In depth
Psoriatic arthritis and blood tests
No blood test makes this diagnosis, and that's the thing worth saying before anything else. What decides it is the examination, the skin, the scans, and how likely the disease already is in somebody like you. Those four things together are what this page is about, rather than any one result.
What the research found.
One study assessed 1055 consecutive people presenting with joint pain in several joints. Each had a clinical examination, blood tests, ultrasound with power Doppler of both hands, and X-rays of hands and feet, and they were followed to a definitive diagnosis. Of the 1055, 88 ended with psoriatic arthritis, which is 8.3 percent.
One national study measured how common this disease is among Swedish adults aged 18 to 79 years. The crude prevalence in 2017 was 0.39 percent, and correcting for wrong labels brought that down to 0.34 percent. Other analyses ranged from 0.32 to 0.50 percent.
That group also measured how many new cases appear each year, and the mean annual incidence among Swedish adults from 2014 to 2016 was 21.77 per 100000 person-years. Correcting for wrong labels brought it to 17.41. Other analyses ranged from 15.78 to 28.83, and incidence peaked between ages 50 and 59.
One study compared 803 people with psoriatic arthritis in two European countries. In the Italian group the most common other conditions were high blood pressure at 45.1 percent, abnormal blood lipids at 38.6 percent, and obesity at 30.8 percent. In the Belgian group they were high cholesterol at 30.9 percent, obesity at 27 percent, and high blood pressure at 26.4 percent.
Scriffignano and colleagues, Clinical and Experimental Rheumatology, 2023
One population study compared 3161 people with psoriatic arthritis against matched controls. Type 2 diabetes came out at an odds ratio of 1.7, high cholesterol at 1.5, high blood pressure at 1.5, and obesity at 1.5. Several heart conditions were also commoner, and the differences held after adjusting for heart risk factors.
What the number means.
| Test | What it measures | How it performs here | What it can't do |
|---|---|---|---|
| Any single blood test | Varies by test | This site holds no source on how any of them performs in this disease | Make the diagnosis. No blood test here does |
| The whole work-up together | Examination, bloods, ultrasound, and X-rays | Of 1055 people with joint pain assessed that way, 8.3 percent had psoriatic arthritis | Be replaced by one result. All four parts were used |
| Background rate in the population | How common the disease is in adults | About 0.35 percent of Swedish adults aged 18 to 79 in 2017 | Be ignored when reading a result. It sets the starting point |
| Background rate in a joint pain clinic | How common it is among people with joint pain | 8.3 percent in that study of 1055 people | Apply to you without your own history beside it |
| Metabolic screening | Blood sugar, lipids, and blood pressure | Diabetes 1.7, cholesterol 1.5, blood pressure 1.5 against controls in 3161 people | Diagnose the arthritis. It checks what comes with it |
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 page a reader didn't come here for
Most people opening a labs page want to know which blood test settles it, and in psoriatic arthritis there isn't one. That's the honest answer, and it's worth giving before anything else. This site holds no source on how any individual blood test performs in this disease.
There's no figure here for rheumatoid factor, no figure for anti-CCP, and no figure for HLA-B27 or inflammation markers. That's an absence in our sources rather than proof no such evidence exists. It's on record for the physician review, and it hasn't been filled in with a guess of any kind.
What this page can give you instead is something more useful than any single test result. It can tell you what the whole work-up looks like, and how likely this diagnosis was before any test was ordered. Both of those tell you more than a number that has never been published.
The whole work-up, in one study
One study assessed 1055 consecutive people who came in with joint pain in several joints. That's a large group, and it's also an ordinary one. Each person had four things done, which were a clinical examination, blood tests, ultrasound with power Doppler of both hands, and X-rays of hands and feet.
Then the study followed them until a definitive diagnosis was reached. That last step counts, because it means the labeling didn't happen on the first visit. Of those 1055 people, 88 ended with a diagnosis of psoriatic arthritis, which is 8.3 percent, and it's the figure the rest of this page rests on.
What that 8.3 percent is worth
This is the most useful number here, and it usually gets left out. It says that among people with joint pain in several joints, roughly one in twelve turned out to have this. So eleven in twelve had a different answer, and that's the starting point every result gets read against.
Here's why that changes how a result reads. A given test result means something different depending on how likely the diagnosis was before the test was done. A team reading your results is weighing them against everything else about you, and that isn't a trick or a shortcut. It's the plain arithmetic of diagnosis, and a clinician who sees this every week is doing it whether they say so out loud or not.
How common the disease is
Two national studies from Sweden give the background figures here, and both of them are about Swedish adults. So read them as a picture of that population, and not of yours. The first measured prevalence in 2017 among adults aged 18 to 79.
