Potential of an age adjusted D-dimer cut-off value to improve the exclusion of pulmonary embolism in older patients: a retrospective analysis of three large cohorts

Editor, I read the report by Douma et al with a great interest [1].
Duoma et al. concluded that "The age adjusted D-dimer cut-off point,
combined with clinical probability, greatly increased the proportion of
older patients in whom pulmonary embolism could be safely excluded [1]." I
have some questions on this report. Based on the nature of a retrospective
analysis, there are several considerations. First, how can Douma et al.
confirmed on the homogeniticity of the subjects in the three cohorts?.
Second, how can Douma et al. confirm on the QC of the laboratory analysis
in all included cohorts? Do the analyzers in all cohorts share the
complete common diagnostic properties? These questions can be the points
for further discussion.

References

1. Renée A Douma, Grégoire le Gal, Maaike Söhne, Marc Righini, Pieter W
Kamphuisen, Arnaud Perrier, Marieke J H A Kruip, Henri Bounameaux, Harry R
Büller, and Pierre-Marie Roy. Potential of an age adjusted D-dimer cut-off
value to improve the exclusion of pulmonary embolism in older patients: a
retrospective analysis of three large cohorts
BMJ 2010; 340: c1475

Competing interests:
None declared