Abstract

Laboratory techniques used in the control of oral anticoagulant therapy were compared at five centres. The methods studied were: (a) prothrombin-proconvertin (`P and P') technique with the centres using their own reagents. This resulted in major discrepancies between the centres. (b) P and P technique with all the centres using centrally supplied reagents. The discrepancies noted under (a) disappeared when (b) was employed. (c) Thrombotest: the centres used the same batch of reagent and the specimens were transmitted in glass or polystyrene containers. The centres obtained closely comparable results, whether transportation was in glass or polystyrene. (d) Onestage `prothrombin' time with all the centres using the same reagents. When the results were read from a dilution curve there were discrepancies between the centres.

For comparability of results between centres using anticoagulant therapy, centrally supplied P and P reagents or Thrombotest should be used. Since only the latter was commercially available as a centrally standardized reagent at the initiation of this trial, it emerged as the method of practical choice at the time.