Population Assessment of Tobacco and Health

Missing Data for Biomarkers Tips for Using the PATH Study Data User Forum

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Missing Data for Biomarkers

I am reviewing the urinary nicotine metabolite biomarker data and I am confused about why there are so many missing values. For example, for norcotinine, there are only 8,098 cases out of 11,519. I thought that values below the limit of detection were imputed with LOD/sqrt2, so I am wondering why participants have missing values for the biomarkers that weren't imputed. I haven't been able to find anything in the documentation or the user guide that explains why participants have missing values. Can someone please advise? The reason for missingness is going to determine whether or not we are able to use the data. Thanks!

Missing Data for Biomarkers (reply)

Thanks for asking your question through the forum so we can help PATH Study data users to find the information.

The explanation for this difference appears on pp. 2 and 3 of the Lab Panel Documentation for Urine Panel - Urinary Nicotine Metabolites (Cotinine and Hydroxycotinine) (UNICM).

For samples with cotinine levels above or equal to 20 ng/mL, the “Nicotine Metabolites and Analogs in Urine” method (Centers for Disease Control and Prevention [CDC], Division of Laboratory Sciences [DLS] method 2021, urinary nicotine metabolites) was applied, and nicotine, its six major metabolites (cotinine, trans-3'-hydroxycotinine, nicotine-N-oxide, cotinine-N-oxide, nornicotine, and norcotinine), anatabine and anabasine were measured.

For samples with cotinine levels less than 20 ng/mL, the “Cotinine and Hydroxycotinine in Urine” method (DLS method 2024) was applied to measure only the cotinine and trans-3’-hydroxycotinine levels.


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