{"id":"rheumatoid-factor","name":"Rheumatoid Factor (RF)","shortName":"RF","aliases":["Rheumatoid Factor","RF","RF, Quantitative","RA Latex","RA Factor","Rheumatoid Arthritis Factor","Factor reumatoide","Rheumatoid Factor, Serum","Rheumatoid Factor, Quantitative","Rheumatoid Factor (RF), Quantitative","RF Quant","RA Factor, Quantitative","Rheumatoid Arthritis (RA) Factor","Rheumatoid Factor Latex","RF Latex","RA Latex Turbidimetric"],"abbreviations":["RF","RA Factor"],"loinc":[{"code":"11572-5","primary":true},{"code":"6928-6","primary":false},{"code":"15205-8","primary":false},{"code":"33910-1","primary":false},{"code":"5297-7","primary":false},{"code":"17857-4","primary":false},{"code":"5299-3","primary":false}],"specimen":"serum-or-plasma","units":[{"ucum":"[IU]/mL","display":"IU/mL"},{"ucum":"k[IU]/L","display":"kIU/L"}],"referenceRanges":[{"population":"Adults","low":0,"high":14,"unit":"[IU]/mL","unitDisplay":"IU/mL","note":"Typical US total-RF cutoff. Quest reports a range of below 14 IU/mL, Labcorp below 14.0 IU/mL (latex immunoturbidimetry), ARUP 0 to 14 IU/mL (immunoturbidimetry) and Mayo Clinic Laboratories below 15 IU/mL (turbidimetry). Cutoffs are set by the test maker and are not the central 95% of healthy people, since many healthy people have some RF. IgM-only assays can use a much lower cutoff (Mayo's RF IgM chemiluminescent assay is negative below 5.0 IU/mL), so use the cutoff and flag printed on your own report.","sources":[{"title":"Rheumatoid Factor (test 0050465)","url":"https://ltd.aruplab.com/Tests/Pub/0050465","publisher":"ARUP Laboratories"},{"title":"Rheumatoid Factor (test 4418)","url":"https://testdirectory.questdiagnostics.com/test/test-detail/4418/rheumatoid-factor?cc=MASTER","publisher":"Quest Diagnostics"},{"title":"Rheumatoid Factor (RF) (test 006502)","url":"https://www.labcorp.com/tests/006502/rheumatoid-factor-rf","publisher":"Labcorp"}]}],"review":{"status":"ai-verified","label":"AI-verified against cited sources. Awaiting expert review","lastReviewed":"2026-10-03"},"summary":"A blood test for rheumatoid factor, an antibody often found in rheumatoid arthritis but also in other conditions and in some healthy people.","url":"https://bloodtesttracker.com/markers/rheumatoid-factor","notice":"Information, not medical advice. Ranges differ between labs, so the range on your own report is the one your result is judged against."}