Laboratory tests are an important part of modern diagnosis. They have an important advantage over history taking and physical examination: laboratory tests are relatively objective. That means that the results of the test usually do not depend upon who does the test. If many different technologists perform the same test with the same equipment, they should all get the same result. History taking and physical examination are more subjective: a lot depends on the knowledge, skill and attitudes of the person performing these procedures.

Despite their advantages, laboratory tests are not infallible. They will sometimes give false-positive or false-negative results. For example, sometimes a patient`s blood sugar will be elevated, and the doctor might think that the patient has diabetes when they are actually quite healthy. This would be a false-positive result. On the other hand, for example, a test for HIV or hepatitis might not show any sign of antibodies in the early stages of infection, and a patient might think that they are free of disease even though they are actually infected. This is would be a false- negative result.

Because laboratory tests sometimes give false results, it is important not to perform too many tests. The more tests you perform, the more likely you are to get a false result. Also, some laboratory tests involve a risk to the patient. Therefore, laboratory tests should not be performed as a first step to search for a disease. First, there must be a working diagnosis, usually from the history and physical examination. Then the laboratory test is used to confirm or refute that diagnosis.

Most often, laboratory tests involve taking some body fluid from the patient: blood, urine etc. This is likely to be somewhat unpleasant for the patient. Therefore, a friendly but professional manner is very important. This builds the patient`s confidence and calms their fears.

Because of the high and growing prevalence of serious diseases that are spread by body fluids, for example AIDS and hepatitis, it is very important to use safe techniques when performing tests. In a busy clinic, it is easy to become complacent about infectious diseases. The lab technologist has to be on guard constantly to protect both themselves and their patients.

Situation 1: A middle-aged woman with joint pain and fever is having blood drawn by a laboratory technologist.

Technologist: Mrs. Park, can you role up your sleeve and rest your arm on the table here.

Mrs. Park: Is that okay? (She follows the technologist instructions.)

Technologist: That`s fine. I'm just going to draw a little blood. This will only take a minute. Can you make a fist. (The patient makes a fist and the technologist ties a band around the patient`s biceps muscle.) Okay, you can open your hand.

Mrs. Park: How long will it take to get the results?

Technologist: If they are not busy in the lab, some of the results will be back tomorrow. Now, this will sting a little bit. (The technologist inserts a needle in the median cubital vein.)

Mrs. Park: That`s okay. I just want to know what`s wrong with me.

Technologist: Now, don`t move. I want to get another vial. (The technologist changes vials and continues to collect blood.)

Mrs. Park: How many of those are you taking? (Referring to the vials of blood)

Technologist: Just three. We have to collect the blood in different vials for different tests. Are you feeling okay?

Mrs. Park: Sure, I`m fine.

Technologist: All done. (The technologist draws out the needle and puts a piece of cotton over the vein.) Can you just hold this cotton in place for a minute.

Mrs. Park: That was easy enough. You`re very good!

Technologist: Thanks. Okay, I will just put a band-aid on your arm. You can take that off tonight or leave it on until tomorrow.

Mrs. Park: Can I take a bath tonight?

Technologist: Oh sure. That should be no problem at all. Now, your doctor`s office should give you a call as soon as they get the results.

Patterns:

* Can you
... role up your sleeve
... rest your arm on the table
... make a fist
... hold this cotton in place

* You can
* ... open your hand
* ... take that off tonight
* ... leave it on until tomorrow

* This will
... only take a minute
... sting a little bit

* The results will ... be back tomorrow
* I will ... just put a band-aid on your arm

* That should
... be no problem
* Your doctor`s office should
... give you a call

* I just want to
... know what is wrong with me
* I want to
... get another vial

* I`m just going to
... draw ... a little blood
* We have to
... collect ... the blood

Discussion:

1. In situation 1, the patient seems to be quite interested in getting the test results as soon as possible. Explain what you think is behind her concern about waiting for the results.

2. Why does blood for different tests have to be collected in different tubes?

3. What are some concerns that a patient might have about giving blood for tests?

4. What diseases of patients present a significant risk to laboratory personnel?

5. How can laboratory personnel protect themselves against infection from patient specimens?