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Randomized Controlled Trial
. 2017 Mar;57(3pt2):823-831.
doi: 10.1111/trf.13939. Epub 2016 Dec 1.

A comparison of methods for estimating the incidence of human immunodeficiency virus infection in repeat blood donors

Donald J Brambilla  1 , Michael P Busch  2 , Roger Y Dodd  3 , Simone A Glynn  4 , Steven H Kleinman  5 ; National Heart, Lung, and Blood InstituteRecipient Epidemiology and Donor Evaluation Study-III (REDS-III)
Affiliations
Randomized Controlled Trial

A comparison of methods for estimating the incidence of human immunodeficiency virus infection in repeat blood donors

Donald J Brambilla et al. Transfusion. 2017 Mar.

Abstract

Background: The incidence of human immunodeficiency virus (HIV) in repeat blood donors has been estimated using seven methods. Although incidence is always calculated as cases per person-time, approaches to selecting cases and calculating person-time vary. Incidence estimates have not been compared among methods.

Study design and methods: The seven methods were compared in a simulation study. Because three methods used information from donations made before an estimation interval, 8 years of donation and infection history were simulated, and Years 7 and 8 were treated as the estimation interval for all methods. An exponential random variate was assigned to each donor to simulate the time to infection. Infection risk was constant over 8 years in one scenario but increased at various rates in seven other scenarios. The infection risk scenarios were combined with four mixes of donation frequency to generate 32 test conditions.

Results: Three methods produced biased estimates under all conditions. Three other methods were biased under most conditions. Bias from most methods increased as donation frequency declined. The single method that consistently produced unbiased estimates was the only method that involved the standard epidemiological approach of tabulating all interdonation intervals (IDIs) within the estimation interval. Bias was eliminated from one of the consistently biased methods by a simple modification that involved the average IDI in a sample of donors.

Conclusion: The standard epidemiological approach is recommended if required data are available. Otherwise, the modified method involving the estimated average IDI should be considered. Investigators should use caution when comparing incidence estimates among studies that use different estimation methods or donation frequencies.

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Conflict of interest statement

The authors declare that they have no conflicts of interest relevant to the manuscript submitted to TRANSFUSION

Figures

Figure 1
Figure 1
Hypothetical donation patterns to illustrate differences among estimation methods in the donors and follow-up time included in incidence estimates. Solid line segments indicate follow-up time that is included in an estimate. Dashed line segments indicate follow-up time that is not included. Open symbols indicate uninfected donations, while solid symbols indicate infected donations. Vertical arrows indicate time of infection assumed in the incidence rate calculations for cases that are included in the estimates. An infected donor is included in the numerator of an incidence estimate only if at least part of the follow-up time for that donor is included in the denominator (e.g. donor 5 methods 1,2 vs donor 5 methods 3,4).
Figure 2
Figure 2
Mean estimated incidence with 95% confidence limits. Each set of four symbols represents mean incidence from one estimation method under the four donation frequencies defined in Table 2. The highest average donation frequency is on the left and the lowest on the right in each group of four.
Figure 2
Figure 2
Mean estimated incidence with 95% confidence limits. Each set of four symbols represents mean incidence from one estimation method under the four donation frequencies defined in Table 2. The highest average donation frequency is on the left and the lowest on the right in each group of four.
See this image and copyright information in PMC

References

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