Lab results – notes on interpreting them

ESR – remember that the normal ESR range varies depending on someone’s age.  For men, upper ESR limit = AGE/2.  For women, upper ESR limit = (age+10)/2.  So, for a 90 year old women, an ESR of 40 is okay.

Fasting Blood glucose – no longer order this test. Instead, do HbA1C.   The only time when this is preferable over HbA1C is

  1. if you suspect a rapid onset of diabetes (because HbA1C will take a few weeks to climb up) – e.g. acutely unwell patient (symptoms, ketosis, weight loss).
  2. in children (because most will have type 1)
  3. the pregnant   (multiple factors make HbA1C lower in pregnancy and therefore unreliable).

Faecal Calprotectin – if you have a patient who you think might have either Irritable Bowel Syndrome or Inflammatory Bowel Disease, PLEASE do this test which (on top of the clinical picture) will help you differentiate whether it is inflammatory bowel disease or not.  Calprotectin indicates inflammatory bowel disease.

FBC – The four main indices you need to look at are i) Hb ii) WCC  iii) neutrophil count and iv) platelet count.  If any of WCC, neutrophils or platelets are low, please check that the patient is not on an anti-rheumatic DMARD.   If they are, speak to rheumatology about what to do next.   (DMARDs dampen the immune system, and together with a low WCC/neutrophils, can put the patient at risk of dying if they come into contact with general infections).    For patients on DMARDs, worry if WCC<4.0, or neutrophils <2.0 or platelets <140.

FSH – FSH varies markedly during the peri-menopause and single measures are unreliable.  There is often no need for FSH level to be undertaken if the woman’s symptoms are very suggestive of the menopause.  FSH levels may be helpful in confirming the menopause in later stages.  FSH levels of greater than 30 IU/L are generally considered to be in the postmenopausal range.   If the value is less than 30, you CANNOT say either way whether she is menopausal or not – you can only make a diagnosis if it is above 30 IU/L.  Levels should be tested when the woman is not taking oestrogen-based contraception or hormone replacement therapy (HRT).  FSH level should be taken on days 2-5 in those women who are still menstruating.  Women with suspected premature menopause (symptoms under the age of 40) or following a hysterectomy with ovarian conservation, should have more than one FSH level taken because of the implications of premature ovarian failure.

HbA1C

  • Non-Diabetic: 41 and below
  • Pre-Diabetes: 42-47
  • Diabetic: 48 and above

If a patient is not a known pre-diabetic but HbA1C is in the pre-diabetic range

  • Task the diabetic practice nurse to add to pre-diabetes register and call patient in to discuss what this means and the role of diet, exercise and weight control (i.e. lifestyle measures in an attempt to reverse it).
  • HbA1C will need checking yearly – make sure they are not going up – if they are, bring the patient in again to discuss; otherwise they will become diabetic.

If a patient is a known diabetic, and their routine HbA1C comes back within normal or pre-diabetic range, then you NEED TO DO SOMETHING.  Don’t be fooled that it is okay.

  • If they are a Type 2 Diabetic
    • If  follow-up HbA1C is 41 or below, it’s likely their diabetes has resolved in which case – which is excellent.  Send a task to inform our diabetic nurse who will then decide whether the code needs to stay on or off and what the routine follow up will be thereafter.
    • If the HbA1c is 42-47, whilst not perfect, they are in good control.
    • If HbA1C is 48 or more, need better control – re-emphasise lifestyle measures and add/tweak tablets.
  • For a Type 1 Diabetic stable on insulin, for good control one would expect a HBA1C above the upper normal range.
    • If the HbA1C comes back within normal OR pre-diabetic range, it is likely they are having hypos.
    • So book for them to come in for a review with the doctor and the insulin dose will need changing if they are indeed having hypos.

H Pylori test: At Ashcroft, we do the Faecal H Pylori Antigen test.

Random Blood Sugar – again, not to use for routine Diabetic monitoring.  However, may want to do this

  1. in rapid onset diabetes or
  2. in children you suspect might have diabetes (which will usually be type 1) or
  3. those with gestational diabetes.
  4. if you suspect DKA.

Thyroid Function Tests – for patients already on thyroxine replacement, use TSH to determine whether the thyroxine dose needs altering or not.  Ideally, aim for TSH within range.    If a change in dosage needs to be made, it can take 2-3 months for things to stabilise.  So don’t repeat the TSH until 3m after the dosage change (and only request TSH, not T3 or T4 levels).

Urine dipstick – if there is microscopic haematuria – repeat later on.  If persistent, refer for cystoscopy and do the work up for the microscopic haematuria pathway.