. Positive predictive value is the proportion of people who test positive who actually have the condition; it depends on both the test and how common the condition is in the group being screened.
Why does predictive value change with prevalence?
When a condition is rare, most people screened do not have it, so even a small false positive rate produces many false positives compared with true positives, lowering positive predictive value. When the condition is common, true positives make up a larger share of positives, raising positive predictive value.