In depth
Vasculitis and blood tests
Twenty-three of 130 people with giant cell arteritis had both a normal sedimentation rate and a normal CRP. That is roughly one in six of them, in a disease where untreated inflammation threatens sight. So a normal pair of markers is not the thing to be reassured by, and that is what this page is about.
What the research found.
For spotting giant cell arteritis, CRP caught 74 percent of the cases and cleared 49 percent of the people who did not have it. Its area under the curve came out at 0.675. The sedimentation rate caught 48 percent of the cases, cleared 72 percent, and came out at 0.644.
Twenty-three of 130 giant cell arteritis patients had a normal pair, with a normal sedimentation rate and a normal CRP. Those measured later after their symptoms began were more likely to read normal. The two timings were a mean of 35 days against 20, at a P value of 0.03.
The usual age rule for the sedimentation rate has two forms, one for each sex. For men, take your age and halve it, and for women, add ten to your age first and then halve it. Applying that rule removed an apparent age difference in one group of patients.
One study covered 198 patients with polymyalgia rheumatica, giant cell arteritis, or another vasculitis. Neither the current glucocorticoid dose nor the total taken over time was associated with the lowest T-score. Three other things did, which were a lower body mass index, a past spine fracture, and taking a heartburn drug.
What the number means.
| Test | What it measures | How it performs in giant cell arteritis | What it can't do |
|---|---|---|---|
| CRP | A protein the liver makes in response to inflammation, moving within a day or two | 74 percent sensitive, 49 percent specific, area under the curve 0.675 | Exclude the diagnosis. It misses about a quarter of cases |
| ESR | How fast red cells settle, affected by inflammation, age, anemia, and pregnancy | 48 percent sensitive, 72 percent specific, area under the curve 0.644 | Exclude the diagnosis. It misses more than half of cases |
| Both together | The usual approach, since they measure different things | 23 of 130 patients with the disease had both normal | Guarantee anything. Roughly one in six had a normal pair |
| ESR, age-adjusted | The conventional limit rises with age | Age over two for men, age plus ten over two for women | Be applied without knowing the person's age and sex |
| ANCA | Antibodies defining a subgroup of these diseases | This site holds no source on its diagnostic performance | Be described here at all until a reference is supplied |
| Bone density | Not a marker of disease, and relevant on long-term steroids | Dose wasn't associated with the minimum T-score in 198 patients | Be predicted from your steroid dose alone |
A reference range is not a target. Where a range on this page differs from the one your laboratory prints, the difference is explained above and sourced below. Where no trial has tested a target, this page says so rather than offering one.
The finding that changes what happens to people
A 2025 study looked at how well the swelling markers spot giant cell arteritis, and one figure from it is worth taking into any appointment. Twenty-three of 130 patients with the disease had both a normal sedimentation rate and a normal CRP. That is roughly one in six of the people in that study.
The accuracy figures explain how that happens, and they are worth reading together. CRP caught 74 percent of cases and cleared 49 percent of healthy people, with an area under the curve of 0.675. ESR was 48 percent sensitive and 72 percent specific, at 0.644. A test that catches 48 percent misses more than half of what it is asked about.
Giant cell arteritis threatens sight, and untreated it can cause sudden and permanent visual loss. So the consequence is serious and the tests miss cases. The clinical picture outranks a normal number here, more clearly than it does anywhere else on this site.
Why the two markers disagree
CRP and ESR measure different things, which is why both get sent. CRP is a protein your liver makes when it gets swelling signals, and it moves within a day or two. ESR measures how fast red cells settle in a tube, and swelling affects that, along with your age, low blood counts, and pregnancy. It also moves a good deal more slowly.
Their accuracy figures follow directly from that difference, and the pair of them reads as a mirror image. CRP misses fewer cases and raises more false alarms. ESR raises fewer false alarms and misses more cases. Neither is the better test, and each covers part of what the other misses, which is why both get sent.
Age deserves its own note here, because the conventional limit for the sedimentation rate rises with it. The usual age rule has two forms, and both of them are simple arithmetic. For men, take your age and halve it, and for women, add ten to your age first and then halve it. In one group of patients, applying that rule removed an apparent age difference entirely, so a slightly raised ESR in an older person is not automatically meaningful.
