Au/ml help

[AlmWales]

The range for intrinsic factor test result is any result below 1.21u/ml (negative )and above 1.53u/ml (positive). I was informed my result was 1.63. Yes, no measurements of u/ml.

When I asked for B12 injections (local GP Wales) as I believed I'd proved I was deficient by these tests coming back high ( lots of symptoms & neurological and family history) I was told the way the test was INTERPRETED has changed. It is now based on a scale 0-20 ?

Also, is there any difference in

Au/ml and U/ml. I have read something about the "A" standing for automic? And might be just the calibration of the machine?

Anyway, how can your test be measured in decimals? Either below or above? Wouldn't this make a positive test result unachievable? I would be grateful of any help regarding a simplistic explanation.

[topazrat]

Don't know if it helps, but my results said normal was Intrinsic factor antibody level 0 - 6.1 u/ml at my surgery. I've never heard of Au/ml. So, I'm probably not helping at all.

Mine was 30 at diagnosis..

[helvella]

AU = Arbitrary Units

U = IU = International Units

(At least, that is the usual meanings of those abbreviations/acronyms.)

Rather than me failing to explain, I'll put a Wiki link: en.wikipedia.org/wiki/Arbit...

The Reference Interval (RI) or range must go with the test. You can't just pick up a number from one test and evaluate it against another set of numbers. Sometimes units can be converted (like Celsius and Fahrenheit) but you can't take a number like 10 and see it as liquid water in C and ice in F.

Afraid I don't quite get your question about decimals. If you mean that they have simply given you a number with no reference interval and no units then that is NOT a result. It is just a number. You are entitled to your result and that MUST include whatever units and other information required for you to understand it.

[Gambit62 Administrator]

The range should be determined by the lab doing the testing. AU will obviously vary from lab to lab but IU can also vary depending on the kit and test methodology being used - though the amount of variation for some test may be minimal.

[FlipperTD]

Scientist, not medic. I did these tests in the dim and distant past.

u=units of activity. I= International [as in units]. As Helvella states below, AU = Arbitrary units, which roughly translates to 'When I use a word, it means what I intend it to mean, no more, no less.' So using 'AU' is a means of getting the number that comes out of the analyser into something that looks like an antibody unit. To define a test we need a standard for comparison, so we'd need an agreed reference preparation. Unless things have changed, there isn't one. So, every lab will that does the test will be reporting their own interpretation.

If it was Haemoglobin, that's easy because we know the structure and the Molecular Weight. Likewise Sodium, or Potassium. We know what they are. However, IFAb is different. Using a confusion of 'units' helps nobody [IMHO], because it's not possible to compare results between sites using different methods.

There is [or there was, and I'm sure it's not gone away] a UK National Scheme for IFAb. As part of the NEQAS(H) system. The National External Quality Assurance Scheme for Haematology. This provides laboratories with some comfort in knowing that their results can be compared with other labs, but this is for scientific purposes, not 'general consumption'.

My preference was to report results as 'Positive', 'Negative' or 'Equivocal, please repeat', and back that report up with further advice on when the repeat should be performed.

So, when 'u' is used in a report, I'd be tempted to ask 'Units of what, exactly?' I know that's easier for me than the patient. However, the claim that Interpretation has changed and '1-20' is shocking. The result from the lab has more credence than someone [who?] adding their different interpretation, because they may have 'borrowed' a range from another provider, and it's getting further and further away from the truth. Whatever 'truth' might be. I realise I've rambled here, but short of knowing exactly how the test has been performed, it's impossible to interpret the result.