Return to CAP Home
Printable Version

  Q & A

title

 

 

 

cap today

September 2004

Richard A. Savage, MD, Editor

Q. Our emergency department insists that the department of pathology allow ED nurses and physicians to perform B- natriuretic peptide, troponin, myoglobin, and b-hCG as point-of-care testing to improve efficiency and decrease patient treatment delays. Our average in-lab turnaround time for all ED stat testing is 30 to 50 minutes. We recently began using dedicated ED-to-laboratory couriers to transport specimens, thereby decreasing delivery time to less than five minutes.

We have determined that POC test kits and their related expenses can cost over $130,000 more than central lab testing. Although such testing might provide slightly quicker TAT for test results, the quality and accuracy of those results concern us.

ED stat labs are a great idea on paper, but many end up closing because it is expensive to duplicate central lab processes. Is POC testing headed for the same fate? Under what circumstances would POC testing be worth the increased costs? Can POC testing improve patient care when central lab TAT is under one hour?

A.  Emergency department overcrowding, with its inevitable effect on patient care, has reached crisis levels in the United States. Hospitals seeking solutions usually focus on ED operations, inpatient bed availability, and supporting ancillary services, such as laboratory and radiology. Only a few studies in peer-reviewed journals have documented how point-of-care testing affects ED operations or patient outcomes.1-6

Most studies illustrate that POC testing decreases turnaround time and improves physician satisfaction, but results with regard to its impact on ED operations are mixed. A subset of studies has shown that POC testing may decrease length of stay in the ED and hasten medical decisionmaking.3,4,6 As more tests become available in POC formats, such as cardiac markers, BNP, and D-dimer, the opportunities to improve medical outcomes and hospital operations continue to expand. For example, in one study, TAT decreased an average of 52 minutes (from 60 minutes to eight minutes) after implementation of POC testing for pregnancy, glucose, urine dipsticks, and cardiac markers in an ED satellite laboratory, and ED length of stay decreased an average of 41.3 minutes for each patient tested.6 Presumably, this translates into more ED beds being available for patient evaluation, a decline in the number of ED divert hours, which is when ambulances are diverted to other hospitals, and possibly an increase in hospital revenue.6,7

Many factors must be considered before implementing POC testing, including physician satisfaction with the central laboratory, required TAT by ED physicians, confidence in the accu racy of POC results, patient population, test menus, and which personnel will perform the POC testing. A pro cess-improvement team with representatives from the ED, laboratory, and administration should be established to evaluate the potential pros and cons of such testing. A pilot study may help some hospitals de termine the usefulness of POC testing.

As pointed out, the cost of POC testing, as opposed to central laboratory testing, is an issue that has plagued POC testing from its outset.7 In our institution, the unit cost of ED POC testing was estimated to be 6.5 times more expensive than laboratory testing. In some cases, such as rapid cardiac markers, BNP, and rapid influenza testing, the cost of reagent cartridges can be comparatively high. However, measuring unit cost fails to consider how the improved TAT affects hospital operations. Although little data is available comparing the system cost of POC testing to that of the clinical laboratory, we believe that this comparison is more relevant to the issue of true cost than conventional estimates of unit cost based on considerations of labor and consumable expenses in isolation.

Many hospitals have successfully implemented POC testing in the ED. The menu of tests varies as does the personnel performing the testing. As the advantages of POC testing are reported in peer-reviewed literature, this trend may continue. Although some studies have shown that the cost of POC testing is outweighed by decreased TAT, decreased ED length of stay, increased physician satisfaction, and improved patient outcomes, each institution must evaluate its situation to arrive at an appropriate conclusion.6

In summary, implementing POC testing in the ED can be beneficial to selected outcomes but should be targeted to a specific menu and integrated into overall ED operations.

