Measurement of antinuclear antibodies (ANAs) in serum is the most commonly performed screening test for autoantibodies in patients suspected of having SRD. SRDs are also called connective tissue diseases or collagen diseases. Examples of SRDs include SLE, mixed connective tissue disease (MCTD), Sjögren syndrome, scleroderma, CREST (calcinosis, Raynaud phenomenon, esophageal dysfunction, sclerodactyly, and telangiectasia) syndrome, RA, and polymyositis dermatomyositis.
The diagnosis of SLE is difficult because clinical signs and symptoms are varied and mimic other SRDs. SLE is characterized by the production of autoantibodies to nuclear antigens, that is, anti–double-stranded DNA (anti-dsDNA). SLE is a multisystem disease that can affect every organ system in the body, especially the kidneys.
Results of tests for ANAs by ELISA show that ELISA and traditional indirect IFA methods for ANA are substantially equivalent; however, ELISAs require less time and technical expertise, whereas IFAs are more sensitive. Many laboratories are using a combination of both methods. ANA samples are screened using an ELISA assay. All samples that screen positive or equivocal are titered using Hep-2 cells, and the titer and pattern are reported. In general, a titer ≥1:160 is considered significantly positive. Low-titer ANAs are common with advancing age. When cell culture substrates (Hep-2 cells) are used, the ANA incidence is 99% in SLE.
ANA screen: negative by ELISA and IFA methods
If positive by IFA, the specimen is titered and a pattern is reported.
ANA titer: <1:160
Collect a 7-mL blood serum sample in a red-topped tube. Observe standard precautions.
Label the specimen with the patient’s name, date, and tests ordered and place in a biohazard bag for transport to the laboratory.
A positive result does not confirm a disease; low titers of ANAs are present in older people and some apparently healthy, normal people.
The diagnosis of an SRD is based primarily on the presence of compatible clinical signs and symptoms. The results of tests for autoantibodies, including ANAs and specific autoantibodies (e.g., ribonucleoprotein [RNP], Smith [Sm], SSA, SSB, Scl-70, Jo-1), are ancillary. Additional diagnostic criteria include consistent histopathology or specific radiographic findings.
Pretest Patient Care
Explain test purpose and procedure. A strong positive result, that is, >3 on ELISA or ≥1:160 on IFA, may require follow-up testing of specific autoantibodies.
Follow guidelines in Chapter 1 for safe, effective, informed pretest care.
Posttest Patient Care
Review test results; report and record findings. Modify the nursing care plan as needed. Counsel the patient regarding abnormal findings; explain the need for possible follow-up testing and treatment.
SRDs, such as SLE, must be dealt with on a continuing basis and may require certain lifestyle changes. Repeat testing evaluates the effectiveness of therapy. Minor symptoms, in the absence of major organ involvement, are frequently treated with NSAIDs such as salicylates. Cutaneous manifestations respond to topical corticosteroid treatments. Short-acting corticosteroids, such as prednisone, are necessary if acute serologic changes and severe clinical manifestations appear.
Long-term moderate- to high-dose corticosteroids are central regimens prescribed for diffuse glomerulonephritis as well as RA.
Corticosteroid dosage may be reduced and kidney disease favorably managed by adding immunosuppressive drugs to the therapy regimen. Infection, secondary to immunosuppressive treatment, is a leading cause of death in patients with SRDs. Patient education plays a major role in prevention of infection.
Follow guidelines in Chapter 1 for safe, effective, informed posttest care.
Drugs, such as procainamide and hydralazine, may cause a positive ANA result.
Positive ANA levels may be found after viral illnesses and with some chronic infections.