Validation of Current Practice and a near Patient Testing Method for Oral-Anticoagulant Control in General Practice

Abstract

When oral anticoagulant control is monitored in general practice, venous blood samples are usually transported to a central laboratory for determination of international normalized ratio (INR). An alternative is near patient testing by a commercial method. In a rural general practice 27 km from a central haematology laboratory, whole blood samples were drawn from patients receiving oral anticoagulants and analysed by three methods: after centrifugation, plasma separated and frozen in liquid nitrogen, transported to the laboratory, thawed and immediately analysed (control); courier transport of citrated sample to the laboratory for analysis (routine); near patient testing of whole blood sample (NPT). Maximum temperature achieved and time to analysis for routine samples were recorded. 306 complete sets of data were obtained. Comparison between the routine method and the control method revealed acceptable agreement. On multiple regression analysis, maximum temperature achieved did not contribute to differences observed but time to analysis of over 5 hours did make a significant contribution. Comparison between the NPT method and control method showed acceptable agreement, with persistent underrecording by the NPT method. The routine method for INR determination was validated as robust and reproducible with the proviso that needleto-analysis time should be kept below 5 hours. The NPT method was valid under conditions of normal general practice. Strict quality control of NPT methods is essential if performance is to be comparable with that of established methods.

The impact of non‐vitamin K antagonist oral anticoagulants (NOACs) on anticoagulation therapy in rural Australia

“…There have been few RCTs in this area and none have investigated all the areas covered in this Trial or at the scale of this Trial either in terms of the number of practices, the number of patients or the number of pathology tests included. 8,18,33,34,[58][59][60] No past trials and very few observational studies 16,17 have investigated the influence of geographic location on PoCT. The results of the PoCT Trial should provide a sound evidence base as to whether PoCT (for the three conditions) should be implemented by the government in Australian general practice.…”

“…44 Four of the RCTs investigated PoCT with another intervention. 8,18,21,34,58,59 The geographical setting included the United Kingdom (n=13) 8,16,18,21,33,[60][61][62][63][64][65][66][67] , Australia (n=7) 17,23,47,[68][69][70][71] , USA (n=5) 44,58,[72][73][74] , Belgium (n=2) 34,59 , Sweden (n=1) 75 and Ireland (n=1). 76 A description of the 29 studies included in the review is reported in Table 13 and Table 14.…”

“…18 The mean bias between PoCT and laboratory values was assessed in all six studies with three 18,62,63 detecting an overestimate of the PoCT INR result compared to the laboratory and three 16,17,76 found an underestimate. Four of the six studies investigated the correlation between PoCT and laboratory values with all concluding that the results were adequate 16,17,62,63 .…”

“…18 The mean bias between PoCT and laboratory values was assessed in all six studies with three 18,62,63 detecting an overestimate of the PoCT INR result compared to the laboratory and three 16,17,76 found an underestimate. Four of the six studies investigated the correlation between PoCT and laboratory values with all concluding that the results were adequate 16,17,62,63 . In four studies Bland Altman plots were performed [16][17][18]62 but only two studies 16,62 reported the 95% limits of agreement between PoCT and laboratory and only Seamark et al 16 Three studies 69,71,72 reported the safety of PoCT diabetes testing.…”

“…Four of the six studies investigated the correlation between PoCT and laboratory values with all concluding that the results were adequate 16,17,62,63 . In four studies Bland Altman plots were performed [16][17][18]62 but only two studies 16,62 reported the 95% limits of agreement between PoCT and laboratory and only Seamark et al 16 Three studies 69,71,72 reported the safety of PoCT diabetes testing. Schwartz et al 72 showed the mean HbA1c result of the PoCT device to be significantly higher compared to the laboratory.…”