(906) Patient Weight, Not Height, Significantly Influences cfDNA Screening Performance

Asses the role of patient weight, versus height and BMI, in influencing the performance of cell-free DNA (cfDNA) screening, with a focus on fetal fraction and the rate of no calls due low fetal fraction.

Study Design:

Retrospective study of 7606 consecutive patient samples submitted for cfDNA screening at one laboratory.  The samples were subjected to DNA extraction, library preparation, and whole-genome massively parallel sequencing, as outlined by Jensen et al. These samples were systematically sorted into BMI groups as per the World Health Organization criteria. Fetal fraction and samples reported as QNS across each BMI category were reviewed.

Results:

A strong inverse relationship between patient weight and fetal fraction across all BMI categories was identified (correlation coefficient -0.993). The highest average fetal fraction (10.6%) was observed in the Underweight category, while the lowest average fetal fraction (6.0%) was noted in the Obesity Class III category. Conversely, patient BMI and height exhibited only a weak relationship across the BMI categories, with a correlation coefficient of -0.44. The average patient height stayed relatively constant across all BMI categories, ranging from a low of 64.3 inches in the Pre-obesity and Obesity Class I categories to a high of 64.9 inches in the Underweight category. The overall QNS rate was 0.41% (n=31) across all BMI categories, with the most frequent occurrence in the Obesity Class III category (1.58%, n=8).

Conclusion:

This analysis highlights that patient weight significantly influences the performance of cfDNA screening, particularly in terms of fetal fraction and the rate of QNS results. While BMI can be used to make similar comparisons, it does so primarily because it includes weight as a variable. These findings highlight the importance of focusing on patient weight when discussing the performance of cfDNA screening.