Re: Underascertainment of multiple myeloma challenges robustness of third NRPB study of nuclear vete
Your news item described our study of participants in the UK
atmospheric nuclear weapons test programme. Comparisons were made between
a pre-defined cohort of test participants and a matched control group.
Mortality and cancer incidence were ascertained on exactly the same
footing for test participants and controls, using primarily the National
Health Service Central Registers, as is standard for many epidemiological
studies in the UK.
In her response to this news item, Ms Roff suggests that the study is
flawed because of “underascertainment of cases of multiple myeloma”.
She is incorrect. The critical scientific condition that must be met
in a cohort study such as ours is that test participants and controls
should be identified in the same way so that the extent of ascertainment
of cancers in the two groups will be the same. In this way, the design of
the study avoids bias arising through ascertainment of cancers being
greater in the test participant group or in the control group. To
supplement cases in an ad hoc way could introduce bias, and we were
careful to avoid this.
We do not accept Ms Roff’s conclusion or the approach that she has
taken in her response. Details of the status of her cases are in the
report of the study, NRPB-W27, which is available from
http://www.nrpb.org. An independent Advisory Group (Chairman: Professor
Nicholas Wald) oversaw our analysis and was satisfied that the
epidemiological methods we used were sound.
C R Muirhead, G M Kendall
National Radiological Protection Board,
Oxon, OX11 0RQ
Funding for the maintenance of this database and for its analysis has been provided by the Ministry of Defence.
Competing interests: No competing interests