The crude figure was 0.39 percent, and correcting for wrong labels brought it to 0.34 percent. Other analyses ranged from 0.32 to 0.50 percent. Its authors summarize the whole thing as around 0.35 percent, and prevalence was lower in men and lower in people with more education. Among those in recent contact with specialist rheumatology care it was 0.24 percent, and during 2017, 32 percent received a biologic or targeted synthetic drug.
The second study measured how many new cases appear, and the mean annual incidence from 2014 to 2016 was 21.77 per 100000 person-years. Correcting for misclassification brought it to 17.41. Other analyses ranged from 15.78 to 28.83, and incidence was slightly higher in women and lower in people with more than 12 years of education. It peaked between the ages of 50 and 59, and no clear rising or falling trend appeared across 2006 to 2018.
What the blood tests are for, then
If no blood test makes the diagnosis, it's fair to ask why so many get taken. There are two reasons, and both of them are real. The first is to look for other explanations, because eleven people in twelve with joint pain have something else. Some of those do appear on blood tests, which is why the tests get sent.
The second is to check what comes with this disease. One population study compared 3161 people with psoriatic arthritis against matched controls, where type 2 diabetes came out at an odds ratio of 1.7. High cholesterol, high blood pressure, and obesity all came out at 1.5. That study found several heart conditions commoner too, including ischemic heart disease, peripheral vascular disease, congestive heart failure, valvular heart disease, and cardiomyopathy.
Those differences held after adjusting for heart risk factors. One study of 803 people in two European countries puts numbers on how common these are. In the Italian group, high blood pressure reached 45.1 percent, abnormal blood lipids 38.6 percent, and obesity 30.8 percent. In the Belgian group it was high cholesterol at 30.9 percent, obesity at 27 percent, and high blood pressure at 26.4 percent.
So a blood sugar or a cholesterol result on your file isn't about your joints at all. It's about the things that come with this diagnosis. Those are worth watching in their own right, quite apart from the arthritis.
The scan
That study of 1055 people used ultrasound with power Doppler of both hands, and it used X-rays of hands and feet too. Both of those were read alongside the examination and the blood tests. It doesn't report how the ultrasound performed on its own, so what the scan contributed has never been published.
How often it changed an answer has never been published either, which is a second thing missing from the record. That's a real hole, and it's recorded for the physician review. A visible hole is more use to you than a confident sentence that has nothing behind it at all.
What to ask
Ask what the whole work-up is, because one test on its own won't answer it. The study here used four kinds of information, and it needed follow-up on top of all of them. Mention psoriasis anywhere on your body, and that includes your scalp and your nails, because that's part of what decides this, and it isn't a blood test.
Ask what your team is still waiting to see, because not one person in that study was labeled on the first visit. A diagnosis that takes time isn't a diagnosis being got wrong. Ask what the blood sugar, cholesterol, and blood pressure results are for, because they're tracking things that come with this disease. Knowing that is what makes those three results worth your attention at a rheumatology visit.
Common misconceptions.
Myth. There's a blood test for psoriatic arthritis.
Reality. There isn't one that makes the diagnosis, and this site holds no source on how any individual blood test performs here. One study assessed 1055 people with joint pain, using examination, blood tests, ultrasound of both hands, and X-rays all together. Then it followed every one of them to a definitive diagnosis. All four parts were used, because no single one of them settles it.
Myth. If my joints hurt in several places, it's probably this.
Reality. Usually it's something else, because one study followed 1055 consecutive people who came in with joint pain in several joints. Of those, 88 ended with psoriatic arthritis, which is 8.3 percent. So roughly eleven people in twelve got a different answer, and that's the starting point any result gets read against.
Myth. It's a rare disease.
Reality. The disease is uncommon rather than genuinely rare. One national study put the prevalence among Swedish adults aged 18 to 79 at about 0.35 percent in 2017, with analyses ranging from 0.32 to 0.50 percent. New cases appeared at about 21.77 per 100000 person-years, or 17.41 after correcting for wrong labels, and it peaked between ages 50 and 59.
Myth. The blood tests that get ordered are about the arthritis.
Reality. Some of them are about what comes with it, and one study of 3161 people found type 2 diabetes at an odds ratio of 1.7 against matched controls. High cholesterol, high blood pressure, and obesity each came out at 1.5, and several heart conditions were commoner too. Those differences held even after adjusting for the usual heart risk factors.
Myth. A normal result means I don't have it.
Reality. No result on this page can do that, because no blood test here makes or excludes the diagnosis. The study that got closest used four kinds of information together, and it still needed follow-up to reach a definitive answer. So a normal blood test is one piece of a picture rather than an all-clear.
Cautions specific to this condition.
- Ask what the whole work-up is, because one test on its own won't answer it. The study here used examination, bloods, ultrasound, and X-rays together.
