|Values are valid only on day of printing.|
Histones are the most basic protein components of chromatin and their structures are highly conserved in different species. Five classes of histones called H1, H2, H2b, H3, and H4 have been described and are characterized by their molecular weights, ranging from 11 to 23 kilodalton (kD), and their content of the basic amino acids lysine and arginine.
Histone autoantibodies may react with any of the 5 classes of histones.(1,2) Autoantibodies to total histones are elicited by unknown mechanisms in patients treated with certain drugs, particularly procainamide, hydralazine, quinidine, alpha methyldopa, penicillamine, and isoniazid. Those patients may have signs and symptoms that resemble systemic lupus erythematosus (SLE). This disorder is identified as drug-induced lupus. Testing for autoantibodies to total histones is useful for evaluating patients suspected of having drug-induced lupus. Such patients will usually have a positive test for histone autoantibodies and a negative test for autoantibodies to double stranded DNA (dsDNA). Patients with SLE have positive tests for both types of autoantibodies.
Evaluating patients suspected of having drug-induced lupus
A positive result for histone autoantibodies with a negative result for autoantibodies to double-stranded DNA (anti-ds-DNA) is consistent with drug-induced lupus.
A positive result for histone autoantibodies with a positive result for anti-dsDNA autoantibodies is consistent with systemic lupus erythematosus.
Positive tests for histone autoantibodies occur in some patients exposed to the above mentioned drugs who do not have signs or symptoms of lupus.
Testing for histone autoantibodies is not necessary to establish the diagnosis of systemic lupus erythematosus (SLE).
Test results are not useful for determining prognosis in patients with SLE or drug-induced lupus.
<1.0 Units (negative)
1.0-1.5 Units (borderline)
>1.5 Units (positive)
Units are arbitrarily based on positive control serum.
Reference values apply to all ages.
1. Borchers AT, Keen CL, Gershwin ME: Drug-induced lupus. Ann NY Acad Sci 2007;1108:166-182
2. S Vasoo. Drug-induced lupus: An update. Lupus 2006;15:757-761