Inside a Lab Image
By Zuzanna K. Filutowska - Own work, CC BY-SA 3.0,
Este artigo foi revisto pela última vez em
Este artigo foi modificado pela última vez em 25 de Agosto de 2017.

Ao acionar um interruptor, as luzes se acendem. Ao abrir uma torneira, você pode lavar as mãos. Deixe alguém espetá-lo com uma agulha - ou dê algo de seu corpo a alguém - e obtenha informações sobre sua saúde.

É assim que os testes de laboratório têm sido vistos até recentemente. Exceto pelo seu contato com o profissional que colhe a sua amostra, é raro conseguir saber quantas pessoas estão envolvidas na geração de um resultado de teste de laboratório. Você também não encontra muitas oportunidades de aprender o que acontece após a amostra desaparecer de sua vista.

Como os laboratórios assumem um papel cada vez mais importante na área da saúde, a compreensão do que ocorre nos bastidores é quase tão importante quanto saber o que pode ser aprendido com os resultados dos testes. Os artigos abaixo foram elaborados para explicar um pouco mais sobre o laboratório e como ele funciona.

Accordion Title
Onde os exames laboratoriais são feitos 
  • Uma visão dos ambientes em que são feitos os exames laboratoriais.

    Today, laboratory testing is performed in many different settings – from the large reference lab that performs complex kinds of tests to your own home, where you might do a pregnancy test or monitor your blood glucose levels.

    Many of us, however, may wonder where our tests actually are performed. As we learn to take a more active role in our medical care, a clear understanding of what happens when our blood or urine specimens are sent “off to the lab” will help us to become more knowledgeable participants in our own health care.

    All labs are not the same for the simple reason that not all tests are the same. Just as tests vary in complexity, so too do labs vary in complexity, the volume of tests performed, the technology utilized, and the number and type of professionals who conduct the testing.

    There are important differences among the various testing settings. This information should be useful in understanding the variety of laboratory testing available.

  • Hospital lab

    In a Hospital Laboratory

    Almost all hospitals contain a laboratory, which is usually proportionate in size to the population it serves. Tests that are performed include those needed in emergency situations (e.g., markers for heart attack such as CKmyoglobintroponin), tests where results are needed rapidly for patient care (stat testing), and those done in high enough volume to warrant acquisition of the necessary equipment. Hospital labs are generally used by all of the inpatients at the particular hospital and by many outpatients who are being seen by physicians with offices offices affiliated with the hospital. However, as a patient, you may never actually visit the hospital’s laboratory unless you are sent there for your sample collection.

    Hospital labs may be segmented by type of testing, staffed by personnel trained in particular specialties. For example, there may be sections that focus on microbiology, hematology, chemistry, and blood banking. Other units may perform electron microscopy and immunohistochemistry tests, and still others can focus on surgical pathology, cytology, and autopsy. Some types of tests are sent to reference laboratories (see next page), which are more specialized, especially if the demand for them is low within the hospital.


  • Reference Lab

    At an Independent Clinical (“Reference”) Laboratory

    Reference labs are usually private, commercial facilities that do high volume routine and specialty testing. Most of the tests performed are referred from physician’s offices, hospitals and other health care facilities (e.g., nursing homes and other facilities). While most hospitals try to do as many tests as possible in-house, reference labs are used for specialized tests that are ordered only occasionally or that require specialized equipment.

    Since reference labs are usually some distance away, you may never step into a reference lab – unless you visit one of their phlebotomy stations to have your blood drawn – although you probably have heard of them. Many employee health insurance plans require that you use a specific lab, which is often indicated on your insurance card.

  • At Point of Care

    At the Point of Care

    Laboratory tests may also be performed at the point of care (POC) – in other words, at or near the site of patient care rather than in a distant laboratory. Doctors’ offices and clinics sometimes perform testing in the office, and hospitals may perform specific tests at the patient’s bedside.

    Labs within physician offices and clinics are generally small in size and offer limited test menus. Medical assistants typically conduct the testing. You are likely to know and interact with the person taking your sample and conducting the tests in this setting. Laboratory tests at these locations are usually limited to simple tests.

    Most physician and clinic labs conduct only a limited amount of testing due to the expense of equipment, supplies, and personnel for the office and the relatively small number of daily samples. However, point of care testing provides rapid results and offers convenience.

