ABNORMAL CLOT RETRACTION, ALTERED FIBRIN STRUCTURE, AND NORMAL PLATELET-FUNCTION IN MULTIPLE-MYELOMA

Clot retraction, measured by serum expression, is absent in some cases of multiple myeloma. Decreased clot retraction has been attributed to platelet dysfunction. A new instrument allows simultaneous measuremen t of platelet-mediated force development during clot retraction and of clot elastic modulus. We report 10 patients with immunoglobulin (Ig) G myeloma in whom the abnormalities of fibrin structure were quantitat ively defined and platelet-fibrin interactions were assessed. Fiber ma ss-to-length ratios were calculated from gel turbidity. Platelet force development and clot elastic modula were measured in platelet-rich pl asma gels. Fiber mass-to-length ratios for IgG myeloma patients were s maller (means +/- SE) (0.98 +/- 0.19 x 10(13) Da/cm) than for normal c ontrols (1.36 +/- 0.06 X 10(13) Da/cm), indicating thinner fiber forma tion. Elastic modula of myeloma clots (51,013 +/- 14,660 dyn/cm(2)) we re strikingly larger than modula for normal controls (23,355 +/- 1,887 dyn/cm(2)), indicating that such clots are mechanically less flexible . Platelet force development 1,200 s after thrombin addition was not d iminished in myeloma patients (8,315 +/- 1,155 dyn) vs. controls (6,90 6 +/- 606 dyn). Abnormal clot retraction in myeloma appears to be prim arily due to altered clot structure rather than platelet dysfunction.