The impact of point-of-care testing on the diagnosis of infectious diseases - Lab Management

Medical Laboratory Observer, August, 2003 by Robin G. Weiner, Julia K. Tyler

Rapid or point-of-care testing (POCT) in the identification and management of infectious diseases is a hot topic worldwide. Medical, political, media and lay people are paying close attention to POCT technology developments in both conventional and highly novel contexts. Not since smallpox, polio and tuberculosis were daily risks in the developed world, have infectious diseases been as high on the list of public health priorities as they are today.

From the advent of HIV/AIDS in 1981 to the emergence in the new millennium of potent influenza strains and fears about "weaponizing" a multitude of organisms, it has become increasingly obvious that successfully identifying and conquering the "old" infectious diseases has not put an end to easily transmissible and lethal diseases. In the United States alone, a nearly century-long decline in deaths from infectious diseases has been reversed; deaths rose 58% between 1980 and 1992 (see graph). The pathogens involved run the gamut from routine but bothersome, to highly lethal. They cause widespread suffering and death; cost governments, insurers and individuals billions of dollars in direct medical costs; disrupt commerce, tourism and other economic activities; and threaten the stability and growth of less-developed countries. More often than not, there are effective therapies for these diseases--effective, that is, if clinicians could diagnosis symptomatic patients rapidly and accurately. Recent experience with Severe Acute Respiratory Syndrome (SARS) also is a reminder that, even when available therapy is less than optimal, the ability to identify contagious individuals and enforce a quarantine saves lives.

What impact do POCT technologies have on managing infectious disease? There are two distinct viewpoints. The first is that of the clinician who wants to be able to provide better patient care in routine practice situations. The second is that of clinicians, public health officials and others who work with both real and anticipated scenarios--like SARS, monkeypox, West Nile virus, or weaponized influenza--that are clearly being encountered more often. Both of these stakeholder groups benefit from access to POCT technology currently in world markets, creating enormous pressure on innovators to develop rapid diagnostics where none currently exist.

POCT: improving patient outcomes

As the number of rapid tests has increased, so has the number of situations in which use of these tests can make a real difference in infectious disease management. A few examples:

* Group B Streptococcus (GBS), the most common cause of life-threatening infections in newborns, can be transmitted from an infected mother to an infant during delivery. One in every 20 newborns with GBS dies. Babies that survive, particularly those who have meningitis, may have long-term problems, such as hearing or vision loss or learning disabilities. While GBS can be diagnosed and treated in pregnant women, many women in the United States and elsewhere still have no prenatal care and arrive at the hospital for delivery with GBS infections. Rapid GBS testing (15 minutes from test to result) in the delivery room allows physicians to identify infected women and push IV antibiotics before delivery that may prevent GBS transmission as the baby moves through the birth canal.

* HIV testing. Results from conventional HIV antibody screen tests are generally not available for one to two weeks. POC tests for HIV infection, on the other hand, allow the diagnosis to be made in 10 minutes, while the individual is still present. This turnaround time can be critical. According to the Centers for Disease Control and Prevention (CDC), up to 25% of HIV-positive persons and 33% of HIV-negative persons testing at publicly funded clinics do not return for their test results and do not receive counseling about medical treatment or the need for behavioral change. Use of a POCT with immediate results substantially increases the number of people who know their HIV status and receive information about next steps. (1)

* Respiratory Syncytial Virus. RSV is a highly contagious, acute, viral infection of the respiratory tract that can become a problem when it is severe or leads to complications. Babies--especially those born prematurely--immunocompromised individuals, and older adults are at increased risk of complications. RSV is the leading cause of hospitalization of children during the first year of life. Infection involving the lower respiratory tract carries an associated mortality rate of 0.5%, especially in premature infants or infants and children with underlying lung disease. Because RSV's flu-like symptoms are also typical of many other diseases, quick and accurate diagnosis is important to determining optimal treatment. Rapid immunoassays using highly sensitive monoclonal antibodies specific for RSV antigens can be run in a physician's office, an emergency department or clinic in 15 minutes.

* Influenza and the new importance of "flu-like" symptoms. Most people who get the flu recover completely in one to two weeks, but some develop serious and potentially life-threatening medical complications, such as pneumonia. According to the CDC, 36,000 people die and approximately 100,000 people are hospitalized each year from influenza in the United States alone. Rapid flu tests are fast and accurate ways to test for influenza, particularly in anticipation of new strains developing--or being developed as an instrument of bioterror. Use of rapid flu tests prevents unnecessary use of costly therapeutics and slows the rate at which essential antibiotics become ineffective. Recent concerns about inappropriate antibiotic prescribing have led many in the medical leadership to make this a priority message for clinicians. For example, an American College of Physicians website (www.doctorsforadults.com) highlights the fact that one in six adult visits to physicians are for sore throats and that when a physician uses a rapid test (with a throat swab), the 75% inappropriate antibiotic prescription rate for adults' sore throats is greatly reduced. (2)