Novel and diagnostically applicable information from optical waveform analysis of blood coagulation in disseminated intravascular coagulation C OLIN D OWNEY,R ASHID K AZMI AND C HENG H OCK T OH Department of Haematology, Royal Liverpool University Hospital, Liverpool Received 27 November 1996; accepted for publication 19 March 1997 Summary. Transmittance waveform is the term applied to the optical profile generated from the process of clot formation on standard coagulation tests run on the MDA- 180, a new-generation automated coagulation analyser. In patients with disseminated intravascular coagulation, a characteristically abnormal ‘biphasic change’ is seen on both the activated partial thromboplastin time and thrombin time waveforms. Increasing steepness of the initial slope on the waveform correlates with clinical deterioration and fulmi- nant progression. Although the mechanism underlying the biphasic appearance remains to be elucidated, its identifica- tion provides the diagnostic laboratory with a simple, rapid and robust assay for disseminated intravascular coagulation that can help the clinician with urgent and appropriate therapeutic interventions. Keywords: disseminated intravascular coagulation, optical profile, coagulation assays, automation. In view of the pressures of increasing service demands and the need to improve turnaround time of results, automated coagulation analysers have been increasingly relied upon in general hospital laboratories. In addition to their consider- able impact on workload handling, the new generation of automated analysers can also produce a wealth of new information. Some of this needs to be closely assessed in the hope that it can enable an improved understanding of the in vivo mechanisms of haemostasis and thrombosis as an extension to the limited knowledge currently available from in vitro clotting tests. One new feature which is present on the MDA-180 analyser is the optical profile generated on standard coagulation assays, charting changes in light transmittance over the process and time of clot formation. This is referred to as transmittance waveforms (TW). The normal waveform pattern derived from the prothrombin time (PT) or activated partial thromboplastin time (APTT) can change with in vitro variations in the concentrations of individual blood components (coagulation factor deficiency) (Givens et al, 1996). However, its profile in an in vivo clinical- pathological setting is not known, and as there can be a dynamic balance between pro- and anti-coagulant forces in conditions such as disseminated intravascular coagulation (DIC), we speculated that waveform analysis could provide information that is both novel and, possibly, of adjuvant usefulness in this difficult clinical group. The aim of this study was also to (1) judge the practical applicability of any new information from TW analysis within a busy diagnostic laboratory in comparison to the tests currently employed in diagnosing and monitoring DIC, and (2) establish the specificity of any TW change in DIC. PATIENTS AND METHODS Patients. Specimens were obtained from all in-patients on the Intensive Care Unit (ICU) over a 4-week period (n ¼ 34) and compared with healthy controls (n ¼ 20), patients with haemophilia A (n ¼ 3), haemophilia A with inhibitors to factor VIII (n ¼ 3), haemophilia B (n ¼ 3), factor V deficiency (n ¼ 1), lupus anticoagulant (n ¼ 3) as well as patients on intravenous unfractionated heparin (n ¼ 3), subcutaneous prophylactic unfractionated heparin (n ¼ 3) and warfarin (n ¼ 3). The in-patient samples analysed were those collected by direct venepuncture for ‘clotting studies’ or ‘DIC screen’ as requested by the clinicians on the ICU. Specimens for platelet-poor plasma were collected into 3 . 2% sodium citrate in the ratio of 1 part anticoagulant and 9 parts whole blood. The PT (normal 11 . 2–15 . 5 s), APTT (normal 23–35 s), thrombin time (TT) (normal 10 . 5– 15 . 5 s), fibrinogen (Fgn) (normal 1 . 5–3 . 8 g/l) and D-Dimer British Journal of Haematology , 1997, 98, 68–73 68  1997 Blackwell Science Ltd Correspondence: Dr C. H. Toh, Department of Haematology, Royal Liverpool University Hospital, Prescot Street, Liverpool L7 8XP.