What Do Lab Tests Really Mean?

You're at the doctor's office because you think something might be wrong. Rationally, you know tests are probably necessary, but getting the tests done sometimes provokes a lot of anxiety in all of us. We want to know the results, but are very concerned about the outcome."You need blood work" your doctor remarks casually. Your insides do an immediate flip-flop and you feel as if you've just begun hurtling down a very steep roller-coaster.

And when the results come back, it's tough to understand the medical jargon, particularly if the tests are "positive". We've all had the experience of "going south" and not listening to another word that's said after the initial "your test results are positive". Our minds are racing ahead, imagining all the awful possibilities.

Rarely, a considerate physician will be able to put the lab results in a less-worrisome perspective for the patient. For patients, it's important to know some key facts - facts that will empower you any time you need lab tests done.

First, statistically one out of every 20 tests performed will be reported as "abnormal" - even though the result is "normal" for the person being tested. If you are perfectly healthy and have 20 tests done on your blood sample, one of those 20 test results will be "out of the normal range" based on statistics alone.1

This is because a normal test range is calculated by eliminating the top 2.5% and the bottom 2.5% of results for a large group of normal people. This leaves the "normal range" as 95%. So if 20 tests are done, statistically one will be "abnormal", because its results fall in the top or bottom 2.5%. The result is normal for you, but reported as "abnormal".

Other factors to consider are the sensitivity and specificity of the lab test.2 Sensitivity relates to the test's precision in detecting the disease when the disease is present. If a test for colon cancer was 90% sensitive, it would miss ten cases of the disease out of every 100 cases. Specificity relates to whether a positive test actually indicates the presence of the disease you're being tested for. If a test is 90% specific, in ten cases out of 100 positive results, the patient does not actually have the disease.

So if a test has low sensitivity, actual cases of the disease may be missed. If a test has low specificity, test results reporting the presence of the disease may be wrong. All these factors need to be considered in accurately interpreting test results. Things are not always as they seem.3

Bottom line - test results always need to be evaluated in the specific context of the patient. An isolated lab result - or set of results - needs to be related to the patient's condition and circumstances. An accurate diagnosis is not based on lab results alone. That could be a big mistake. Similarly, x-ray, ultrasound, or MRI results need to be interpreted in context also.
Trying to interpret an x-ray without any clinical information is likely to lead to a wrong conclusion. Context is everything. If you have questions, we will be able to explain why certain tests are necessary.

1Thomas SL, et al: How accurate are diagnoses for rheumatoid arthritis and juvenile idiopathic arthritis in the general practice research database? Arthritis Rheum 59(9):1314-1321, 2008
2Friston KJ, et al: Classical and Bayesian inference in neuroimaging: theory. Neuroimage 16(2):465-483, 2002
3Kobayashi M, et al: Intraindividual variation in total and percent free prostate-specific antigen levels in prostate cancer suspects. Urol Int 74(3):198-202, 2005

Rhode Island Chiropractic Pain Control Clinic
371 Broadway Providence RI 02909
Phone: 401-274-9355 Fax: 401-455-0446

1524 Atwood Avenue Johnston RI 02919
Phone: 401-274-9355 Fax: 401-455-0290

197 Taunton Avenue East Providence RI 02914
Phone: 401-435-4999 Fax: 401-434-7772

586 Dexter Street Central Falls RI 02863
Phone: 401-729-4500 Fax: 401-723-0008

Locations

Find us on the map

Office Hours

Our Regular Schedule

Johnston Office

Monday:

9:00 am-6:00 pm

Tuesday:

9:00 am-6:00 pm

Wednesday:

Closed

Thursday:

9:00 am-6:00 pm

Friday:

9:00 am-12:00 pm

Saturday:

Closed

Sunday:

Closed

Providence Office

Monday:

9:00 am-12:00 pm

Tuesday:

9:00 am-6:00 pm

Wednesday:

9:00 am-6:00 pm

Thursday:

9:00 am-6:00 pm

Friday:

9:00 am-12:00 pm

Saturday:

Closed

Sunday:

Closed

East Providence

Monday:

10:00 am-5:00 pm

Tuesday:

Closed

Wednesday:

10:00 am-5:00 pm

Thursday:

10:00 am-5:00 pm

Friday:

Closed

Saturday:

Closed

Sunday:

Closed

Central Falls

Monday:

12:00 pm-6:00 pm

Tuesday:

Closed

Wednesday:

12:00 pm-6:00 pm

Thursday:

Closed

Friday:

Closed

Saturday:

Closed

Sunday:

Closed

Testimonial

  • "A few months ago I suffered injuries as a result of a car accident. The Doctors and staff at Rhode Island Chiropractic were able to alleviate my lower back pain which allowed me to return to my normal daily activities. The Doctors and staff were very helpful and pleasant during this difficult time which made my path to recovery much less painful!"
    Scott, 48, Providence RI