Rheumatoid factor test cost in New York, NY
In New York-Newark-Jersey City, NY-NJ, 82 hospitals list a cash price for rheumatoid factor (RF) test: from $5.00 to $273.24, with a median of $6.52. The lowest listed price is at Saint Marys Hospital — $1.52 less than the median here. Across New York, the median is $20.93 at 112 hospitals.
- The median here, $6.52, is 84% below the US median of $40.48.
- That is 1.1× Medicare's 2026 national rate for the same service ($5.67).
- New York, NY has the lowest median of 2 metro areas in New York with at least 10 hospitals pricing this code.
- 16 of 82 hospitals list a cash price equal to their full list price, with no self-pay discount.
Cash prices at 82 facilities across 58 cities for code 86431, as an outpatient — the setting a self-pay patient normally buys. Collected Nov 11, 2026; the hospital files themselves were last updated between Oct 28, 2025 and Sep 28, 2026.
Lowest$5.00Saint Marys Hospital
Median$6.52half of hospitals charge less
Highest$273.24in this market
Difference54.6×highest vs lowest
Where each hospital's price falls
Each dot is one hospital's cash price on a scale from the lowest to the highest in New York-Newark-Jersey City, NY-NJ.
median
Lowest $5.00Highest $350.10
Hospitals, cheapest first
| Hospital | Cash price | List price | Insurers pay | Off list |
|---|---|---|---|---|
| Saint Marys Hospital lowest Passaic, NJ · (973) 365-4300 Hc Rheumatoid Factor, Quant File of Sep 1, 2026 · source file | $5.00 | $50.00 | $3.40–$42.50 | 90% |
| Interfaith Medical Center Brooklyn, NY RHEUMATOID FACTOR TITER File of Aug 1, 2026 · source file | $5.25 | $14.00 | $4.93–$11.82 | 63% |
| Brookdale Hospital Medical Center Brooklyn, NY · (718) 240-5966 RHEUMATOID FACTOR TITER File of Aug 1, 2026 · source file | $5.25 | $14.00 | $4.93–$11.82 | 63% |
| Kingsbrook Jewish Medical Center Brooklyn, NY RHEUMATOID FACTOR TITER File of Aug 1, 2026 · source file | $5.25 | $14.00 | $4.93–$11.82 | 63% |
| Palisades Medical Center North Bergen, NJ · (201) 854-5000 RHEUMATOID FACTOR BODY FLUID ARUP+9 more lines at this price File of Dec 31, 2025 · source file | $5.67 | $21.00 | $5.67–$25.98 | 73% |
| Southern Ocean Medical Center Manahawkin, NJ · (609) 597-6011 RHEUMATOID FACTOR- QUANT FLUI+9 more lines at this price File of Dec 31, 2025 · source file | $5.67 | $114.00 | $3.89–$116.06 | 95% |
| Old Bridge Medical Center Old Bridge, NJ RHEUMATOID FACTOR- QUANT FLUI+9 more lines at this price File of Dec 31, 2025 · source file | $5.67 | $114.00 | $2.79–$202.36 | 95% |
| Raritan Bay Medical Center Perth Amboy, NJ · (732) 324-5000 RHEUMATOID FACTOR- QUANT FLUI+9 more lines at this price File of Dec 31, 2025 · source file | $5.67 | $114.00 | $2.79–$202.36 | 95% |
| Ocean Medical Center Brick, NJ · (732) 840-2200 RHEUMATOID FACTOR- QUANT FLUI+19 more lines at this price File of Dec 31, 2025 · source file | $5.67 | $114.00 | $2.98–$202.43 | 95% |
| South Brooklyn Health Brooklyn, NY · (718) 616-4834 HC RHEUMATOID FACTOR; QUANTITATIVE File of Sep 5, 2026 · source file | $5.67 | $23.78 | $1.00–$21.77 | 76% |
| Bellevue Hospital Center New York, NY · (212) 561-4132 HC RHEUMATOID FACTOR; QUANTITATIVE File of Sep 5, 2026 · source file | $5.67 | $23.78 | $5.56–$108.88 | 76% |
