• Question: How do you handle uncertainty when you’re not 100% sure of a diagnosis?

    Asked by SaweraN on 5 Nov 2025.
    • Photo: Andrew Senior

      Andrew Senior answered on 5 Nov 2025:

      Uncertainty can’t be left to chance. So we set a standard. A standard is a red line where you say if a number is above this value, the answer is yes. If it is below this value, the answer is no. We set these benchmarks based on historic data and statistics. For example, a study may have been done where 99,999 out of 10,000 patients which had a reading above 80% were confirmed to have the disease. So we can say pretty confidently that if you get a reading above 80%, then you have identified the disease in this patient.

      It’s this tie between historical data and real-world tests that makes diagnoses reliable. But in genomics, there isn’t always enough historical data to give us a reliable benchmark. For example, we may find a mutation and we may be confident that we have correctly concluded it is there. But there are only a few studies around the world that have tied this mutation to a certain disease. This means we can’t create a reliable scoring system to classify our results as positive or negative. In these cases, we report the results as inconclusive or (what we call in genomics) as a VUS – a variant of unknown significance.

    • Photo: Melissa Upjohn

      Melissa Upjohn answered on 6 Nov 2025:

      Great question, it’s something we deal with often as a vet when trying to work out the best way to manage an animal’s welfare. I discuss with an owner what our options might be and we come to a joint decision as to what to do, based on the balance of the information which we have and the risks and benefits which go with the various options.
      As an example, if a dog is being sick, we have to work out whether this is something that will get better with a bit of time or whether we need to do something more specific to investigate/fix the problem. Perhaps the dog has eaten something which has has caused an upset in its stomach, but a day without food will allow the stomach to settle and the problem will resolve. Or perhaps the thing the dog has eaten something is causing a blockage which will only resolve if we do surgery to remove it and it would be potentially dangerous to ‘wait and see’ as the dog will become increasingly more unwell if we leave the thing in place and the chances of the dog surviving the surgery are lower if we do this when the dog is unwell. In this case, we might decide to take an X ray of the dog or do an ultrasound scan to try to get a better ‘picture’ of what’s going on inside the dog, before making a decision as to whether surgery is likely to be needed. Of course, the other thing to consider as a vet (rather than a doctor) is the cost of doing these things as there’s no NHS for animals so the owner’s situation regarding having money to pay for diagnostics/surgery is also something we have to take into consideration – a tricky balance to strike.

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