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Getting Accurate Pathology Tests

We may think you go to the lab with your pathology request and the results obtained will be as informative as possible. But did you know that there are many variables to take into consideration to get the most accurate representation of what is going on in your body? Below is some useful considerations:

  1. Fasting or not? More tests are better when taking in a fasting state. Obvious things like glucose, homocysteine and cholesterol levels need to be taken fasting but other tests like bicarbonate levels (part of the urea and electrolyte test for kidney function), iron studies, zinc and copper can be influenced by food and alcohol intake. So if in doubt, do your tests fasting!
  2. Ensure the test is done at a representative time. If you want a general check up, don’t have bloods drawn when you are vomiting or have a current infection. The day of a women’s cycle is important not only for hormone measurements (e.g. progesterone should be measured one week after ovulation in pre-menopausal women), but things like zinc can decrease and copper increase in the post-ovulation phase and ESR can be affected by oestrogen levels.
  3. Be sure the results will reflect the reason you are doing the tests. If you are checking if your selenium levels have come up after supplementation after previously low results, you would stay on the supplements. However if you want to decide whether you are fine without them, you would cease taking them 5 days before the test.
  4. Beware of Lab errors, timing and collection problems. Lab staff are only human, and machines can make mistakes. Problems in the collection (e.g trauma to a vein, not spinning the blood down quickly enough) and machine errors do occur. If you get results that are completely at odds with  previously ones, or are unexpected of don’t make sense, you can ask for a retest. Labs keep the specimens for at least a week. Some tests are time sensitive due to instability of what they are testing for e.g. Pyrroles. This is best done in controlled collection centres where storage and transport are standardised.   If you have eaten a fatty meal, the fat in the blood (lipemia) can affect the accuracy of the results. This is the same if you have very high bilirubin levels (e.g. ‘icterus’ due to hepatitis or gall stones). If the blood has been hemolysed due to a lengthy or traumatic blood collection, this can lyse the red cells and make many results inaccurate (haemolysis increases potassium, magnesium, zinc and histamine readings,and can reduce bilirubin levels)
  5. Pre-collection behaviour. Exercise can influence results like liver function tests, inflammatory markers and cortisol levels. Stress and intercourse can change prolactin levels.  The time of the day the specimen is taken , diurnal rhythm  and shift work can affect results (e.g. of cortisol levels).
  6. Interactions. If the marker for iron storage (ferritin) is raised, it may indicate inflammation is occurring, and other markers e.g. ESR or CRP meed to be considered and tested for at the same time. Also look at the white cells as they can give clues as to an infection or response to inflammation.

Doreen Schwegler (BApSc. RMIT; DipApSc. SSNT) worked as a Laboratory Scientist in pathology labs for over 15 years years prior to working full time  as Naturopath and Fertility Specialist at All Degrees of Health in Essendon Melbourne.

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