Doctors won’t tell you what about your blood test?


There are various types of blood tests; liver function test, iron tests, thyroid function tests, serology and many more. However, the most common tests which people undertake are the complete blood count, shortened as CBC, and basic metabolic panel, done to check your infections, heart problem, kidney problem and even cancer! We all get blood tests done every now and then but there are certain things we may not know about them. Chances are your doctor hasn’t told these to you either. So, here we list seven things you may not know about a blood test.

‘NORMAL’ DIFFERS FOR MEN AND WOMEN: We all are fighting for gender equality but our biology is and always has been sexist. There is a difference in the way ‘normal’ reads for men and women. For example, normal haemoglobin range for men is 13.8 to 17.2 g/dL while for women it is 12.1 to 15.1 g/dL. Now your ideal range before you make an assertion.

‘NORMAL’ MAY NOT VARY WITH AGE: There are certain tests for which the ‘normal’ range can change with age, such as that of haemoglobin. The normal blood pressure range also changes with age. However, tests such as LDL cholesterol do not change with age. It should be lesser than 100 mg/dL for all ages.

POSITIVE RESULT MAY BE NEGATIVE NEWS: In a lot of tests like HIV, hepatitis C, or sickle cell anemia test, positive results refer to the presence of the diseases causing agents. In such situations, a positive result means the presence of the disease.

NEGATIVE RESULT MAY BE POSITIVE NEWS: Similarly, a negative test result will indicate the absence of disease causing agents in the blood in such diseases.

FALSE REPORTS ARE ABSOLUTELY POSSIBLE: There are many diseases the test for which depend on factors that are also influenced by other condition in the body. For example, a test for HIV can come falsely positive despite the person having the infection. This usually happens because the HIV test measures antibodies in the blood. If, let’s say, the person has other immune conditions such as rheumatoid arthritis, his test results can be false. Similarly, false negatives are also possible specially in the initial stages of the infection.

RESULTS MAY NOT ALWAYS INDICATE A DISEASE: The results from a test which indicate something wrong may not always indicate a disease. It could be due to many other factors, such as being on some medication, drinking alcohol the night before the test, or eating something specific you were not supposed to eat before the test. Such factors can also tweak your result. It is best to ask your doctor about any such risk factors in advance.

VALUES WILL DIFFER FROM LAB TO LAB: The test values are likely to differ if you get yourself checked from different diagnostic labs. This is because each lab has its own set of normal range against which your sample is compared. So, don’t just rely on one lab’s reports. If you have a doubt, change your lab.

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