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Relative‐risk‐estimate bias and loss of power in the mantel test for trend resulting from the use of magnetic‐field point‐in‐time (“spot”) measurements in epidemiological studies based on an ordinal exposure scale
Author(s) -
Delpizzo Vincent,
Salzberg Michael R.
Publication year - 1992
Publication title -
bioelectromagnetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.435
H-Index - 81
eISSN - 1521-186X
pISSN - 0197-8462
DOI - 10.1002/bem.2250130504
Subject(s) - statistics , statistical power , field (mathematics) , time point , environmental science , mathematics , physics , pure mathematics , acoustics
We assessed the merits of various point‐in‐time (“spot”) measurement protocols in case‐control studies based on an ordinal exposure scale. After classifying a number of houses on the basis of prolonged monitoring of the ambient, extremely low frequency (ELF) magnetic field, we determined the probability of misclassification for each “spot” measurement protocol. We calculated the effect of this misclassification on the relative risk estimates and on the Mantel test for trend. We found that classification based on a small group of point‐in‐time measurements allows an adequate estimate of the relative risk, although the statistical significance of the dose‐response gradient may be seriously underestimated. However, the use of automated ambient‐field monitors, which results in loss of information on spatial variability, can lead to similar consequences. Therefore, manually collected point‐in‐time measurements remain a viable option for exposure assessment. 1992 Wiley‐Liss, Inc.