From the Guidelines
Several medications can interfere with antinuclear antibody (ANA) blood test results, including hydralazine, procainamide, isoniazid, minocycline, and certain anticonvulsants like phenytoin and carbamazepine, which can cause drug-induced lupus or create false positive results. These medications can trigger autoantibody production that mimics autoimmune conditions, leading to positive ANA results that may not reflect true autoimmune disease 1.
Medications Affecting ANA Test Results
Some of the key medications that can affect ANA test results include:
- Hydralazine
- Procainamide
- Isoniazid
- Minocycline
- Phenytoin
- Carbamazepine
- TNF inhibitors (infliximab, etanercept, adalimumab)
- Methyldopa
- Chlorpromazine
- Quinidine
- Sulfasalazine
- Certain antibiotics (penicillin, cephalosporins)
- Antihistamines
- Over-the-counter medications like ibuprofen and naproxen
Clinical Implications
It is essential to inform healthcare providers about all medications being taken, including prescription drugs, over-the-counter medications, and supplements, before undergoing an ANA test 1. In some cases, healthcare providers may recommend temporarily discontinuing certain medications before testing, although patients should never stop prescribed medications without medical guidance. The false positive results typically resolve within weeks to months after discontinuing the triggering medication.
Laboratory Considerations
Laboratories should specify the methods used for detecting ANA when reporting their results, and tests based on a restricted mixture of defined nuclear antigens should not be referred to as ANA tests or ANA screens 1. The indirect immunofluorescent assay (IIFA) is the reference method for ANA screening, and alternative assays can be used while keeping in mind that false negative and false positive ratios of these methods may be different.
From the FDA Drug Label
Laboratory tests such as complete blood count (CBC), electrocardiogram and serum creatinine or urea nitrogen may be indicated depending on the clinical situation, and periodic rechecking of the CBC and ANA may be helpful in early detection of untoward reactions Drug/Laboratory Test Interactions Suprapharmacologic concentrations of lidocaine and meprobamate may inhibit fluorescence of PA and NAPA, and propranolol shows a native fluorescence close to the PA/NAPA peak wavelengths, so that tests which depend on fluorescence measurement may be affected.
The following drugs can affect the Antinuclear Antibody (ANA) blood test:
- Procainamide (PA): may cause untoward reactions that can be detected by periodic rechecking of the ANA
- Lidocaine and meprobamate: may inhibit fluorescence of PA and NAPA, potentially affecting tests that depend on fluorescence measurement, including the ANA test
- Propranolol: may interfere with tests that depend on fluorescence measurement due to its native fluorescence close to the PA/NAPA peak wavelengths 2
From the Research
Drugs Affecting the Antinuclear Antibody (ANA) Blood Test
The following drugs have been reported to affect the ANA blood test:
- Hydralazine: This drug has been shown to induce systemic lupus erythematosus (SLE) and stimulate the production of antinuclear antibodies (ANA) 3, 4, 5, 6.
- Procainamide: Similar to hydralazine, procainamide has been associated with the development of SLE and the production of ANA 3.
- Isoniazid: This drug has been reported to induce SLE and elevate ANA levels 7.
- Methyldopa: Although not directly mentioned in the provided studies, methyldopa has been listed as a drug that can induce SLE 5, 7.
- Chlorpromazine: This drug has been associated with the development of SLE 5, 7.
- Quinidine: Quinidine has been listed as a drug that can induce SLE 5, 7.
- Minocycline: This drug has been associated with the development of SLE 5, 7.
- Estrogen-containing oral contraceptives: These have been shown to exacerbate idiopathic SLE 3.
- Ibuprofen: This drug has been reported to exacerbate idiopathic SLE 3.
Clinical Implications
It is essential to consider the potential effects of these drugs on the ANA blood test, as false positives or false negatives can lead to misdiagnosis or delayed diagnosis of SLE. Baseline ANA status should be determined before therapy with these drugs, and patients should be observed carefully for signs and symptoms of SLE 3.