A pseudo-random patient sampling method evaluated

Abstract

Objectives: To compare two human immunodeficiency virus (HIV) cohorts to determine whether a pseudo-random sample can represent the entire study population.

Study design and setting: HIV-positive patients receiving care at eight sites in seven Asian countries. The TREAT Asia HIV Observational database (TAHOD) pseudo-randomly selected a patient sample, while TREAT Asia HIV Observational database-Low Intensity Transfer (TAHOD-LITE) included all patients. We compared patient demographics, CD4 count, and HIV viral load testing for each cohort. Risk factors associated with CD4 count response, HIV viral load suppression (<400 copies/mL), and survival were determined for each cohort.

Results: There were 2,318 TAHOD patients and 14,714 TAHOD-LITE patients. Patient demographics, CD4 count, and HIV viral load testing rates were broadly similar between the cohorts. CD4 count response and all-cause mortality were consistent among the cohorts with similar risk factors. HIV viral load response appeared to be superior in TAHOD and many risk factors differed, possibly due to viral load being tested on a subset of patients.

Conclusion: Our study gives the first empirical evidence that analysis of risk factors for completely ascertained end points from our pseudo-randomly selected patient sample may be generalized to our larger, complete population of HIV-positive patients. However, results can significantly vary when analyzing smaller or pseudo-random samples, particularly if some patient data are not completely missing at random, such as viral load results.

Keywords: Asia; Cohort; HIV; Observational data; Patient sampling; Selection bias.

Figure 1. The response to first-line ART, by cohort

(A) Median CD4 cell count change (cells/μL), with interquartile range, from ART initiation across all countries, by cohort. (B) Proportion of patients with HIV viral load <400 copies/mL since ART initiation across all countries, by cohort, where the shaded region represents the 95% binomial proportion confidence interval. (C) Probability of survival, as from Kaplan-Meier estimates, from ART initiation across all countries, by cohort (τ = log rank test).