Lab reference
ANA
What the research found.
One study tested blood from apparently healthy people at four dilutions. At 1 to 40, 31.7 percent were positive, and at 1 to 80 it was 13.3 percent. At 1 to 160 it was 5.0 percent, and at 1 to 320 it was 3.3 percent.
One study tested 4,754 Americans chosen to stand for the whole country, using a single dilution of 1 to 80. It found 13.8 percent positive. Scaled up to the population, that works out to more than 32 million people, hardly any of whom have lupus.
One study tested 825 healthy blood donors, and 130 came back positive on at least one antibody test. Then it followed them for five years. Only two ever got an autoimmune rheumatic diagnosis, which is two out of a hundred and thirty.
One study followed 263 patients sent to a rheumatologist purely because their ANA was positive. Of those, 24 percent got a diagnosis of a disease linked to that antibody, and 26 percent had no sign of any disease at all. Another 39 percent had a rheumatology diagnosis unrelated to their antibodies.
What the number means.
| Dilution | Positive in healthy people | What it means | Source |
|---|---|---|---|
| 1 to 40 | 31.7 percent | Almost a third of healthy people. So a positive result here tells you very little on its own. | Tan 1997 |
| 1 to 80 | 13.3 percent | The dilution most US labs report. About one healthy person in seven is positive. | Tan 1997 |
| 1 to 160 | 5.0 percent | Where the famous five percent figure comes from. It belongs to this dilution and no other. | Tan 1997 |
| 1 to 320 | 3.3 percent | Uncommon in healthy people, so more likely to count. It still isn''t a diagnosis. | Tan 1997 |
| Across the whole US | 13.8 percent | At a single 1 to 80 dilution, in everyone aged 12 and over. It was 17.8 percent of women against 9.6 percent of men. | Satoh 2012 |
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.
What the test measures
An antinuclear antibody test looks for antibodies aimed at parts of your own cell nuclei. The traditional method puts your watered-down blood onto cultured cells, usually a line called HEp-2, and somebody then looks under a microscope for a glowing pattern where antibodies have stuck. Newer bead tests look for a set list of specific antibodies instead, and the two methods don't always agree with each other.
The result comes in two parts, and the second is the one people usually don't get told about. The first is whether antibodies were found at all, and the second is how far your blood could be watered down while they still showed. That second number is the titer, so a titer of 1 to 320 means antibodies still showed after the blood was watered down 320 times.
That number holds most of the meaning, and a result quoted without it can barely be read. If your report gives a positive or negative with no titer beside it, that is a report missing its most useful half. So ask for the number, because you are entitled to it.
How common a positive result is
The definitive study here dates from 1997, and it's the reason the dilution counts for so much. Fifteen reference labs around the world tested blood from apparently healthy people on HEp-2 cells and reported how many were positive at each dilution. At 1 to 40, 31.7 percent were positive, at 1 to 80 it was 13.3 percent, at 1 to 160 it was 5.0 percent, and at 1 to 320 it was 3.3 percent.
Read that sequence again, because it settles a good many arguments. Nearly a third of well people are positive at the lowest dilution labs commonly report, and the numbers didn't really differ across ages from twenty to sixty. So the famous claim that about 5 percent of healthy people have a positive ANA is only true at one dilution, and at the low ones it's badly wrong.
One study then tested 4,754 Americans chosen to stand for the whole country, using a single dilution of 1 to 80, and found 13.8 percent positive. That scales up to more than 32 million people, and hardly any of them have lupus, which affects a small fraction of one percent of people. So the arithmetic alone tells you a positive result usually means nothing.
What happens when you screen well people
Two studies show what this test does when no clinical question is being asked, and they're worth knowing before you request a panel. One screened healthy volunteers and followed them for years, and the other tracked what happened after a positive result triggered a referral. Neither is reassuring about screening.
Swedish researchers screened 825 healthy blood donors using both methods, meaning the microscope one and the bead one, and 130 of them, 15.8 percent, were positive on at least one. Thirty-seven agreed to a clinical assessment, and two women got a diagnosis of Sjogren disease. Across five years of follow-up, only those two had received an autoimmune rheumatic diagnosis, and what people said about their symptoms matched the antibody results poorly.
The other study looked at what happens after a positive result triggers a referral, covering 15,357 patients sent through one rheumatology triage system. Of those, 643 were sent because their ANA was positive and 263 got seen by a rheumatologist, where 24 percent got a diagnosis of a disease linked to that antibody, with lupus and Sjogren disease each making up about 9 percent. Twenty-six percent had no sign of any disease at all, and 39 percent had a rheumatology diagnosis that had nothing to do with their antibodies.
Where the test is genuinely useful
This test's value lies almost entirely in a negative result, and that's a real clinical use rather than a consolation prize. The 2019 European and American classification rules for lupus use an ANA at 1 to 80 or above on HEp-2 cells as the door you have to come through. They picked it for that job because it catches 97.8 percent of lupus cases, with the true figure somewhere from 96.8 to 98.5 percent.
So a negative ANA at that dilution makes lupus very unlikely, which is worth a great deal when somebody turns up with symptoms that could point that way. The full rulebook caught 96.1 percent of cases and cleared 93.4 percent of healthy people when it was checked. The older 1997 rules caught 82.8 percent, and a 2012 set caught 96.7 percent while clearing only 83.7 percent.
The lopsidedness is the point of the whole page. A negative result rules out well. A positive result, on its own, rules almost nothing in at all.
Living with a positive result
A positive ANA with no symptoms is common and genuinely hard, because there's nothing to treat and something to worry about. The fair approach is an assessment that looks at what a doctor finds on examining you, your history, and more specific antibodies, followed by a decision about whether anything needs following. Many people in this spot need nothing beyond knowing what the result does and doesn't mean.
