Diagnostic Approach for Ruling Out SLE and Thyroiditis
To rule out Systemic Lupus Erythematosus (SLE) and thyroiditis, perform comprehensive laboratory testing including autoantibody panels, thyroid function tests, and appropriate clinical assessments. 1, 2
Laboratory Testing for SLE
- At baseline, test for the following autoantibodies and complement levels: ANA, anti-dsDNA, anti-Ro, anti-La, anti-RNP, anti-Sm, anti-phospholipid antibodies, C3, and C4 1
- Complete blood count, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), serum albumin, serum creatinine (or eGFR), urinalysis, and urine protein/creatinine ratio should be performed at 6-12 month intervals in patients with inactive disease 1
- Re-evaluate previously negative patients for anti-phospholipid antibodies prior to pregnancy, surgery, transplant, use of estrogen-containing treatments, or in the presence of new neurological or vascular events 1
- Re-evaluate anti-Ro and anti-La antibodies before pregnancy 1
- Anti-dsDNA, C3, and C4 may support evidence of disease activity or remission 1
Laboratory Testing for Thyroiditis
- Test for thyroid function including T3, T4, and TSH levels 3, 2
- Test for thyroid autoantibodies including thyroid peroxidase antibodies (TPOAb) and antithyroglobulin antibodies (ATGAb) 3, 2
- Consider the presence of euthyroid sick syndrome, which is found in approximately 11.1% of SLE patients 2
Clinical Assessment for SLE
- Evaluate disease activity using a validated index at each visit 1
- Assess for mucocutaneous lesions and characterize them as LE-specific, LE non-specific, LE mimickers, or drug-related 1
- Monitor for neuropsychological symptoms including seizures, paresthesiae, numbness, weakness, headache, epilepsy, and depression through focused history 1
- Assess cognitive function by evaluating attention, concentration, word finding, and memory difficulties 1
Clinical Assessment for Thyroiditis
- Evaluate for symptoms of hypothyroidism (fatigue, weight gain, cold intolerance, constipation) or hyperthyroidism (weight loss, heat intolerance, tremor, anxiety) 2
- Be aware that SLE patients have a two-fold increased risk of Hashimoto's thyroiditis compared to the general population 4
- Note that thyroid dysfunction is significantly increased in SLE patients (50%) compared to other autoimmune conditions like RA (15%) 3
Renal Assessment for SLE
- For patients with persistently abnormal urinalysis or raised serum creatinine, obtain urine protein/creatinine ratio (or 24h proteinuria), urine microscopy, and renal ultrasound 1
- Consider referral for kidney biopsy in patients with abnormal renal findings 1
- For established nephropathy, monitor protein/creatinine ratio (or 24h proteinuria), immunological tests (C3, C4, anti-dsDNA), urine microscopy, and blood pressure at least every 3 months for the first 2-3 years 1
Important Considerations
- Thyroid autoantibodies may precede the appearance of clinical autoimmune thyroid disease in 70% of SLE patients 5
- Symptoms of SLE and thyroid disease can overlap, making diagnosis challenging 5
- Subclinical thyroid disease is identified in approximately 11.5% of SLE patients 5
- The presence of Sjögren syndrome and positive rheumatoid factor are more frequently observed in SLE patients with autoimmune thyroid disease 5
- Disease activity of SLE may correlate with symptoms of hyperthyroidism 5
Pitfalls to Avoid
- Do not rely solely on ANA testing for SLE diagnosis, as it can be positive in other conditions 1
- Do not dismiss the possibility of thyroid disease in SLE patients with nonspecific symptoms that could be attributed to either condition 5
- Do not overlook the need for regular monitoring of thyroid function in SLE patients, even if initially normal 2, 5
- Remember that hypothyroidism is more common than hyperthyroidism in SLE patients 3, 2
By following this comprehensive diagnostic approach, you can effectively rule out or confirm the presence of SLE and thyroiditis, leading to appropriate management and improved patient outcomes.