Advances in Point-of-Care Testing


Vol. 19 • Issue 10 • Page 32

POCT

The widespread use of point-of-care testing (POCT) has become feasible thanks to improvements in the ease of use of instruments and enhancements in automation. In many cases, software applications have been incorporated into the instruments to provide automated calibration and quality control. These software enhancements have also aided the availability of security and quality assurance with the lockout feature that requires operator identification, lot number verification, operator training verification, etc.

There’s also been a shift away from the use of liquid reagents to solid-phase reagents and electrochemical methods. The analyzer systems mostly require whole blood and this removes the need for centrifugation, thus further simplifying the use of the POCT devices. Many devices now require fewer steps for analysis and reduced test times. As a result, many POCT devices are now CLIA-waived.

On the Market

In recent years, a variety of easy-to-use handheld and table-top devices have been developed. One of the most well-known hand-held POCT device is the i-STAT Clinical Analyzer (Abbott). The number of tests available on the i-STAT continues to increase. Some of the new additions to the test menu include coagulation (ACT kaolin, ACT Celite® and PT/INR) and cardiac markers (cTnI, CK-MB and BNP).1 In addition, the system can now be interfaced with many major LIS/HIS systems so that patient results can be uploaded to their electronic medical records.

Another new entrant into the field of hand-held devices is the epoc® (Epocal Corp). This device can be used to measure pH, pCO2, Na+, K+, Ca2+, glucose, lactate and hematocrit.2 The cartridges are stored at room temperature and patient results can be transmitted to the laboratory LIS/HIS via a data manager.

Expanding Test Menu

Some manufacturers with extensive record in the field of POCT analyzers have improved the test menu on their blood gas analyzers by adding critical care tests. Lactate has been added to the test menu for some analyzers (e.g., ABL 90 FLEX® – Radiometer America Inc).3 The turnaround time has been shortened remarkably and the required sample volume minimized.

The fecal occult blood test, important in the diagnosis of colorectal cancer, has undergone improvements. Immunoassays that are specific for human hemoglobin have been developed. These tests are more specific for hemoglobin and less sensitive to interferences from non-hemoglobin peroxidases present in vegetables and ingested meat. The sensitivity and specificity of these assays at ≈ 99.2% and 96.7% are also much higher than that of traditional guaiac-based tests at 40%. Examples of available devices include acutest® IFOB,4 Hemoccult® ICT,5 Hemosure IFOB6 and Insure® fecal immunochemical test.7

Diabetes Tests

The Standards of Medical Care in Diabetes issued by the American Diabetes Association recommends the use of glycated hemoglobin (HbA1C) for the diagnosis of diabetes mellitus.8 This is in addition to its use for the follow up of these patients. It is expected, therefore, that there will be an increase in the number and variety of these HbA1C POCT devices.

POCT devices for the measurement of HbA1C were evaluated recently9 and several were found not to meet the National Glycohemoglobin Standardization Program certification criteria. It is likely that manufactures will improve the analytical performance on available instruments to meet demands from clinicians.

New POCT devices for the measurement of albumin/creatinine ratio have been developed that will be useful in the management of diabetic patients and will reduce the need for several hospital visits for the measurement of this albumin and creatinine prior to clinic attendance.

Chronic Kidney Disease

Chronic kidney disease (CKD) is present in >16.8% of American adults older than 18; the National Kidney Disease Education Program (NKDEP) recommends the automatic reporting of estimated glomerular filtration rate (eGFR) to identify patients with CKD early and institute appropriate treatment.10

In light of this recommendation, it is expected that POCT devices providing eGFR measurements will be manufactured. One such device was recently launched by Nova Biomedical and was christened StatSensor® Xpress Creatinine.11 This device utilizes biosensor technology and whole blood to produce creatinine measurement and eGFR results. According to the manufacturers, the device can be interfaced to an LIS via a connectivity meter. A rapid ELISA kit for the measurement of Neutrophil Associated Gelatinase Lipocalcin in plasma and used in the early diagnosis of acute kidney injury is also available.12 This likely will be developed into a POCT in the near future.

Oral Specimens

Saliva is an ultrafiltrate of blood that can be used for biochemical assays. In recent times, oral fluid testing has become popular for drugs-of-abuse screening because it offers rapid detection of drugs and is relatively tamper resistant. Results obtained are usually as good as those from serum specimens. A POCT hand-held device using saliva (Oral-View® Saliva Multi-Drug of Abuse Test)13 is a rapid immunoassay and may be useful in detecting very recent drug usage.

A Look Ahead

POCT devices that offer rapid detection of microorganisms used in bioterrorism may soon be developed. Currently, rapid immunochromatographic test strips are available for testing of colony suspensions for Bacillus anthracis and other bioterrorism organisms (Biothreat Alert® Test Strips – Tetracore Inc).14 As well, strips used for detection in serum or other body fluids may be developed. POCT will continue to be driven by technology and the need to produce results in a timely manner to improve patient outcome.

Adetoun Ejilemele is clinical chemistry fellow, and Dr. Okorodudu is professor of Pathology and director, Clinical Chemistry, Department of Pathology, University of Texas Medical Branch, Galveston.

References

1. http://www.abbottpointofcare.com/

2. http://www.epocal.com/system.html

3. http://www.radiometeramerica.com/abl-90flex

4. http://www.accutest.net/products/pdf/ifobt-dual-Package-Insert.pdf

5. http://www.beckmancoulter.com/literature/ClinDiag/1_395 069-F.pdf

6. http://www.whpm.com/insert_pdf/iFOB.pdf

7. http://www.insuretest.com/subpages/sensitivityandspec.html

8. Standards of Medical Care in diabetes – 2010. A Position Statement by the American Diabetes Association. Diabetes Care 33:S11 – S61; 2010.

9. Lenters-Westra E and Slingerland RJ. Six of Eight Hemoglobin A1C Point of Care Instruments do not Meet the General Accepted Analytical Performance Criteria. Clin Chem 56(1):44-522010.

10. http://www.kidney.org/professionals/kdoqi/guidelines_ckd/p1_exec.htm

11. http://www.novabiomedical.com/products/strip_based_clini cal_analyzers/statsensor_creat.php

12. NGAL_Rapid_ELISA_Kit_(KIT 037)_Brochure[1].pdf

13. http://www.alfascientific.com/alfa-products/drugs-of-abuse/saliva-doa

14. http://www.tetracore.com/pdfs/Tetracore_RedLine_Alert_Test.pdf

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