“Cutting off the fat whilst keeping the flesh”


Reducing inappropriate or unnecessary testing is generally a good idea. Not only does it free up finances which can then be used on other more useful tests, it also improves the positive predictive value of the test in question by increasing the prevalence in the tested population.

But how exactly do you reduce inappropriate testing? Well you can look at guidelines from other centres or research papers published in journals. But in my opinion the best evidence to support reducing inappropriate or unnecessary testing is to collect your own localised data. This is particularly the case if you want to reduce unnecessary testing by introducing specific testing criteria based on certain patient or laboratory parameters.

For example if you want to restrict Hepatitis A testing to those patients with a significant ALT increase, then you need to look at the range of ALT values for all your patients with a genuine positive Hepatitis A result.

If you want to restrict Trichomonas testing to all those patients under a certain age, then you need to examine the age related prevalence rates for Trichomonas in your particular population.

The risk with cutting off the fat however is that you always risk cutting off a little bit of the flesh, i.e. you may miss the occasional positive where the patient has fallen outside the pre-determined testing criteria for that particular infection.

The key is in deciding whether the criteria or the cut-off level for testing that you have set are acceptable, and to do this you need to take into account as a minimum the severity of disease, the consequences of a missed diagnosis, the opportunity/potential to make the diagnosis at a later date. This is why you would never dream of restricting testing for syphilis in community age groups over a certain age, just because the prevalence in this cohort is so low. Because if you miss the diagnosis of syphilis the consequences could be a lot worse than if you missed a trichomonas infection…..

But possibly the most important factor to take into account when trying to adopt selective testing criteria is to consult with and gain approval from requestors, and in particular specialists in that particular area of testing. Thus it is a good idea to have good working relationships with the Infectious Diseases department and for that matter all your other users as well.

The requestors generally understand the situation. they will often be budget holders in their particular area/institution and understand exactly what you are trying to achieve. If you are reasonable, rational and communicative, only rarely will they stand in the way of what you are trying to achieve.

And the flesh and fat analogy works well in my opinion. If you try to cut off too much fat, then you will start removing the flesh as well, and you will only end up hurting the patient….



2 thoughts on ““Cutting off the fat whilst keeping the flesh”

  1. Totally agree Michael. Let’s do a retrospective study where we look at the Trich testing vs. positive rate, taking into account also ethnicity and symptoms on top of age. Hep A: your proposal makes sense for HAV IgM – don’t test for them if the LFTs are normal. HAV IgG, on the other hand, need to be tested in at-risk populations such as gay men to ascertain the immunity status.
    Hep B: how many repeat tests, often only a few weeks apart, do you get to check for the HBsAb levels? Does it make any sense?

    1. The relationship between trichomonas and ethnicity would be an interesting one to look at Massimo. I might have an “informal” look in the first instance.

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