| St Joseph's Hospital, Yonkers Yonkers, NY · (914) 378-7000 Rheumatoid factor quant+3 more lines at this price File of Jul 13, 2026 · source file | $5.67 | — | $4.93–$291.42 | — |
| Jacobi Medical Center Bronx, NY · (718) 918-5000 HC RHEUMATOID FACTOR; QUANTITATIVE File of Sep 5, 2026 · source file | $5.67 | $23.78 | $5.56–$123.84 | 76% |
| Hackensack University Medical Center Hackensack, NJ · (551) 996-2000 RHEUMATOID FACTOR- QUANT FLUI+9 more lines at this price File of Dec 31, 2025 · source file | $5.67 | $114.00 | $5.27–$208.00 | 95% |
| Kings County Hospital Center Brooklyn, NY · (718) 245-3901 HC RHEUMATOID FACTOR; QUANTITATIVE File of Sep 5, 2026 · source file | $5.67 | $23.78 | $1.00–$21.77 | 76% |
| Elmhurst Hospital Center Broadway Elmhurst, NY · (718) 334-1141 HC RHEUMATOID FACTOR; QUANTITATIVE File of Sep 5, 2026 · source file | $5.67 | $23.78 | $1.00–$21.63 | 76% |
| North Central Bronx Hospital Bronx, NY HC RHEUMATOID FACTOR; QUANTITATIVE File of Sep 5, 2026 · source file | $5.67 | $23.78 | $1.00–$21.56 | 76% |
| Queens Hospital Center Jamaica, NY · (718) 883-3000 HC RHEUMATOID FACTOR; QUANTITATIVE File of Sep 5, 2026 · source file | $5.67 | $23.78 | $5.56–$99.63 | 76% |
| Lincoln Medical & Mental Health Center Bronx, NY · (718) 579-5000 HC RHEUMATOID FACTOR; QUANTITATIVE File of Sep 5, 2026 · source file | $5.67 | $23.78 | $1.00–$21.84 | 76% |
| Riverview Medical Center Red Bank, NJ · (732) 741-2700 RHEUMATOID FACTOR- QUANT FLUI+9 more lines at this price File of Dec 31, 2025 · source file | $5.67 | $114.00 | $2.96–$203.74 | 95% |
| Metropolitan Hospital Center New York, NY · (212) 423-6262 HC RHEUMATOID FACTOR; QUANTITATIVE File of Sep 5, 2026 · source file | $5.67 | $23.78 | $1.00–$21.77 | 76% |
| Harlem Hospital Center New York, NY · (212) 939-1000 HC RHEUMATOID FACTOR; QUANTITATIVE File of Sep 5, 2026 · source file | $5.67 | $23.78 | $5.56–$99.86 | 76% |
| Woodhull Medical & Mental Health Center Brooklyn, NY · (718) 963-8100 HC RHEUMATOID FACTOR; QUANTITATIVE File of Sep 5, 2026 · source file | $5.67 | $23.78 | $1.00–$21.77 | 76% |
| Bayshore Medical Center Holmdel, NJ · (732) 739-5900 RHEUMATOID FACTOR- QUANT FLUI+9 more lines at this price File of Dec 31, 2025 · source file | $5.67 | $114.00 | $5.67–$148.90 | 95% |
| Jersey Shore University Medical Center Neptune City, NJ · (732) 775-5500 RHEUMATOID FACTOR- QUANT FLUI+9 more lines at this price File of Dec 31, 2025 · source file | $5.67 | $114.00 | $3.49–$208.00 | 95% |
| JFK University Medical Center Edison, NJ · (732) 321-7000 RHEUMATOID FACTOR- QUANT FLUI+19 more lines at this price File of Dec 31, 2025 · source file | $5.67 | $114.00 | $3.38–$196.77 | 95% |
| Cooperman Barnabas Medical Center Livingston, NJ · (973) 322-5000 HC Rheumatoid Factor Quantitative File of Mar 4, 2026 · source file | $6.24 | $131.00 | $2.66–$111.35 | 95% |
| Newark Beth Israel Medical Center Newark, NJ · (973) 926-7000 HC Rheumatoid Factor Quantitative File of Mar 4, 2026 · source file | $6.24 | $131.00 | $2.66–$122.26 | 95% |
| Robert Wood Johnson University Hospital Rahway Rahway, NJ · (732) 381-4200 HC Rheumatoid Factor Quantitative File of Mar 4, 2026 · source file | $6.24 | $130.00 | $2.66–$87.36 | 95% |
| Robert Wood Johnson University Hospital New Brunswick New Brunswick, NJ · (732) 828-3000 HC Rheumatoid Factor Quantitative File of Mar 4, 2026 · source file | $6.24 | $131.00 | $2.66–$108.99 | 95% |