Suppose instead that you feel unwell and your ANA is positive. That combination deserves a proper look rather than dismissal in either direction. A quarter of people sent in for a positive ANA do have a linked disease, and another 39 percent had a different rheumatology diagnosis worth finding, so the antibody is a reason to look carefully and the looking is what produces the answer.
Repeating it
The ANA isn't used to follow how active your disease is, so repeating it once you know the result rarely changes anything. Titers wobble for reasons that have nothing to do with how your disease is behaving, so a rise doesn't mean you're getting worse and a fall doesn't mean you're getting better. That surprises people, and it's the most common reason a repeat test causes worry it shouldn't.
What does follow your disease is your examination, your symptoms, organ-specific testing, and more specific antibodies where they apply. Those are the things worth repeating. If somebody is reordering your ANA every few months, it's fair to ask what decision the result would change.
Common misconceptions.
Myth. A positive ANA means I have lupus.
Reality. Not on its own, and one study makes that concrete. It looked at 263 ANA-positive patients seen by a rheumatologist, where 24 percent got a diagnosis of a disease linked to that antibody and only 9.1 percent had lupus. A quarter had no sign of any disease at all.
Myth. A positive ANA in a healthy person is the start of something.
Reality. Usually not, and there's a study built around that question. It tested 825 blood donors, 130 of whom came back positive, and over five years of follow-up two of them got an autoimmune rheumatic diagnosis. So most positive results in people without symptoms just stay that way.
Myth. About five percent of healthy people have a positive ANA.
Reality. That figure is right at one dilution and nowhere else, and the dilution is 1 to 160. At 1 to 40 the figure is 31.7 percent, and at 1 to 80, which is what many labs report, it's 13.3 percent. So the number people quote is correct and almost never the one that applies to their own report.
Myth. A negative ANA rules lupus out.
Reality. It very nearly does, which is a different claim from ruling it out. The 2019 European and American rules use a positive ANA as the door you have to come through, and the figure behind that choice is high rather than perfect. It catches 97.8 percent of cases, which is not all of them.
Questions patients ask.
My ANA is positive. Do I have lupus?
Almost certainly not on that alone, because a positive ANA is common in people with no disease, and how common depends on the dilution. At 1 to 40, nearly a third of healthy people are positive, and at 1 to 320 it's about 3 percent. Look at the patients sent to a rheumatologist just for a positive ANA, where 24 percent turned out to have a linked disease and 26 percent had no sign of any.
Why does the titer matter so much?
Because one result at different dilutions means completely different things. The lab waters your blood down step by step, and the number records how far it got while antibodies still showed. At 1 to 40, nearly a third of healthy people are positive, so that finding is close to meaningless, while at 1 to 320 only about 3 percent are, so that one is worth explaining. A result quoted with no dilution can't be read at all.
Can I have lupus with a negative ANA?
It's very unusual, and that's what makes the test useful. The 2019 European and American classification rules use an ANA of 1 to 80 or above as the door you have to come through, and they picked it for that job because it catches 97.8 percent of lupus cases. So a negative result at that dilution makes lupus very unlikely. This test is much better at ruling out disease than at confirming it.
Should I have my ANA checked as a screen?
Not without a clinical reason, and the numbers show why. One study tested 825 healthy blood donors, found 130 positive on at least one test, and over five years produced two rheumatic diagnoses, while what people said about their symptoms matched the antibody results poorly. So nearly all the positives in a screened group are people who are perfectly well, and finding them does no good at all.
My ANA is positive and I feel unwell. What now?
A rheumatology assessment is fair, though go in expecting a proper look rather than a verdict from the number. The doctor will weigh what they find on examining you, your history, and more specific antibodies, which count for far more than the ANA does. The odds are worth knowing too, because a quarter of people sent in for a positive ANA do have a linked disease, and another 39 percent had a different rheumatology diagnosis worth finding.
Should I keep repeating the test?
Rarely, once you know the result, because the ANA doesn't track how active your disease is. A number going up or down doesn't mean you're getting worse or better, and it doesn't guide treatment either. Repeat testing tends to throw up wobbles that need explaining. What follows your disease is your examination, your symptoms, and the more specific tests that belong to your particular diagnosis.
References.
- Tan EM; Feltkamp TE; Smolen JS et al. Range of antinuclear antibodies in "healthy" individuals. Arthritis and rheumatism. 1997;40:1601-11. 10.1002/art.1780400909Multicentre cross-sectional study of a putatively normal population across 15 international laboratories
- Satoh M; Chan E; Ho L et al. Prevalence and sociodemographic correlates of antinuclear antibodies in the United States. Arthritis & Rheumatism. 2012;64:2319-2327. 10.1002/art.34380Cross-sectional analysis of a nationally representative population survey
- Andraos R; Ahmad A; Wirestam L et al. Screening for autoimmune diseases in apparently healthy antinuclear antibody positive individuals. Frontiers in Medicine. 2024;11. 10.3389/fmed.2024.1455673Prospective screening study of 825 consecutive apparently healthy blood donors with structured questionnaire
- Fitch-Rogalsky C; Steber W; Mahler M et al. Clinical and Serological Features of Patients Referred through a Rheumatology Triage System because of Positive Antinuclear Antibodies. PLoS ONE. 2014;9:e93812. 10.1371/journal.pone.0093812Cross-sectional retrospective analysis of a central rheumatology triage database
- Aringer M; Costenbader K; Daikh D et al. 2019 European League Against Rheumatism/American College of Rheumatology Classification Criteria for Systemic Lupus Erythematosus. Arthritis & Rheumatology. 2019;71:1400-1412. 10.1002/art.40930Multiphase classification criteria development with derivation
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.