A 67 year old woman had an unexplained Hb of 65 g/L. The only previous Hb result was 103 g/L from over four years ago. She felt generally tired with achy muscles most of the day for the past few months. An ESR had been sent, and came back as 110.

Q. Arrgh! PMR! Myeloma! Anaemia of chronic (rheumatological disease) of some kind!

A. Possibly. But it’s still quite likely that the ESR is a result of the anaemia, which raises the Rate at which Erythrocyte Sedimentate (sedimentate is totally a word).

Q. Dammit. We can only use CRP in these situations reliably.

A. You could measure plasma viscosity directly instead of ESR. This is expensive and not done in the NHS generally, and anyway you don’t usually need to unless you are a rheumatologist. And if you are, you probably know more about the merits of CRP vs ESR vs PV than me so I’ll shut up.

Q. Is this your shortest post yet?

A. Yes.

Q. Why?

A. Because if you can’t get a reliable ESR result, it doesn’t matter. Most of the conditions which benefit from ESR over CRP can be reviewed by a rheumatologist later. The only emergency where an ESR changes management is GCA; if you suspect this in a patient with an unreliable ESR, you can discuss with an on-call rheumatologist or treat now and await the formal biopsy.