XBC

By Renee DiIulio

Blood analysis is so ubiquitous in health care that even regular watchers of television shows, such as “ER,” know the terms CBC (complete blood count) and hemoglobin (Hb), whether or not they know what they measure. Physicians order blood cell counts for both routine and emergency patients. According to market research completed by Chempaq A/S of Copenhagen, Denmark, CBCs are ordered more than 200 million times annually in the United States. The information is used to determine a person’s general health and nutritional status, and to help screen for disorders, such as anemia and infection.

In real life, only partly dramatized on television, a blood sample is drawn and delivered to the hematology lab to obtain the results of a blood cell analysis. For referring physicians with no on-site laboratory, the wait can negatively impact patient care; even hospital doctors must allow time for transportation and other logistics. Yet some parameters of the test can indicate an immediate course of treatment. For instance, if platelets are low, the patient may be at risk of excessive blood loss. If white blood cells are high, the patient may be suffering from an infection. If hemoglobin is low, the patient may need a blood transfusion.

A new blood analyzer from Chempaq recently launched in Denmark, the Chempaq XBC (eXpress Blood Counter), brings a portion of blood cell analysis to the point of care, eliminating intermediate steps and reading results in 3 minutes. The product is expected to receive US FDA 510(k) clearance this year.

Counting with the Coulter Principle
In the first half of the 20th century, cell counts were conducted by eye, using microscopes and stained blood smears. In 1949, Wallace Coulter discovered the Coulter Principle, allowing automation of this type of analysis, which he patented in 1953. During the late 1950s, automated cell counting equipment revolutionized this aspect of patient care. At first, the system counted only red blood cells; later technological advances allowed white blood cells counts; and finally, in the 1970s, platelet measurements were counted.

The Coulter Principle sizes and counts suspended particles by measuring their electrical resistance. A sample flows through an aperture created by electrodes at a controlled rate. As each particle passes through, it displaces its own volume of electrolyte, which is then measured as a voltage pulse. The height of each pulse is proportional to the volume of the particle. Several thousand particles can be counted per second, allowing the test to be conducted much more quickly and accurately then when counted by hand.

Automation brought the same benefits then as it does today: faster turnaround, more efficient workflow, fewer time demands on staff, and cost savings. Of course, those benefits initially came in a very large system, which has, over time, been reduced in size to fit on a countertop.

Chempaq has decreased this footprint even further, creating an analyzer the size of a desk telephone that measures five blood cell parameters: the white blood cell count, or leukocytes (WBC); a three-part WBC differential, measuring lymphocytes, monocytes, and granulocytes; and hemoglobin.

The Five Parameters
Abnormal results in any of these areas can indicate significant health problems. The WBC count, which measures the actual number of white blood cells per volume of blood, can be high or low depending on the condition. A normal WBC count falls between 4,000 and 10,000 white blood cells per cubic millimeter of blood.

Leukocytosis, or an elevated WBC count, could be the result of infection, leukemia, or dead tissue resulting from a heart attack, burns, or gangrene. Leukopenia, or a low WBC count, may indicate problems with the bone marrow or a disease of the immune system, such as HIV or AIDS.

The WBC differential provides information about the type and frequency of different white blood cells present in the blood. Many hematology lab technologists are able to identify these cells by sight, but it is done more quickly with automation. The Chempaq XBC offers a three-part WBC differential, providing information about lymphocytes, monocytes, and granulocytes.

Lymphocytes are responsible for the body’s immune response and typically represent roughly 16%–48% of the total WBC differential.¹ Monocytes ingest foreign material and usually make up 1%–10% of the WBC differential.¹ Granulocytes, with a normal range of 35%–75%, provide nonspecific immune response activity. These cells include neutrophils, eosinophils, and basophils, which are identified by the staining features of their granules.¹

“Over time the information derived from the WBC differential count has become a cornerstone in laboratory hematology and is widely used for screening, case finding, diagnosis, and monitoring of hematologic and nonhematologic disorders. It is used, for example, in diagnosis of bacterial or viral infectious diseases; evaluation of allergic conditions; diagnosis and monitoring of malignant diseases, such as leukemia; and staging of HIV infection. The WBC differential count is often also used to monitor a patient’s progress and/or response to treatment.”¹

Automating the WBC differential has improved its efficiency and increased its accuracy through use of a larger sample size. The traditional manual method has been one of the most expensive routine tests in the clinical hematology laboratory due to its time-consuming and labor-intensive nature.¹

Hemoglobin, which correlates to the red blood cell count, is as routine as the WBC differential, though not as resource-intensive. Low hemoglobin indicates anemia and can explain symptoms such as fatigue. In a trauma patient, a low result may indicate the need for a blood transfusion.

One Drop in the PAQ
The Chempaq XBC determines the hemoglobin level with photometry. The remaining parameters are measured with a patented sensor technology based on the Coulter Principle. The Chempaq modification avoids complex liquid handling, enabling the system to be particularly compact. The product has been in development since 1999, stemming from the PhD work of Chempaq’s founder, Ulrik D. Larsen, now the company’s chief technical officer. This early research occurred in the Microelectronics Center (MIC) at the Technical University of Denmark (Lyngby, Denmark).

The actual counting occurs within a small disposable cassette or particle analyzer and Quantifier (PAQ), which requires only a drop (or approximately 20 microliters) of capillary blood. This can be collected from a finger stick or a venous blood sample mixed with EDTA. The blood is drawn into the PAQ through capillary action and is then mixed with a reagent and directed through an aperture, where it collects in a third chamber. The system self-calibrates and completes the cell count, measuring the hemoglobin last.

The process does not begin until the PAQ is inserted into the reader. The user pushes a button, closing the lid automatically and starting the process. The reader controls the electrical and fluid operations with air pressure through connectors in the PAQ cradle. Measurements are made through optical detectors.

The results are available in 3 minutes. “The entire process, including sample-taking, takes less than 4 minutes,” says Jakob Moller Jensen, business development manager for Chempaq. “Physicians have typically had to wait 1 to 3 days for these results to be analyzed traditionally.”

A Market of 500 Million
The new product is not only faster but also simpler: A physician can perform the test himself or herself within the confines of the office. “A general practitioner will experience increased support in the diagnosis of a patient—on the infection status, for example,” says Jensen.

Office physicians will be the first group Chempaq targets, according to Jensen. Future markets will include oncology, emergency rooms, intensive care units, and pediatric and neonatal units. Chempaq market research found the global need for CBCs in these niches to be more than 500 million tests annually.

All markets can benefit from the information immediately available with this test. In addition, the next model of the Chempaq XBC will feature data management, increasing its versatility for larger facilities.

The test is not intended to supplement laboratory testing, but rather to stand on its own and improve patient treatment. Used on its own, the expense is comparable to that of a laboratory test. “Pricing, which for the United States will be set after FDA clearance, is reasonable compared to the factors in the cost of a lab test, such as salaries, reagents, and even depreciation,” says Jensen.

“In principle, we’ve used off-the-shelf technology to provide a point-of-care test that delivers a quick answer to the physician and permits faster evaluation of a patient’s condition,” says Jensen. Faster answers mean faster treatment and improved patient care—as easy as 1-2-3.

Renee Dilulio is a contributing writer for Clinical Lab Products.

Reference
1. Houwen B. The differential cell count. Laboratory Hematology. 2001;7:89-100. Available at: www.bloodline.net/stories/storyReader$2898. Accessed on February 3, 2005.