    Point-of-care testing done directly at the patient’s bedside has been increasing due to technological advances that have introduced portable devices that are easy to use and can produce rapid results. Examples include blood glucose tests, blood gas monitoring systems, and whole blood analyzers for cardiac markers and blood clotting tests. Tests included in POC programs must comply with quality standards comparable to tests performed in central laboratories [see Lab Oversight article]. It is expected that POC testing will increase in frequency as new devices become available, in part because they provide immediate information to physicians, allowing for more timely medical treatment.


  • At Home

    More and more tests are being adapted for use at home as patients take on new responsibilities for their health care. Some of the more common home tests include pregnancy tests and ovulation predictors for women, blood glucose monitors for diabetics, fecal occult blood tests to screen for colorectal cancer, and prothrombin time tests to monitor appropriate dosage of blood-thinning medications. There are other tests that allow patients to collect samples at home that they then mail to a particular laboratory for analysis (for example, home HIV antibody tests and hepatitis C tests); some of these may require a doctor’s order.

    Home tests are available directly over-the-counter at pharmacies, over the Internet, by telephone, or by mail order. Some may require a prescription from a doctor. Home tests offer definite advantages, including convenience, privacy, and rapid results. However, consumers should be cautious when using home testing. For example, results can be inaccurate if the kit has not been stored properly, if the sample was not collected correctly, or if instructions were not followed. All home tests must be approved by the U.S. Food and Drug Administration (FDA). There are also companies selling unapproved home testing products, which may be unreliable – be sure that the test kit you buy is FDA-approved (a list of over-the-counter in vitro diagnostic devices is available at

    >For additional information on home testing, see our article With Home Testing, Consumers Take Charge of Their Health.

  • Through a Direct Access Laboratory

    Through a Direct Access Laboratory

    As with home testing, direct access testing (DAT) has been growing in popularity over the past few years. Currently, 34 states permit consumers to order their own lab tests – without a medical order from their health care provider. Also known as patient authorized testing, DAT is a reflection of Americans' focus on health and preventive medicine, offering the opportunity for patients to take a more active role in their own health care.

    In some respects, direct access testing has been around for some time. Over-the-counter home tests are a type of DAT since they do not require a prescription and can be bought and used at the consumer’s discretion. Now, the trend has expanded to include laboratories offering clinical tests at the patient’s request. In retail centers in Colorado, Montana, Missouri, Kansas, and Utah, patients can walk into a lab and request certain tests; wellness centers offer health screens and other lab tests; and free-standing and mobile testing facilities offer screening tests to the public, such as in grocery stores and pharmacies.

    Most DAT labs limit the availability of tests to simple, general health tests such as complete blood counts (CBC)cholesterol levelsthroat and urine culturesdiabetes screening (blood glucose tests), chemistry panelsPSA for prostate cancerthyroid testsHIV antibody testsblood typingpregnancy tests, and urine drug screens.

    Direct access testing may reduce costs for the patient by eliminating the expense of doctor’s office visits, providing vital information to patients who are concerned with a particular health problem or who may otherwise avoid testing due to inconvenience or concerns over anonymity. However, most insurance companies do not cover tests that are not ordered by a physician; therefore, you should expect to pay out-of-pocket for these services. In addition, labs providing DAT services  must provide consumers with reference ranges and some assistance in interpreting the results. However, you are not operating under the guidance of your physician, who may be better able to determine what tests you really need but also what the results of those tests mean in light of your specific clinical signssymptoms, and medical history.

Article Sources

NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.

American Association for Clinical Chemistry. Order Your Own Lab Tests without Direct Physician Access. Press Release, July 31, 2001. Available online at through

Schulze, Matthew. “25 Percent More States Allow Direct Access Testing.” Laboratory Medicine (American Society for Clinical Pathology). November 2001. [No longer available online.]

The College of American Pathologists (CAP). Commission on Laboratory Accreditation: Point of Care Testing Checklist. October 2001. [No longer available online.]

Jerry O’Connell, MD. Columbia Hospital for Women, Washington, DC (written communication).

Wisconsin State Journal. March 17, 2002.

Types of Clinical Labs ( [No longer available online.] [No longer available online.]