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Updated: Aug 7, 2026
Diffuse Reflectance Spectroscopy: Getting the Capillary Refill Test Under One's Thumb
Published on: December 2, 2017
Reflectance spectroscopy of clotting blood: a description of the time-dependent behavior
1Biophysical Laboratory, Edith Nourse Rogers Memorial Veterans Hospital, Research Service, Bedford, Mass 01730, USA. fagreco;caearthlink.net
Context:
Research into whether cyclooxygenase-2 (COX-2) inhibitors affect thrombosis has been hampered by the lack of a specific assay. Erythrocytes modulate the effect of aspirin on platelets, which suggests that tests of whole blood clotting may be more sensitive.
Objectives:
To determine whether reflectance spectroscopy of clotting blood generates useful information about coagulation and whether it shows an effect of COX-2 inhibitors.
Design:
A survey of 14 adults examined the range of phenomena demonstrated by reflectance spectroscopy. These phenomena were compared before and after treatment with a COX-2 inhibitor in 4 subjects.
Setting:
Out-patient clinic.
Main Outcome Measure:
Reflected light intensity was measured from blood as it clotted in a cuvette thermostated at 37 degrees C.
Results:
The survey of healthy adults showed that the time course of reflected light intensity is similar at all wavelengths and may be divided into 4 stages: a monotonic decrease, a sigmoidal increase, a linear region, and a terminal phase. Clot formation as determined by tube inversion occurs at the transition between the first and second phases; the sigmoidal increase cannot be due to fibrin polymerization. The terminal phase coincides with clot retraction. Similar results are obtained in native whole blood and in recalcified citrated blood. Cyclooxygenase-2 inhibitors have an intrinsic effect on the sigmoidal increase ex vivo (P <.001).
Conclusions:
Reflectance spectroscopy generates unique information about clotting blood. It is feasible to use anticoagulated blood to elucidate the events underlying the time course and to investigate the effects of COX-2 inhibitors.
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