The timing finding, which runs the wrong way
That study reported something most people would guess backwards. Patients measured later after their symptoms began were more likely to read normal than the ones measured early on. The two timings were a mean of 35 days against 20, and the P value was 0.03.
The intuition is that a longer illness ought to produce higher markers rather than lower ones, and that is not what came out. The study found the link running the other way around. This page reports the finding as it was found, and it offers no explanation for it, because nothing is on record.
The practical consequence is clear enough even without a mechanism to explain it. A normal marker several weeks into an illness gives less reassurance than the identical result at the start. The later one is also the point at which somebody might be tempted to relax, which is the trap.
The difference on this page worth naming
This site holds no source at all on ANCA testing. ANCA stands for antineutrophil cytoplasmic antibodies, and the test defines a whole subgroup of these diseases. Somebody with ANCA-associated vasculitis will come to a page like this one looking for it, and will not find it here. Naming that hole beats filling it with a guess.
How many cases an ANCA test catches is therefore not something this page can tell you. Neither is how many healthy people it clears, nor what a positive result should change, nor what a negative one rules out. Guessing at any of those is not on offer, because a plausible-sounding figure for a test that important is worse than an admitted hole.
If you have been quoted a figure, asking where it came from is reasonable. Holding the references yourself puts you in a position to fix this, which is not something a reader can usually do. Sending them is what would let this page cover the subject properly.
What to watch on long-term treatment
Bone density is not a marker of your vasculitis, and it is still the measurement most worth having on long-term steroids. Most people with systemic vasculitis are on them for a long stretch. The relationship between the dose and the bone is also less direct than most people expect it to be.
One study covered 198 patients with polymyalgia rheumatica, giant cell arteritis, or another vasculitis. Neither the current glucocorticoid dose nor the total taken over time was associated with the lowest T-score in them. Three other things were associated with lower bone density, and those were a lower body mass index, a past spine fracture, and taking a heartburn drug.
That study looked at people at one moment rather than following them, and most were already on bone protection. So it cannot show what a trial would show. Read carefully, it argues for bone protection and against predicting your risk from your dose alone.
The 2017 American College of Rheumatology guideline covers the rest of it. It makes a strong recommendation for anyone on long-term glucocorticoids, whatever the diagnosis behind them. Get your calcium and vitamin D right, take up weight-bearing and strength-building exercise, stop smoking, and limit alcohol.
Common misconceptions.
Myth. Normal inflammatory markers rule out giant cell arteritis.
Reality. Twenty-three of 130 patients with the disease had a normal sedimentation rate and a normal CRP together. CRP caught 74 percent of cases and the sedimentation rate caught 48 percent, so both miss cases and one misses more than half. Untreated giant cell arteritis threatens a person's sight. So a normal result is the wrong thing to be reassured by when the picture fits.
Myth. The sedimentation rate is the traditional and therefore better test.
Reality. CRP caught more cases, at 74 percent against 48 percent, with an area under the curve of 0.675 against 0.644. ESR was the more specific of the two, at 72 percent against 49 percent. They measure different things and they often disagree, which is why both get sent and why neither settles the question.
Myth. A normal marker weeks into the illness is reassuring.
Reality. It reassures less than an identical result early on, which goes against instinct and is what the study found. Patients measured later after their symptoms began were more likely to read normal. The two timings were a mean of 35 days against 20, at a P value of 0.03. A normal result late in a story does not hold the weight it would have held at the very start of it.
Myth. My steroid dose tells me my fracture risk.
Reality. One study covered 198 patients with these diagnoses, and neither of the two dose measures was associated with the lowest T-score in them. That held for the current steroid dose and for the total taken over time. Lower body mass index, prior vertebral fracture, and proton-pump inhibitor use were the three things that did. That study looked at people at one moment and most were already on bone protection, so it cannot replace a trial. What it does argue is that dose alone does not tell you the risk.
Questions patients ask.
Can I have giant cell arteritis with normal blood tests?
