Biases incurred from nonrandom repeat testing of haemoglobin levels in blood donors: Selective testing and its implications

Ryan K. Chung*, Angela M. Wood, Michael J. Sweeting

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)


To help prevent anaemia, it is a requisite for blood donors to undergo a haemoglobin test to ensure levels are not too low before donation. It is therefore important to have an accurate testing device and strategy to ensure donors are not being inappropriately bled. A recent study in blood donors used a selective testing strategy where if a donor's haemoglobin level is below the level required for donation, then another reading is taken and if this occurs again, a third and final reading is used. This strategy can reduce the average number of readings required per donor compared to taking three measurements for all donors. However, the final decision-making measurement will on average be higher than a single measurement. In this paper, a selective testing strategy is compared against other strategies. Individual-level biases are derived for the selective strategy and are shown to depend on how close a donor's true haemoglobin level is to the donation threshold and the magnitude of error in the testing device. A simulation study was conducted using the distribution of haemoglobin levels from a large donor population to investigate the effects different strategies have on population performance. We consider scenarios based on varying the measurement device bias and error, including differential biases that depend on the underlying haemoglobin level. Discriminatory performance is shown to be affected when using the selective testing strategies, especially when measurement error is large and when differential bias is present in the device. We recommend that the average of a number of readings should be used in preference to selective testing strategies if multiple measurements are available.

Original languageEnglish
Pages (from-to)454-466
Number of pages13
JournalBiometrical Journal
Issue number2
Publication statusPublished - Mar 2019
Externally publishedYes

Bibliographical note

Funding Information:
We gratefully acknowledge the participation of all COMPARE volunteers. We thank the COMPARE study co-ordination teams at the University of Cambridge and at NHS Blood and Transplant (NHSBT), including the blood donation staff at the 10 mobile centres, for their help with COMPARE participant recruitment and study fieldwork. The COMPARE academic coordinating center receives core support from the UK Medical Research Council (MR/L003120/1), British Heart Foundation (RG/13/13/30194), and the UK National Institute for Health Research Cambridge Biomedical Research Centre. The COMPARE study is funded by NHSBT and the NIHR Cambridge Biomedical Research Centre and has been supported by the NIHR-BTRU in Donor Health and Genomics (NIHR BTRU-2014-10024) at the University of Cambridge in partnership with NHSBT.

Funding Information:
Medical Research Council, Grant/Award Number: MR/L003120/1; British Heart Foundation, Grant/Award Number: RG/13/13/30194; National Institute for Health Research, Grant/Award Number: NIHR BTRU-2014-10024

Publisher Copyright:
© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim


  • blood donation
  • diagnostic performance
  • multiple measurements
  • selective testing
  • simulation study


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