Here are some tips about rational use of laboratory investigations which may be helpful not only for young doctors but also for the patients:
a . Plasma Glucose should be advised in fasting condition except in emergencies.
A Borderline result should be further investigated by Oral Glucose Tolerance Test (OGTT). Random glucose should not be advised in an otherwise normal person.
b . Fasting for lab test means no food or drink for the last 10-12 hours but plain water is allowed. In fact patient should be encouraged to take water according to the weather.
c . For estimation of Cholesterol and its fractions (Direct HDL-Cholesterol, Direct LDL-Cholesterol and Non-HDL-Cholesterol) fasting condition is not mandatory. Fasting for 10-12 hours is mandatory, however, for triglycerides estimation.
d . Serum ALT is a very sensitive marker of hepatocellular disease. So in a person without jaundice, only ALT may be advised instead of whole Liver Function Tests (LFT).
e . Only urea may be carried out for screening of renal dysfunction because there is no kidney disease with normal urea. In a patient with normal urea no further renal tests are required.
f . The list of Cardiac enzymes (or markers) has been changed in recent years.
AST and LDH has been excluded and now replaced by CK-MB and Troponins.
g . ‘TSH only’ is a well-known regimen for the screening of thyroid abnormalities.
T 3 and T 4 should be reserved for patients with abnormal TSH.
Some of these tests may be very trivial in cost but considering large number of patients who are advised, a significant amount may be saved or diverted to more useful investigations.