Yes, and it is probably the most consequential fact anywhere on this page. Twenty-three of 130 patients with the disease had both a normal sedimentation rate and a normal CRP. CRP caught 74 percent of cases and cleared 49 percent of healthy people, at an area under the curve of 0.675. The sedimentation rate caught 48 percent of cases and cleared 72 percent of healthy people. Because untreated disease threatens sight, normal markers are not the thing to be reassured by.
Which is the better test, CRP or ESR?
Neither, and the pair works better than either one alone. CRP catches more cases, at 74 percent against 48 percent, so it misses fewer. ESR clears more healthy people, at 72 percent against 49 percent, so it raises fewer false alarms. Areas under the curve were 0.675 and 0.644, and both describe a test that helps rather than one that decides. Disagreement between them is normal rather than a laboratory error, which is why both get sent and why reading them together is the point.
Why would my markers be normal if I'm unwell?
Timing is part of it, and the direction of the finding surprises people. Patients measured longer after their symptoms began were more likely to read normal, at a mean of 35 days against 20, with a P value of 0.03. So a normal result late in an illness reassures less, and an identical result at the start reassures more.
Does age change how I should read my ESR?
Yes, and the rule is simple enough to use on the back of an envelope. It has two forms, one for men and one for women. For men, take your age and halve it, and for women, add ten to your age first and then halve it. In one group of patients that rule removed an apparent age difference entirely, so a slightly raised ESR in an older person is not automatically odd.
What about ANCA testing?
This site holds no source on it, which is honest to admit and a large absence. ANCA defines a whole subgroup of these diseases, so leaving it out is not a small omission. How many cases it catches, how many healthy people it clears, and what a positive or negative result should change are all unanswered here. If somebody has quoted you a figure, asking where it came from is fair, and sending us a reference would let this page cover it properly.
Should my markers be checked to follow my disease?
They get used that way in practice, and this site holds no source on how well they do it. Nothing we hold covers monitoring rather than diagnosis, and those are different questions. A test can be good at one of them and poor at the other. What the diagnostic data does establish is that a normal marker does not mean the disease is absent, which is worth taking into any talk about a reassuring result.
What about my bones on long-term steroids?
Bone density is not a marker of your vasculitis, and it is still the test most worth having on long-term treatment. One study covered 198 patients with these diagnoses, and neither dose measure was associated with a low T-score. The three things that were associated with a low T-score were a lower body mass index, a past spine fracture, and taking a heartburn drug. So that argues for bone protection and against reading your risk off your dose.
References.
- Currier C; Bays A; Thomason J. Normal inflammatory markers in giant cell arteritis: a diagnostic blind spot. Rheumatology International. 2025;45. 10.1007/s00296-025-05930-3Retrospective diagnostic accuracy study within a single fast-track GCA clinic
- Ranganath VK; Elashoff DA; Khanna D et al. Age adjustment corrects for apparent differences in erythrocyte sedimentation rate and C-reactive protein values at the onset of seropositive rheumatoid arthritis in younger and older patients. The Journal of rheumatology. 2005;32:1040-2. PMID 15940764Observational cohort analysis of 263 patients with early seropositive RA enrolled within 14 months of symptom onset
- Palmowski A; Wiebe E; Muche B et al. Glucocorticoids Are Not Associated with Bone Mineral Density in Patients with Polymyalgia Rheumatica, Giant Cell Arteritis and Other Vasculitides—Cross-Sectional Baseline Analysis of the Prospective Rh-GIOP Cohort. Cells. 2022;11:536. 10.3390/cells11030536Cross-sectional baseline analysis of a prospective cohort
- Buckley L; Guyatt G; Fink H et al. 2017 American College of Rheumatology Guideline for the Prevention and Treatment of Glucocorticoid‐Induced Osteoporosis. Arthritis & Rheumatology. 2017;69:1521-1537. 10.1002/art.40137GRADE-based clinical practice guideline
This page gathers the published research on this subject into one place. The studies behind it were published between 1989 and 2026, and every figure links to the paper it came from. Those studies were peer reviewed. This summary of them was not. Dr. Sarah Luebker is reviewing these pages one at a time and has not reached this one yet, so it carries no medical review date and nothing here is her opinion or her advice to you. Each page gets updated as she reaches it. It is here in the meantime because the science is worth having in one organized place that is easy to find and easy to read. Talk to your own clinician before acting on any of it.
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