| Robert Wood Johnson University Hospital Somerset Somerville, NJ · (908) 685-2200 HC Rheumatoid Factor Quantitative File of Mar 4, 2026 · source file | $6.24 | $130.00 | $2.66–$118.92 | 95% |
| Trinitas Regional Medical Center Elizabeth, NJ · (908) 994-5000 HC Rheumatoid Factor Quantitative File of Mar 4, 2026 · source file | $6.24 | $104.00 | $2.66–$66.32 | 94% |
| Monmouth Medical Center Long Branch, NJ · (732) 222-5200 HC Rheumatoid Factor Quantitative File of Mar 4, 2026 · source file | $6.24 | $104.00 | $2.66–$100.57 | 94% |
| Monmouth Medical Center Southern Campus Lakewood, NJ · (732) 363-1900 HC Rheumatoid Factor Quantitative File of Mar 3, 2026 · source file | $6.24 | $104.00 | $2.66–$100.99 | 94% |
| Community Medical Center Toms River, NJ · (732) 557-8000 HC Rheumatoid Factor Quantitative File of Mar 4, 2026 · source file | $6.24 | $104.00 | $2.66–$95.14 | 94% |
| Jersey City Medical Center Jersey City, NJ · (201) 915-2000 HC Rheumatoid Factor Quantitative File of Mar 4, 2026 · source file | $6.24 | $104.00 | $2.66–$94.40 | 94% |
| Clara Maass Medical Center Belleville, NJ · (973) 450-2000 HC Rheumatoid Factor Quantitative File of Mar 4, 2026 · source file | $6.24 | $81.00 | $2.66–$77.32 | 92% |
| Newton Medical Center Newton, NJ · (973) 383-2121 Rheumatoid Factor Quant File of Apr 1, 2026 · source file | $6.52 | $61.00 | — | 89% |
| Chilton Medical Center Pompton Plains, NJ · (973) 831-5000 Rheumatoid Factor Quant File of Apr 1, 2026 · source file | $6.52 | $61.00 | — | 89% |
| Morristown Medical Center Morristown, NJ · (973) 971-5450 Rheumatoid Factor Quant File of Apr 1, 2026 · source file | $6.52 | $61.00 | — | 89% |
| University Hospital Newark, NJ · (973) 972-4300 RHEUMATOID FACTOR QUANTITATIVE File of Aug 13, 2026 · source file | $6.52 | $188.31 | $4.49–$178.89 | 97% |
| CentraState Medical Center Freehold Township, NJ · (732) 294-7012 Rheumatoid Factor Quant File of Apr 1, 2026 · source file | $6.52 | $61.00 | — | 89% |
| Overlook Medical Center Summit, NJ · (908) 522-2000 Rheumatoid Factor Quant File of Apr 1, 2026 · source file | $6.52 | $61.00 | — | 89% |
| Hackensack Meridian Mountainside Medical Center Montclair, NJ · (973) 429-6000 Rheumatoid factor level File of Feb 12, 2026 · source file | $6.52 | $68.25 | $5.67–$68.25 | 90% |
| NYU Langone Brooklyn, NY HC RHEUMATOID FACTOR, QUANT File of Jan 1, 2026 · source file | $6.80 | $71.00 | $5.10–$169.02 | 90% |
| NYU Langone – Orthopedic Hospital New York, NY HC RHEUMATOID FACTOR, QUANT File of Jan 1, 2026 · source file | $6.80 | $71.00 | $5.10–$169.02 | 90% |
| NYU Langone Mineola, NY HC RHEUMATOID FACTOR, QUANT File of Jan 1, 2026 · source file | $6.80 | $71.00 | $5.10–$169.02 | 90% |
| NYU Langone – Tisch Hospital New York, NY · (212) 263-7300 HC RHEUMATOID FACTOR, QUANT File of Jan 1, 2026 · source file | $6.80 | $71.00 | $5.10–$169.02 | 90% |
| NYU Langone Hospital - Suffolk Patchogue, NY · (631) 654-7100 HC RHEUMATOID FACTOR, QUANT File of Jan 1, 2026 · source file | $6.80 | $71.00 | $5.10–$169.02 | 90% |
| Bronx-Lebanon Hospital Center - Concourse Division Bronx, NY · (212) 588-7000 RHEUMATOID FACTOR QUANT File of Apr 17, 2026 · source file | $12.47 | $12.47 | — | — |
