Blood Test Interpretation

Blood Test Interpretation FI
I see many patients who have been told their blood test results are ‘normal’ and when analysing them I find this is often not the case.  This can be for a number of reasons outlined below.

I see many patients who have been told their blood test results are ‘normal’ and when analysing these result I find this is often not the case.  This can be for a number of reasons outlined below.

Conventional healthcare workers do not receive training in advanced interpretation of lab results at their respective training schools.  Additional training is available but most conventional practitioners don’t have the time to undertake or an awareness of the importance of advanced blood test interpretation.  Added to this is the pressure that most conventional practitioners are under in terms of limited appointment times and constraints by district health boards to limit testing.

These constraints have led to more and more tests becoming unfunded by district health boards (DHBs) over time.  I estimate about 40% of the tests that I used to be able to order funded when I first started as a GP are now unfunded.  This means that patients must pay for these tests, with many not being able to afford them.  Which particular tests are unfunded varies among the different DHBs, but usually include things like zinc, cortisol, FT3 (the active version of thyroid hormone) and Magnesium, etc.  It is therefore inappropriate to tell a patient that their lab results are ‘normal’ when not enough items have been tested.

Some examples of why I would look to do these unfunded tests are listed below (along with supporting links):

Other reasons patients may be inappropriately told their results are ‘normal’ is because they are not being interpreted accurately.  For example, I often see patients with TSH (a hormone from the brain that ‘tells’ the thyroid gland to make thyroid hormone) levels of 4-6 who have been told that is ‘normal’.  All test results are sent to the ordering practitioner along with a reference range.  Most countries reference ranges for TSH are around 0.4-4.

However, the guidelines that GPs in New Zealand (NZ) follow state that for TSH of 4-6 GPs can just ‘monitor every 6 to 12 months’ for ‘sublinical hypothyroidism’.  Subclinical hypothyroidism is defined as hypothyroidism with no symptoms but generally this blood test is not ordered unless a patient has symptoms (usually hypothyroid symptoms).

Another reason that patients are told blood tests are ‘normal’ is that the test itself is not the best test.  For example, NZ blood fat testing is called an umbrella term of ‘lipids’ or ‘cholesterol’ and includes Total Cholesterol, Triglycerides, LDL, and HDL.  LDL is inappropriately labelled ‘bad’ fat and HDL ‘good’ fat.  However, both LDL and HDL contain sub-fractions of which some are ‘good’ for us, and some are ‘bad’ for us.

‘Lipids’ are usually tested to give people an idea of cardiovascular risk, i.e. risk of ‘heart attacks’ and ‘strokes’.  However, more accurate ways of assessing this risk is to test lipoprotein a, homocysteine, or cholesterol sub-fractions, etc.  Unfortunately, whilst they are available, none of these three tests are currently funded in NZ.

More advanced testing is available but most of this is performed overseas.  There is certainly no DHB funding for these tests and they can run into 100’s of dollars for each panel.  However, each panel usually contains 100’s of individual results with an example being urine and saliva hormone testing panels.  This makes each result around about $1.50 each.  Compared to zinc at a NZ lab for example which costs about $40, these overseas test actually work out better value for the most part.

Whilst there is of course controversy about the interpretation of blood testing, one thing is for sure, don’t give up pursuing an answer for your symptoms if you are told your blood tests are ‘normal’.

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