- Mention psoriasis anywhere on your body. That includes the scalp and the nails. It's part of what decides this and it isn't a blood test.
- Expect blood sugar, lipids, and blood pressure to be checked. Those track this disease rather than diagnose it.
- Read a result against how likely the diagnosis was to start with. About one in twelve people arriving with joint pain in several joints had this in one study.
- This page gives no reference range and no threshold for any test. Our set holds no source on how any single test performs here.
- Ask your team what they're still waiting to see. In the study here, people were followed to a definitive diagnosis rather than labeled on day one.
Discuss any change with the rheumatologist who manages your care. Nothing here replaces that conversation.
Questions patients ask.
Is there a blood test for psoriatic arthritis?
There's no blood test here that makes the diagnosis. This site holds no source on how any individual blood test performs in this disease, so this page puts no figure on any of them. The study here used a clinical examination, blood tests, ultrasound of both hands, and X-rays of hands and feet, all together. All four of those parts turned out to be needed.
How likely is it if I have joint pain in several places?
There's one study that answers that question directly, and it assessed 1055 consecutive people presenting with joint pain in several joints. It followed every one of them to a definitive diagnosis, and 88 ended with psoriatic arthritis, which is 8.3 percent. So about one person in twelve had it and the other eleven had something else.
How common is the disease overall?
One national study put prevalence among Swedish adults aged 18 to 79 at 0.39 percent in 2017 alone. Correcting for wrong labels brought it to 0.34 percent, and other analyses ranged from 0.32 to 0.50 percent, with its authors summarizing the whole thing as around 0.35 percent. Prevalence was lower in men and lower in people with more education.
How many people get it each year?
The mean annual incidence among Swedish adults from 2014 to 2016 was 21.77 per 100000 person-years, and correcting for wrong labels brought it to 17.41. Other analyses ranged from 15.78 to 28.83. Incidence peaked between ages 50 and 59, and no clear trend appeared across 2006 to 2018.
Why does the background rate help?
Because a result means different things depending on where you start from. Take somebody with psoriasis, nail changes, and swollen fingers, where a given result means a good deal more than it would in somebody without any of that. A team reading your results is weighing them against how likely the diagnosis was beforehand.
What are the blood tests for, then?
Partly to look for other explanations, and partly to check what comes with this disease. One study of 3161 people found type 2 diabetes at 1.7 against controls, with cholesterol, blood pressure, and obesity each at 1.5. One study of 803 people found high blood pressure in 45.1 percent of an Italian group.
What does the scan add?
The study here used ultrasound with power Doppler of both hands, and X-rays of hands and feet too, alongside the examination and the bloods. It doesn't report how each part performed on its own, so what the scan contributed has never been published. That's a real hole in the evidence, and it's on record for the physician review.
References.
- Ruta S; Jaldin Cespedes R; Cuellar L et al. Psoriatic Arthritis: Differential Features at the Time of Clinical Presentation in a Large Cohort of Patients with Polyarthralgia. Eur J Rheumatol. 2023;10:12-17. 10.5152/eurjrheum.2022.22035Journal Article
- Exarchou S; Wallman JK; Di Giuseppe D et al. The National Prevalence of Clinically Diagnosed Psoriatic Arthritis in Sweden in 2017. J Rheumatol. 2023;50:781-788. 10.3899/jrheum.221139National register study estimating the prevalence of clinically diagnosed psoriatic arthritis among Swedish adults aged 18 to 79 alive on 31 December 2017
- Exarchou S; Di Giuseppe D; Klingberg E et al. Incidence of Clinically Diagnosed Psoriatic Arthritis in Sweden. J Rheumatol. 2025;52:38-46. 10.3899/jrheum.2024-0376National register study of adults in Sweden
- Scriffignano S; Lories R; Nzeusseu Toukap A et al. Cardiovascular comorbidities in psoriatic arthritis: epidemiology and risk factors in two different European populations. Clin Exp Rheumatol. 2023;41:1815-1822. 10.55563/clinexprheumatol/aovikaCross-sectional analysis of two longitudinal cohorts
- Kibari A; Cohen AD; Gazitt T et al. Cardiac and cardiovascular morbidities in patients with psoriatic arthritis: a population-based case control study. Clin Rheumatol. 2019;38:2069-2075. 10.1007/s10067-019-04528-yPopulation-based retrospective case-control study using Israel's largest health provider database from 2000 to 2013
- Lindström U; di Giuseppe D; Exarchou S et al. Methotrexate treatment in early psoriatic arthritis in comparison to rheumatoid arthritis: an observational nationwide study. RMD Open. 2023;9. 10.1136/rmdopen-2022-002883Observational nationwide study from Swedish national registers
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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