| BronxCare Hospital Center - Fulton Campus Bronx, NY · (212) 588-7000 RHEUMATOID FACTOR QUANT File of May 5, 2026 · source file | $12.47 | $12.47 | — | — |
| Nassau University Medical Center East Meadow, NY · (516) 572-0123 Rheumatoid Factor File of Oct 28, 2025 · source file | $13.30 | $19.00 | $2.32–$625.00 | 30% |
| Montefiore Mount Vernon Hospital Mount Vernon, NY · (914) 664-8000 HC RHEUMATOID FACTOR QUANT File of Sep 28, 2026 · source file | $13.65 | $21.00 | $3.94–$61.49 | 35% |
| Englewood Health Englewood, NJ · (201) 894-3000 Ra Titer 86431 File of Feb 2, 2026 · source file | $14.90 | $149.00 | $11.65–$119.20 | 90% |
| Nassau University Medical Center East Meadow, NY · (516) 572-0123 Rheum Factor Nephlo File of Oct 28, 2025 · source file | $14.96 | $21.37 | $2.32–$625.00 | 30% |
| Jamaica Hospital Medical Center Jamaica, NY · (718) 262-6000 RHEUMATOID FACTOR LEVEL File of Mar 25, 2026 · source file | $17.00 | $17.00 | $4.82–$1,912.00 | — |
| Flushing Hospital Medical Center Flushing, NY · (718) 670-5000 RHEUMATOID FACTOR LEVEL File of Mar 25, 2026 · source file | $17.00 | $17.00 | $4.82–$1,912.00 | — |
| St. Catherine of Siena Medical Center Smithtown, NY · (631) 862-3000 HC RHEUMATOID FACTOR TITER Q#10716 (PX 1)+2 more lines at this price File of Feb 19, 2026 · source file | $20.93 | $25.00 | $0.01–$161.00 | 16% |
| Mercy Medical Center Rockville Centre, NY · (516) 705-2525 HC FLUID RHEUMATOID FACTOR+2 more lines at this price File of Feb 19, 2026 · source file | $20.93 | $161.00 | $5.25–$161.00 | 87% |
| St. Francis Hospital Roslyn, NY HC FLUID RHEUMATOID FACTOR+2 more lines at this price File of Feb 19, 2026 · source file | $20.93 | $161.00 | $5.25–$161.00 | 87% |
| Good Samaritan Hospital Medical Center West Islip, NY · (631) 376-3000 HC FLUID RHEUMATOID FACTOR+2 more lines at this price File of Feb 19, 2026 · source file | $20.93 | $161.00 | $5.25–$161.00 | 87% |
| Chsli St Joseph Hospital Bethpage, NY · (516) 759-6000 HC FLUID RHEUMATOID FACTOR+2 more lines at this price File of Feb 19, 2026 · source file | $20.93 | $161.00 | $5.25–$161.00 | 87% |
| Englewood Health Englewood, NJ · (201) 894-3000 Xpld-Identra Ra Pan(Rafq)86431 File of Feb 2, 2026 · source file | $24.40 | $244.00 | $19.08–$195.20 | 90% |
| Flushing Hospital Medical Center Flushing, NY · (718) 670-5000 RHEUMATOID FACTOR QUANT File of Mar 25, 2026 · source file | $27.00 | $27.00 | $4.82–$1,912.00 | — |
| Englewood Health Englewood, NJ · (201) 894-3000 Rheumatoid Factor 86431 File of Feb 2, 2026 · source file | $27.20 | $272.00 | $21.27–$217.60 | 90% |
| Maimonides Medical Center Brooklyn, NY · (718) 283-6000 RHEUMATOID QUAN File of Apr 1, 2026 · source file | $29.00 | $29.00 | — | — |
| The Valley Hospital Paramus, NJ · (201) 447-8000 RHEUMATOID FACTOR (RF) File of May 6, 2026 · source file | $30.60 | $51.00 | $4.54–$43.35 | 40% |
| St Johns Episcopal Hospital Far Rockaway, NY · (718) 869-7000 RHEUMATOID FACTOR QUANT File of Apr 7, 2026 · source file | $34.06 | $40.07 | $5.39–$12.88 | 15% |
| Hudson Regional Hospital Secaucus, NJ · (201) 392-3200 Rheumatoid factor level File of Sep 23, 2026 · source file | $39.00 | $39.00 | $5.67–$73.59 | — |
| Englewood Health Englewood, NJ · (201) 894-3000 Xpld- áRheumatoid Factor Quantitative Elisa, Iga+1 more line at this price File of Feb 2, 2026 · source file | $44.80 | $448.00 | $35.03–$358.40 | 90% |
