Erratum: Variability of urinary concentrations of polycyclic aromatic hydrocarbon metabolite in general population and comparison of spot, first-morning, and 24-h void sampling

Correction to: Journal of Exposure Science and Environmental Epidemiology (2010) 20, 526–535; doi:10.1038/jes.2009.41

Tables 2 and 3 contained transcription errors that gave rise to minor errors in the calculated sample-size results. The corrected tables are reproduced below in their entirety and the values presented correctly. The author regrets the error.

Table 2 Variance apportionment for creatinine-adjusted concentrations of 4 PAH metabolites in urine samples from eight subjects over a period of 7 days.

Table 3 Estimated number of samples needed to detect a difference of 10%, 25%, 50%, and 100% in the 1-hydroxypyrene geometric mean concentration with a statistical power of 80% (P<0.05), for single and repeated sampling for spot, first-morning, and 24-hour void sampling.

Additional corrections are described below.

Abstract: The tenth sentence in the abstract should have read: “Intraclass correlation coefficients of 1-PYR levels were 0.55 for spot urine samples, 0.65 [not 0.60] for first-morning voids, and 0.77 [not 0.76] for 24-h voids, indicating a high degree of correlation between urine measurements collected from the same subject over time”.

Statistical Analysis: In the third paragraph, eighth sentence (beginning “The percentage differences”), “controls vs cases” should have been “controls vs exposed group”.

In the last sentence of that section, “(one-tailed)” was omitted from the definition of the next to last term; it should have read “Z_y=yth percentile of a standard Gaussian distribution (one-tailed)”.

Sample Size Recommendation: The fifth sentence in the first paragraph should have read: “The ICCs for 1-PYR in our study were 0.55, 0.65 [not 0.60], and 0.77 [not 0.76], for spot samples, first-morning-voids, and 24-h voids, respectively, indicating considerable agreement between repeated measurements”. The third sentence in the second paragraph should have read “For example, taking an additional sample per person reduces the sample size by 23%, 17% [not 20%], and 12% [not 13%] for spot samples, first-morning, and 24-h voids, respectively”.