Incidence rate estimation, periodic testing and the limitations of the mid-point imputation approach. International Journal of Epidemiology, : doi.org/10.1093/ije/dyx134 (2017).

Publication Latest Publications

Title: Incidence rate estimation, periodic testing and the limitations of the mid-point imputation approach
Authors: Vandormael A, Dobra A, Barnighausen T, de Oliveira T, Tanser F.
Journal: International Journal of Epidemiology,:doi.org/10.1093/ije/dyx134 (2017)

Journal Impact Factor (I.F.): 7.738
Number of citations (Google Scholar): 5

Abstract

Background: It is common to use the mid-point between the latest-negative and earliest-positive test dates as the date of the infection event. However, the accuracy of the mid-point method has yet to be systematically quantified for incidence studies once participants start to miss their scheduled test dates.

Methods: We used a simulation-based approach to generate an infectious disease epidemic for an incidence cohort with a high (80-100%), moderate (60-79.9%), low (40-59.9%) and poor (30-39.9%) testing rate. Next, we imputed a mid-point and random-point value between the participant's latest-negative and earliest-positive test dates. We then compared the incidence rate derived from these imputed values with the true incidence rate generated from the simulation model.

Results: The mid-point incidence rate estimates erroneously declined towards the end of the observation period once the testing rate dropped below 80%. This decline was in error of approximately 9%, 27% and 41% for a moderate, low and poor testing rate, respectively. The random-point method did not introduce any systematic bias in the incidence rate estimate, even for testing rates as low as 30%.

Conclusions: The mid-point assumption of the infection date is unjustified and should not be used to calculate the incidence rate once participants start to miss the scheduled test dates. Under these conditions, we show an artefactual decline in the incidence rate towards the end of the observation period. Alternatively, the single random-point method is straightforward to implement and produces estimates very close to the true incidence rate.

Download: Full text paper

Citation: Vandormael A, Dobra A, Barnighausen T, de Oliveira T, Tanser F. Incidence rate estimation, periodic testing and the limitations of the mid-point imputation approach International Journal of Epidemiology,:doi.org/10.1093/ije/dyx134 (2017).


HIV-1 drug resistance before initiation or re-initiation of first-line antiretroviral therapy in low-income and middle-income countries: a systematic review and meta-regression analysis
Journal: Lancet Infectious Diseases (2017)

Universal test and treat and the HIV epidemic in rural South Africa: a phase 4, open-label, community cluster randomised trial
Journal: Lancet HIV (2017)

Longitudinal trends in the prevalence of detectable HIV viremia: Population-based evidence from rural KwaZulu-Natal, South Africa
Journal: Clin Infect Dis. (2017)
All publications...


Page design updated by Tulio de Oliveira, 2013