Diagnosis of systemic lupus erithematosus (SLE) is considered possible if at least 4 of these 11 criteria for SLE are present (according to the American Rheumatologic Association):
1. Malar rash (facial rash that looks like a butterfly);
2. Discoid lupus (disc-like rush with hyperkeratosis and atrophy on the skin);
3. Photosensitivity;
4. Painless ulcerations of the oral and nasal mucosa;
5. Arthritis on 2 or more peripheral joints;
6. Pleurisy or pericarditis;
7. Signs for renal failure (proteins in the urine, erythrocytes and cellular casts in the urinary sediment);
8. Neurological manifestations (psychoses and /or convulsions);
9. Hematological disturbances (anemia, leukopenia, lymphopenia, thrombocytopenia);
10. Immunological reports (anti-DNA-antibodies, anti-Sm-antibodies, positive lupus band test of the skin, LE-cells, false positive result for syphilis(anti-cardiolipin-antibodies) ), and
11. High titer of anti nuclear antibodies (ANA)
The medicine Claritin doesn’t affect the serology blood results for SLE. Anti-DNA-antibodies are very specific for SLE but it is possible that the antibodies haven't been created yet. You can consult a rheumatologist and request some of the additional tests mentioned above to confirm or exclude SLE.