Point of Care Method for the Determination of Dabigatran in Urine Samples From Patients On Treatment.

Abstract 2270

Dabigatran is effective and safe for prevention of thromboembolism in several indications at daily fixed doses not requiring laboratory dose adjustment. However, it may be necessary to determine its activity/concentration in specific patient populations by specific assays from plasma samples. A point of care (POC) method may offer advantages by providing immediate results to facilitate medical decisions for acute therapeutic interventions.

Plasma and urine samples were taken from patients on treatment with 110mg or 150mg dabigatran bid (n=110) and healthy persons (n=144) after having given written informed consent. Dabigatran was purified from commercially available Pradaxa® and its purity was characterized by analytical methods and S2238 thrombin specific chromogenic substrate assay and Hemoclot assay containing dabigatran standards. The S2238 assay was also used for the determination of dabigatran in plasma samples of patients and healthy persons using one purified dabigatran as standard. The lower limit of detection was 0.06μg/ml plasma. In urine dabigatran was determined by a POC method incubating the lyophilized reagents on mini-strips followed by incubation with patient‘s urine (international patent application No PCT/EP2012/002540). The development of colour of urine samples was determined 10 min after incubation with reagents quantitatively by optical density (OD) measurement and qualitatively as judged by eye according negative and positive colour (three independent readings by SD, SK, CG, and photographic documentation). To determine the positive and negative predictive value (PPV and NPV) of plasma samples, a cutoff value of <0.06μg/ml dabigatran was defined. The PPV and NPV of POC method was determined for urine samples of the control and treatment group according positive and negative development of colour as judged by eye reading.

Control persons (n=144) displayed plasma concentrations of 0.04+0.03 μg/ml (mean, standard deviation) of whom 128 had values below the cutoff value <0.06 μg/ml. Sixteen patients had values above this cutoff. Accordingly, the NPV for correct negative results in controls was 88.9%. In patients on therapy the concentration of dabigatran was 0.12+0.08 μg/ml (n=107). 102/107 patients had plasma concentrations of dabigatran above the cutoff value of 0.06 μg/ml and 5 patients below the cutoff-value. This results in a PPV of 95.4%. Using the POC method for dabigatran in urine all of 144 control persons had negative values with OD measurement (0.803+0.116 OD units) and eye measurement. The NPV for control persons was 100%. During therapy with dabigatran, all 110 patients had positive colour development as judged by eye corresponding to an OD of 0.219+0.161. Accordingly, the PPV was 100% for patients on treatment with dabigatran. Limitations of the POC methods are the lack of information about the compliance of the patient and severe renal impairment. The validation of the POC assay by patients is ongoing.

The POC method of patients on treatment with dabigatran improves the NPV and PPV from about 90% with plasma samples to 100% using urine samples, respectively. The method is non-invasive, rapid, and specific, can be repeatedly performed and may be used by medical personal and patients. The development of colour is different from the POC method for rivaroxaban.