Hoo Yee Yin
B.Pharm, M.Clin.Pharm, BCPS, R.Ph
Many people own a unit of point-of-care test (POCT) device for chronic diseases monitoring. POCTs are simple tests which can be done at home, in a pharmacy or other non-healthcare settings, without the need to send the blood or urine samples away to laboratory facilities. They are very convenient and results are made available immediately to patients.
In Malaysia, commonly seen POCTs in community pharmacies include blood glucose test, cholesterol test and pregnancy tests. In the United States, there are even more POCTs available in the pharmacies such as those to check hemoglobin level for anemia, hepatitis C virus antibody for hepatitis C detection, creatinine level for kidney function monitoring, HbA1C for diabetes monitoring, PCR for influenza and many more.
Many of the POCTs are used as preliminary screening tools in the US and patients can be referred to appropriate care if the results are positive. As many of these devices are being used for screening, individual pharmacy in the US involved in performing these tests is required to obtain a certificate of waiver from the authority* and the enforcement agencies monitor them closely.
New POCT technologies are appearing rapidly in recent years. But have you ever wondered how accurate are these tests? Take glucometer for example. Did you know that a glucometer should not be used to diagnose diabetes mellitus? Glucometer should only be used to monitor blood glucose concentrations in patients with confirmed diagnosis of diabetes. The general public should be aware of the fact that the glucometer results can be affected by operator, physiological and device factors.
Glucometer may elicit inaccurate results when expired test strips are used, or when the test strips are contaminated or compromised by very humid conditions; machine malfunction due to improper coding and/or calibration; testing in a very warm or very cold temperature; applying too little blood resulting in failure to cover the entire test strip with blood sample; physiological factors such as triglyceride levels, high or low hematocrit, hyperuricemia, dehydration, or drug interaction with electrodes (e.g. paracetamol).
The next time you enter a pharmacy to purchase a POCT device, do not just compare the price difference in different pharmacies. It is advisable to spend some time observing the models the pharmacists are using. If in doubt, do not hesitate to ask them how frequent they have to calibrate their device, how accurate is the test result and the specific measures to be taken to ensure result accuracy.
*Footnote: In US, Centers for Medicare & Medicaid Services (CMS) regulates all laboratory testing (except research) performed on humans in the U.S. through the Clinical Laboratory Improvement Amendments (CLIA).
- Kost, G. J., Tran, N. K. and Louie, R. F. 2008. Point-of-Care Testing: Principles, Practice, and Critical-Emergency-Disaster Medicine. Encyclopedia of Analytical Chemistry.
- Ginsberg BH. Factors affecting blood glucose monitoring: sources of errors in measurement. Journal of diabetes science and technology. 2009 Jul;3(4):903-13.