Investigating predictive value and effect estimates between two commonly used depression scales via secondary data from HPTN 068, a conditional cash transfer trial of adolescent girls and young women in South Africa

<strong><span data-contrast="auto">Intro</span></strong><span data-ccp-props="{}">&nbsp;</span> <span data-contrast="auto">The Child Depression Index (CDI) and Center for Epidemiologic Studies Depression scale (CESD) are scales to measure and screen for depression. CDI is a version of the Beck Depression Inventory simplified for minors, and CESD is generally used for adults. Secondary data from HPTN 068 provided a unique opportunity to assess scale concordance in an adolescent female sample, a time period when minors transition to young adulthood.</span><span data-ccp-props="{}">&nbsp;</span> <strong><span data-contrast="auto">Methods</span></strong><span data-ccp-props="{}">&nbsp;</span> <span data-contrast="auto">Young women (n = 2530) in rural South Africa were randomized 1:1 to a conditional cash transfer (CCT) or control. Participants were eligible to receive the CCT while they remained unmarried and maintained school attendance. Both the CDI and the CESD were administered at final study visit. Without a gold standard, we compared positive predictive values (PPV) of CDI and CESD </span><em><span data-contrast="auto">for each other</span></em><span data-contrast="auto"> across age and intervention assignment and explored how choice of metric impacted CCT effect estimate.</span><span data-ccp-props="{}">&nbsp;</span> <strong><span data-contrast="auto">Results</span></strong><span data-ccp-props="{}">&nbsp;</span> <span data-contrast="auto">At study conclusion, participants had a median age of 18 (IQR: 17,18). The prevalence of depression was 26% via CDI and 27% via CESD. But PPV for CDI in detecting depression via CESD was only 53%, and the PPV of CESD for CDI was 57%. The PPVs were lower for &lt;18 participants and higher for 18+ participants. The PPV of CDI for CESD was 52% for the &lt;18 group and 57% for the 18+ group. The PPV of CESD for CDI was 41% for the &lt;18 group and 62% for the 18+ group. Comparing risk difference estimates, the CCT reduced depression by 0.8 percentage points (95% CI: -4.9, 3.2) via CDI and by 4.1 percentage points (95% CI: 0.0, 8.2) via CESD.</span><span data-ccp-props="{}">&nbsp;</span> <strong><span data-contrast="auto">Conclusion</span></strong><span data-ccp-props="{}">&nbsp;</span> <span data-contrast="auto">The PPV between CDI and CESD are surprisingly low, given the same stated construct and similar prevalence and effect estimates. The PPV of the CESD for CDI is greater than the PPV of CDI for CESD among 18+ participants, and vice versa for &lt;18 participants. These results suggest that CDI and CESD measure different (sets of) constructs with age-based differences in depression symptoms or scale interpretation.</span><span data-ccp-props="{}">&nbsp;</span>