| Jamaica Hospital Medical Center Jamaica, NY · (718) 262-6000 RHEUMATOID FACTOR QUANT File of Mar 25, 2026 · source file | $48.00 | $48.00 | $4.82–$1,912.00 | — |
| Children's Specialized Hospital Mountainside, NJ · (732) 258-7050 HC Rheumatoid Factor Quantitative File of Mar 4, 2026 · source file | $49.50 | $99.00 | $4.54–$97.02 | 50% |
| Englewood Health Englewood, NJ · (201) 894-3000 Xpld-Rad Rheumatoid Factor (Turb) 86431 File of Feb 2, 2026 · source file | $51.60 | $516.00 | $40.35–$412.80 | 90% |
| Westchester Medical Center Valhalla, NY · (914) 493-7000 RHEUMATOID FACTOR QUANT File of Jul 28, 2026 · source file | $69.00 | $69.00 | $3.97–$69.00 | — |
| The Valley Hospital Paramus, NJ · (201) 447-8000 Rheumatoid Factor, BF (Mayo) File of May 6, 2026 · source file | $76.20 | $127.00 | $4.54–$107.95 | 40% |
| St Johns Riverside Hospital Park Care Pavillion Yonkers, NY · (914) 964-4444 RHEUMATOID FACTOR QUANT File of Mar 27, 2026 · source file | $83.30 | $98.00 | $5.39–$3,783.00 | 15% |
| Good Samaritan Hospital Suffern, NY · (914) 368-5000 Rheumatoid Arthritis Profile LC+1 more line at this price File of Jun 29, 2026 · source file | $91.00 | $91.00 | $5.67–$267.50 | — |
| CentraState Medical Center Freehold Township, NJ · (732) 294-7012 Rheumatoid Factor Quant File of Apr 1, 2026 · source file | $102.94 | $1,807.00 | — | 94% |
| Stony Brook Southampton Hospital Southampton, NY RHEUMATOID FACTOR LEVEL File of Jun 17, 2026 · source file | $105.19 | $105.19 | $5.67–$7.37 | — |
| The Valley Hospital Paramus, NJ · (201) 447-8000 RF IGA, by EIA File of May 6, 2026 · source file | $105.60 | $176.00 | $4.54–$149.60 | 40% |
| Stony Brook Southampton Hospital Southampton, NY RHEUMATOID FACTOR QUANT File of Jun 17, 2026 · source file | $116.89 | $116.89 | $5.67–$7.37 | — |
| Mount Sinai Brooklyn Brooklyn, NY · (212) 420-2000 HC Rheumatoid Factor Quant File of Apr 1, 2026 · source file | $126.00 | $140.00 | — | 10% |
| Mount Sinai Queens Long Island, NY HC Rheumatoid Factor Quant File of Apr 1, 2026 · source file | $126.00 | $140.00 | — | 10% |
| The Mount Sinai Hospital New York, NY · (212) 241-7981 HC Rheumatoid Factor Quant File of Apr 1, 2026 · source file | $126.00 | $140.00 | — | 10% |
| Mount Sinai Morningside New York, NY HC Rheumatoid Factor Quant File of Apr 1, 2026 · source file | $126.00 | $140.00 | — | 10% |
| Stony Brook University Hospital Stony Brook, NY · (631) 444-4000 RHEUMATOID FACTOR LEVEL File of Jun 10, 2026 · source file | $127.00 | $127.00 | $5.67–$4,255.00 | — |
| Brooklyn Hospital Center at Downtown Campus Brooklyn, NY · (718) 250-8000 RHEUMATOID FACTOR LEVEL File of Jul 27, 2026 · source file | $132.28 | $132.28 | $4.54–$11.34 | — |
| Stony Brook University Hospital Stony Brook, NY · (631) 444-4000 RHEUMATOID FACTOR QUANT File of Jun 10, 2026 · source file | $136.00 | $136.00 | $5.67–$4,255.00 | — |
| New York Community Hospital of Brooklyn Brooklyn, NY · (718) 692-5302 RHEUM FACTOR QUANT File of Apr 1, 2026 · source file | $136.34 | $136.34 | — | — |
| Memorial Hospital for Cancer and Allied Diseases West Harrison, NY HC Rhut - Rheumatoid Fctr, Srm File of Dec 1, 2025 · source file | $145.00 | $145.00 | $14.20–$130.50 | — |
| Memorial Hospital for Cancer and Allied Diseases Middletown, NJ HC Rhut - Rheumatoid Fctr, Srm File of Dec 1, 2025 · source file | $145.00 | $145.00 | $22.68–$130.50 | — |
