ESR (sedimentation rate)

Red blood cells normally repel each other and sink only slowly in a standing tube. With inflammation that changes. Your liver then makes extra proteins, especially fibrinogen, and your immune system makes extra antibodies, and those proteins cancel the repulsion: the cells stack like rolls of coins and sink as clumps much faster than as single cells. The sedimentation rate measures that speed, in millimetres per hour. It is an indirect measurement: not the inflammation itself, but how much sticky protein is circulating in your blood. Those proteins come and go slowly. Fibrinogen has a half-life of days, antibodies of weeks, and that is why the sedimentation rate only rises days after the start of an inflammation and stays raised for weeks after recovery. CRP, which rises within hours and falls within days, tells what is happening now; the sedimentation rate tells what has happened in the past weeks. It also rises without inflammation: with age, because the proteins in your blood change, in women, with anaemia, because fewer cells sink faster, and in pregnancy. Your report shows the sedimentation rate in mm/hour. Normal for a man up to age 50 is about 1 to 10 mm/hour and for a woman up to age 50 1 to 15 mm/hour, where the labs overlap; from age 50 the band runs to 15 mm/hour for a man and to 20 mm/hour for a woman.

The sedimentation rate is the broad, slow gauge of inflammation, and exactly that slowness makes it useful. Anyone who has had vague symptoms for weeks, is tired, losing weight, has painful joints or muscles, and a CRP that is only slightly raised, sees in a high sedimentation rate that something has been going on for a while. In inflammatory rheumatism, in an inflammation of the blood vessels in older people that gives headache and stiff shoulders, and in some infections that run insidiously, the sedimentation rate is higher than the CRP suggests, and that difference is a clue in itself. A second reason is that the sedimentation rate measures antibodies. With a proliferation of antibody cells in the bone marrow, which occurs mainly over sixty, the blood fills with one type of antibody, and the sedimentation rate rises to far above a hundred while CRP can be normal. A sedimentation rate that high without an infection, certainly with anaemia, bone pain or a kidney working less well, is the reason to look at that. For anyone who is healthy and feels well, the sedimentation rate is mainly a value to see low and then leave alone. It says nothing about vascular risk that CRP does not say better, it rises by itself with the years, and a slightly raised value without symptoms and with a normal CRP is, in a woman over fifty, usually just her age.

A low sedimentation rate is healthy, and there is no lower limit that means anything. A value at the bottom of the scale means there has been no inflammation of note in the past weeks and that the proteins in your blood are normal. That is the outcome you want. A high sedimentation rate means there is more sticky protein in your blood, and the question is why. In order of how often it occurs: an inflammation or infection that has been running a while, from an inflamed joint to pneumonia or an inflammation in the gut; anaemia, in which fewer cells sink faster; a pregnancy, in which the sedimentation rate naturally rises; and your age, because over fifty the band sits higher for everyone and highest in a woman. A sedimentation rate above a hundred is a different story: it fits a severe infection, an inflammation of the blood vessels, a proliferation of antibody cells or a malignancy, and it should be investigated the same week, even without clear symptoms. Always read the sedimentation rate beside CRP, because the two move on a different timescale and the difference between the two is a clue in itself, beside haemoglobin, because anaemia lifts it without inflammation, and beside your age and sex, which determine which band applies to you.