Benefits and Pitfalls of Point-of-Care Coagulation Testing for Anticoagulation Management

An ACLPS Critical Review

Geoffrey D. Wool, MD, PhD

Disclosures

Am J Clin Pathol. 2018;151(1):1-17. 

In This Article

Abstract and Introduction

Abstract

Objectives: Point-of-care (POC) testing is generally less precise and has higher reagent costs per test than laboratory-based assays. However, POC hemostasis testing can offer significant advantages in particular situations: patient-managed warfarin therapy as well as rapid turnaround time heparin management for intraoperative patients. Of note, POC hemostasis testing is generally approved for the purposes of anticoagulation monitoring and is inferior to laboratory coagulation testing for the diagnosis of congenital or acquired coagulopathy.

Methods: The frequently used POC coagulation instruments for POC international normalized ratio and activated clotting time are reviewed, as well as their typical performance relative to central laboratory testing (where available).

Results: Several cases are discussed that highlight the benefits, as well as pitfalls, of POC coagulation testing.

Conclusions: POC coagulation testing for anticoagulation monitoring offers advantages in particular situations. Clear policies and protocols must be developed to guide proper use of POC versus central laboratory hemostasis testing.

Introduction

Point-of-care (POC) testing is performed at or near the site where clinical care is delivered, typically by personnel whose primary training is not in clinical laboratory science (to include patients performing self-testing). POC testing can provide significant benefits in the form of improved time to test result/diagnosis or smaller specimen volume requirements. These improvements are particularly helpful for patients in certain settings: intraoperative patients, patients with immediately life-threatening illness, and outpatients with chronic illnesses or medications that can be managed at home/nearby with the help of POC testing. Generally, the precision of POC systems is lower than that achieved with automated laboratory systems. In addition to increased imprecision, POC testing may also show bias relative to laboratory assays. This lesser performance as well as higher cost per test must be weighed against any clinical/logistical advantages of a POC device. When considering POC testing, it is critically important to determine whether or not the imprecision and bias of POC testing are associated with clinically meaningful differences in test results relative to laboratory assays.[1]

Depending on the assay's Clinical Laboratory Improvement Amendments (CLIA) status, POC testing can be performed in the hospital, clinic, or home. Testing in the home requires US Food and Drug Administration (FDA) approval with waived status; clinics and hospitals can use waived or moderate-complexity POC testing based on their staffing and accreditation. Regardless of the setting of POC use, testing is often performed by nonlaboratory personnel with less experience in quality control, in a less controlled environment than a typical clinical laboratory. POC testing can be plagued by insufficient calibration, quality control (QC), maintenance, and documentation.[2] The possibilities of preanalytic, analytic, and postanalytic errors are all potentially increased in the POC setting.

POC testing must be undertaken within the confines of safe practice involving adequate quality control procedures, competent testing staff (including well-trained self-testers), and use of POC assays solely in the patient population for which the POC assay was approved and valid. POC testing instruments typically have automatic system verification procedures. However, whether so-called electronic QC or true liquid QC is used differs by instrument and CLIA approval status. Nonwaived assays require liquid QC; if an assay manufacturer recommends performing liquid QC less frequently than daily, Centers for Medicare & Medicaid Services may require an Individualized Quality Control Plan to ensure that the risks of less frequent QC performance are identified and mitigated.

Some laboratorians strongly feel that POC coagulation testing has a very limited role in a hospital setting (limited essentially to activated clotting time [ACT]), given the abilities of most central laboratories to provide a full menu of coagulation testing with rapid turnaround time (TAT).[2] POC testing can potentially be performed in the hospital with a high level of quality and provide a unique and important role in patient care.[3] In some ways, POC testing has more complex logistics and management in the hospital setting than tests performed on automated central laboratory platforms. Therefore, collaboration between laboratorians and their clinical colleagues is essential if POC testing is to be safely and effectively used. Quality assurance must be properly overseen and include internal and external quality control procedures, staff training and competencies, regular audits, and complete and accurate documentation.[4]

POC testing, be it in a hospital/clinic setting or within a patient's home, should only be embarked upon after careful patient selection. Overall quality of clinical care is only enhanced by POC testing if the appropriate patient population is selected, will benefit from the test, and, in the case of in-home POC testing, is able to accurately and properly perform testing themselves. Patients with unusual or potentially unreliable POC testing results must be referred to central laboratory testing and, if necessary, to designated medical care.

In the field of hemostasis, determining the comparability of POC coagulation testing to laboratory results is particularly confusing due to different testing samples (capillary whole blood [WB] vs platelet-poor plasma) or due to entirely different assays being used to measure the same analyte (POC ACT vs laboratory activated partial thromboplastin time [aPTT] to measure lower dose unfractionated heparin [UFH]). POC coagulation devices themselves have different properties, and systems are not interchangeable.[5] With this basis for considering the complexities of POC hemostasis testing, consider how important accuracy is for anticoagulation monitoring. The consequences of missing a high or low international normalized ratio (INR) could be catastrophic and irreversible, and in both cases, the patient may not have warning symptoms to herald the bad outcome.[73]

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