Hello George, Good to hear from you. I hope that all is well with you. Greet the folks at Precision the next time you see them. There are a number of questions that would be good to raise. For example, for what clinical situations are the OB docs using FSP ? It cannot, of course, be used for VTE exclusion. They are correct, if the reference interval for the D-dimer is developed from apparently healthy adults (not pregnant), then most pregnant women will have values above that level by the time they reach the second trimester of their pregnancy. Some laboratories have developed RIs for the trimesters of pregnancy, a difficult task to complete within one institution. Use of values that are published could be done if done with care. Ideally the published data would be from the same method being used by the laboratory. In addition, the published data most frequently will not include the type of units measured/reported (DDU/FEU), see Cui JS, Jing ZP, Zhuang SJ, et al. D-dimer as a biomarker for acute aortic dissection: a systematic review and meta-analysis. Medicine (Baltimore). 2015 Jan;94(4):e471. I’m not aware of any publication of trimester-specific thresholds for the exclusion of VTE with sufficient numbers of subjects to be confident in the statistical analysis but there are reports of such thresholds with smaller numbers. Finally, any information provided by the FSP can be derived from the D-dimer if one keeps in mind the natural elevation of the reference interval through the pregnancy. The info from the chapter is attached with a couple of additional references if you would find that helpful. All the best, John.
Here is Dr Olson's book chapter information: /sites/default/files/d-d_preg_olson_9-12-17.pdf