References

  1. Peredy T, Powers R. Bedside diagnostic testing of body fluids. Am J Emerg Med. 1997; 4: 400-407.
  2. Parvin C, Lo S, Deuser S, et al. Impact of point-of-care testing on patients' length of stay in a large emergency department. Clin Chem.1996; 42: 711-717.
  3. Murray RP, et al. Effect of point-of-care testing in an adult emergency department. J Emerg Med. 1999; 17: 811-814.
  4. Kendall J, Reeves B, Clancy M. Point-of-care testing: Randomized controlled trial of clinical outcome. BMJ. 1998; 316: 1052-1057.
  5. Kilgore M, et al. Evaluating STAT testing options in an academic medical center: Therapeutic turnaround time and staff satisfaction. Clin Chem. 1998; 44: 1597-1603.
  6. Lee-Lewandrowski E, et al. Implementation of point-of-care satellite laboratory in the emergency department of an academic medical center: Impact on test turnaround time and patient emergency department length of stay. Arch Pathol Lab Med. 2003; 127: 456-460.
  7. Lee-Lewandrowski E, et al. Point-of-care testing: An overview and a look to the future. Clin Lab Med. 2001; 21: 217-239.

Stacy Foran Melanson, MD, PhD
Associate Medical Director,
Clinical Chemistry
Brigham and Women's Hospital
and Harvard Medical School,
Boston

Kent B. Lewandrowski, MD
Associate Chief of Pathology and Director of Core Laboratory,
Massachusetts General Hospital
Associate Professor,
Harvard Medical School,
Boston
Member, CAP Point-of-Care
Testing Committee

Q.  Fetal-maternal hemorrhage has been evaluated by the Kleihauer-Betke acid elution test and, more recently, by flow cytometric methods. The co-oximeter on our gas analyzer can measure fetal hemoglobin. Has anyone evaluated the possibility of using this rapid method for this purpose in emergency settings?

A.  Whole blood fetal he mo glo bin measurements are generally not useful for detecting fetal-maternal hemorrhage because they do not provide information on the pattern of cellular distribution of fetal hemoglobin. Such methods measure the percentage of fetal hemoglobin in whole blood lysates. Because normal adults have a low percentage of fetal hemoglobin distributed in variable amounts in a subset of red cells, or so-called “F-cells,” distributed within the red cell mass, there is a background range of fetal hemoglobin (often cited as 0.2 to 1.0 percent) that will be detectable in otherwise healthy individuals.

On the other hand, fetal red cell quantitation tests-either by acid elution/ Kleihauer-Betke method or flow cytometry-do not measure the percentage of fetal hemoglobin, but instead measure the percentage of cells that contain enough fetal hemoglobin to resist acid elution, as in the case of the K-B assay, or to show up as a distinct cell population by flow cytometry using HbF antibodies. When these methods are used to examine patient samples, the fetal red cells will show up as discrete populations, but at a low percentage, often not exceeding one percent, even in the presence of active fetal-maternal hemorrhage. Because healthy individuals may exhibit this percentage of whole blood fetal hemoglobin, it would not be feasible to establish useful cutoff values for detecting fetal-maternal hemorrhage using whole blood methods.

There is no widely accepted alternative to acid elution testing or flow cytometry for quantifying circulating fetal red cells. However, many laboratories employ very sensitive screening methods, such as rosette testing, that can abrogate the need for quantitative testing of patients with negative screens. Some laboratories use a semiquantitative gel agglutination assay that yields numerical result ranges for circulating fetal red cells. However, this method is only applicable for detecting Rh(D)-positive fetal red cells in the circulation of an Rh(D)-negative mother for purposes of Rh immunoglobulin administration. Furthermore, the gel agglutination test requires quanti tative confirmation by K-B or flow cytometry above a certain level of positivity.

For laboratories that do not routinely perform fetal red cell detection assays, many flow cytometry laboratories will accept fetal red cell detection requests on an outreach basis. These tests obviously are not usually available with a stat turnaround time, but they can be available well within the time threshold necessary for administering Rh immunoglobulin to an Rh(D)-negative mother.

William G. Finn, MD
Clinical Associate
Professor of Pathology
University of Michigan Medical School
Ann Arbor
Member, CAP Hematology/Clinical Microscopy Resource Committee