| Memorial Hospital for Cancer and Allied Diseases Basking Ridge, NJ HC Rhut - Rheumatoid Fctr, Srm File of Dec 1, 2025 · source file | $145.00 | $145.00 | $22.68–$130.50 | — |
| Memorial Hospital for Cancer and Allied Diseases New York, NY HC Rhut - Rheumatoid Fctr, Srm File of Dec 1, 2025 · source file | $145.00 | $145.00 | $14.20–$130.50 | — |
| Brooklyn Hospital Center at Downtown Campus Brooklyn, NY · (718) 250-8000 RHEUMATOID FACTOR QUANT File of Jul 27, 2026 · source file | $151.45 | $151.45 | $4.54–$11.34 | — |
| Chilton Medical Center Pompton Plains, NJ · (973) 831-5000 Rheumatoid Factor Quant File of Apr 1, 2026 · source file | $226.08 | $2,235.00 | — | 90% |
| Newton Medical Center Newton, NJ · (973) 383-2121 Rheumatoid Factor Quant File of Apr 1, 2026 · source file | $273.07 | $5,740.00 | — | 95% |
| New York Eye and Ear Infirmary of Mount Sinai New York, NY · (212) 979-4000 RHEUMATOID FACTOR QUANT File of Apr 1, 2026 · source file | $273.24 | $303.60 | — | 10% |
| Overlook Medical Center Summit, NJ · (908) 522-2000 Rheumatoid Factor Quant File of Apr 1, 2026 · source file | $304.72 | $3,387.00 | — | 91% |
| Morristown Medical Center Morristown, NJ · (973) 971-5450 Rheumatoid Factor Quant File of Apr 1, 2026 · source file | $350.10 | $2,973.00 | — | 88% |
Hospital The hospital that published the price, its city and the line exactly as written in its price file.
Cash price The hospital's own price for a patient paying without insurance (“discounted cash” in its price file). Hospitals must publish it under federal law, 45 CFR 180.50. Call to confirm it before booking. More
List price The hospital's full chargemaster price (“gross charge”) before any discount. Almost nobody pays it; the gap to the cash price shows what the self-pay discount is worth. More
Insurers pay The lowest and highest rates this hospital has agreed with insurance plans for the same item, from its price file. If the cash price is below what your plan pays and you have not met your deductible, paying cash can cost you less. More
Off list How much lower the cash price is than the list price.
No cash discount This line's cash price equals the hospital's full list price. Many hospitals still reduce bills for uninsured patients: ask the billing office for its self-pay discount in writing. More
Outpatient: lowest $5.00, median $6.52, highest $273.24 — a 54.6× difference within the same market.
As an inpatient, the same code is billed by 31 facilities here, median $6.80. Inpatient and outpatient prices are not comparable and are kept on separate pages: the inpatient charge covers admission, not the same purchase.
Cash or insurance?
At 60 of 68 hospitals that publish insurer rates for this code here, the cash price is below the highest rate a health plan has negotiated, and at 9 it is below every plan's rate. If you have insurance but have not met your deductible, you usually pay your plan's negotiated rate, which falls somewhere in the "Insurers pay" column. Paying cash can cost less, but a cash payment usually does not count toward your deductible. Ask the hospital for both numbers before you book.
What rheumatoid factor test is, what the price covers and why prices differ: Rheumatoid factor test explained.