The cost of capacity: MRI

If doctors are to be credible they must not only say what they want to do for patients and why, but they must employ economic arguments as well as medical ones to make their case.

Take MRI. It’s an amazing modality of investigation, not least to those of us old enough to remember neurology and oncology pre-MRI, when one relied on careful physical examination, intuition and guesswork, with a bit of diagnostic surgery thrown in. No longer the risky and inexact myelogram for diagnosing disc prolapses, just a quick if claustrophobic run through a magnet.

So our dear government decided to get in on the act. If MRI is good then everyone should have one whenever they want. For anything. Bit of backache, neck pain, knee pain, whatever. But the hospital waits are too long! So let’s provide scanners all over the place – in large general practices, polyclinics, allow access to private scans…

Wait a mo. Let’s look briefly at the medical issues and principles. We should do a scan if it’s likely to change our management. If a patient has back pain then (a) it is likely to get better within 6 weeks (b) a scan in a patient without root compression signs is unlikely to be helpful in planning treatment (c) a minor abnormality (eg a disc bulge) may be quite immaterial but may alarm the patient and (d) if the patient then goes to a specialist who cannot see the scan itself it wastes time. Indeed what is the process of radiological investigation? It is as follows:

Patient develops symptoms

  • Patient goes to GP
  • GP fixes X-ray or scan, writing brief and usually unhelpful clinical details on the request form (sometimes without taking a full history or examining the patient)
  • Radiologist looks at film with only half a sentence to go on and reports film accordingly (Question – ?fracture; answer: no fracture seen – never mind the other maybe important things such as arthritis, deformity).
  • GP tells patient investigation is normal
  • Patient still has symptoms

It’s actually a game of Chinese Whispers unless the clinician can see the film and interpret it (which many non-radiologists cannot anyway) in the light of the considerable clinical background.

But I ramble. Let’s suppose a hospital MRI unit is open 9 to 5 and has a waiting time of 12 weeks. The cost of reducing that to zero is the cost of staffing it from 7 to 9 – six hours of radiographer cover as overtime daily, which equates to perhaps £90,000 per annum. Now consider the cost of providing a new scanner “in the community” – capital cost £1.5-2m, revenue consequence 10% annual capital writedown, staff costs (at least 4 radiographers to cover, plus cost of radiologists’ time). At an annual cost of £200,000+ we now have two MRI scanners, neither of which will have enough business to work at full capacity. Or the Primary Care Trust contracts with a private scanner on a fixed contract basis and pays for more scans than it needs (many of which are not necessary) but is happy because it is doing the contracting rather than leaving scan decisions to expensive specialists. This is not cost-effective. Specialists don’t do scans because patients want them and do do them because the result may alter management. So we are cheaper. Why is this not obvious?

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