Q & A

January 2005

Richard A. Savage, MD, Editor

Q.  Is it acceptable to use sickle tested donor blood in lieu of commercial sickle-positive and -negative controls? If so, how long after expiration can donor blood be used as sickle controls?

A.  It is acceptable to perform hemoglobin electrophoresis or high-pressure liquid chromatography on a specimen up to seven days after the specimen is obtained if it is stored at 2-8°C. Expired units of donor blood far exceed that time frame and, therefore, may not provide valid results.

Commercial controls are lyophilized, and they must be used within about seven days of reconstitution. You can use fresh blood from a known abnormal hemoglobin patient, but you need to have appropriate consent, documentation (nature of the abnormality and infectious marker status), and patient safeguards. You could also collect known abnormal hemoglobin blood and lyophilize it, or make your own controls, but you would need to validate that your processing yields an acceptable product (like any manufacturer), assure any quantitation is linked to reference materials, and adhere to all the requirements for using a donor.

Chair, CAP Hematology/Clinical Microscopy Resource Committee

Q.  What are the easiest cost-effective instruments to use to set up a stat lab in an emergency department for chemistry and complete blood count tests?

A.  The old expression "give a man a fish and he'll eat for a day; teach him how to fish and he'll eat for a lifetime" applies to this question, as it might apply to purchasing equipment for any laboratory.

Rather than recommending specific analyzers, we believe it is more helpful to review the factors that should be considered when purchasing an analyzer so you can apply those factors to your particular situation. First, what tests are needed, and what will your test volume be? You mention chemistry and CBC, but you need to consider what specific chemistry tests the emergency staff want.^1,2 Testing for this purpose usually requires rapid turnaround time, so whole blood is the preferred specimen. However, if you desire tests that are not available on whole blood analyzers, centrifugation will be required and will delay results. Plasma specimens reduce the clotting delay and can usually be run on most analyzers, but this should be confirmed. When evaluating the turnaround time, consider the time to generate one set of results as well as the cycle time between specimens, particularly if volume will be heavy.

A number of vendors market blood gas analyzers that can also measure electrolytes and such analytes as glucose, lactate, urea, and creatinine using whole blood and potentiometric or amperometric electode-based methods.³ Not all vendors have the same test combinations, and not all electrodes behave as well as pH or sodium in these methods. Reviewing performance specifications, such as linearity and reproducibility, as well as getting user feedback on vendor performance and equipment support, are good ideas. Keep in mind that the equipment must operate 24 hours a day, so you need to determine how maintenance will be completed and how you will provide backup during downtime.⁴ Duplicating equipment can solve this issue, but if that is not possible, the service and support record of the company become even more important considerations. Furthermore, to ensure continued operation during a power failure, you'll want to plan for emergency power backup for the equipment.

Assuming the labor committed to this laboratory is a fixed expense, you'll want to focus on the cost of supplies associated with the different alternatives. This may, however, be secondary to turnaround time and dependability issues. Analyzers with disposable electrodes or test cartridges are usually easier to maintain but may be more expensive than those with reusable electrodes. If you envision doing bedside testing, a smaller, portable instrument is needed, and these usually come with a higher cost per test than those used in the central laboratory.

We have had success using the i-Stat analyzer (Abbott Point of Care) and the Hemoglobin Photometer (Hemocue Inc.) for out-patient pre-surgical testing; the Avoximeter 1000 E (Avox) for oxygen saturation in our catheterization lab; the Hemochron Jr. Signature (International Technidyne Corp.) for activated coagulation times on our patient floors and International Normalized Ratios in the cath lab; and the AVL Opti-CCA (Osmetech) for blood gases in our neonatal and pediatric intensive care units.

Our emergency center and other critical care areas are connected to the stat lab by vacuum tube, and the stat lab is equipped with Radiometer ABL 700 analyzers for blood gases, electrolytes, and glucose and a Sysmex SF 3000 for CBCs and differentials. Other vendors also offer suitable analyzers for these same tests, and your purchase decision may be based in part on past experience and personal preference.

Another consideration when selecting instruments is the personnel who will be doing the testing. If nurses are involved,⁵ the analyzers should be very user friendly, with prompts for operation, easy training, and minimal maintenance. You will want to restrict use to properly trained individuals and may, therefore, want operator identification or password protection security.⁶

You will also want a means to ensure proper recording of quality control and patient results. Connectivity is a buzzword in the laboratory equipment world and is important in terms of interfacing to a laboratory information system or local area network for reporting and record-keeping.⁶

Smaller point-of-care devices do not always have the same capabilities as larger analyzers in this regard. The ability to store patient results in the analyzer and upload them later is a great advantage when the LIS is down. You should also consider the ease of expanding the test repertoire of the analyzer as new tests become available from the manufacturer and whether the results from POC analyzers are equivalent to those from analyzers in the main laboratory, which is very important for tracking changes if a person converts from an emergency room patient to an inpatient.

Yours is not an easy decision, but fortunately, there are a variety of reputable vendors to choose from in this area of testing.

References

1. Aller RD, ed. Latest chemistry wish lists in low-volume labs: chemistry analyzers (for low-volume laboratories). CAP TODAY. 2004;18(4):44-58.
2. Aller RD, ed. Labs are hungry and hematology vendors are cooking: high-volume hematology analyzers. CAP TODAY. 2003;17(12):32-49.
3. Aller RD, ed. In vitro blood gas analyzers. CAP TODAY. 2004;18(7):15-36.
4. Kiechle FL, Case N. Cost benefit analysis for blood gas POCT. In: Kost GJ, ed. Principles and Practice of Point-of-Care Testing. New York, NY: Lippincott Williams & Wilkins; 2002:601-602.
5. Kiechle FL, Main RD. Point-of-care testing. In: Kiechle FL, Main RI, eds. Improving Efficiency in the Clinical Laboratory. Washington, DC: AACC Press; 2002:58-81.
6. Salka L, Kiechle FL. Connectivity for point-of-care glucose testing reduces errors and increases compliance. Point of Care. 2003;2:114-118.

Dr. Kiechle is an advisor to the CAP Publications Committee.