In a 26-year-old woman with systemic lupus erythematosus on low-dose glucocorticoids and hydroxychloroquine, which laboratory test is most appropriate to assess current disease activity?

Laboratory Testing for SLE Disease Activity Monitoring

Anti-dsDNA antibody titer (option c) is the most appropriate laboratory test to assess current disease activity in this patient with established SLE on maintenance therapy. 1, 2

Rationale for Anti-dsDNA Testing

Anti-dsDNA antibodies serve as a key serological marker for monitoring disease activity in SLE patients:

• Serological activity (anti-dsDNA and low complement) is consistently reported as a risk factor for higher disease flare rates, making anti-dsDNA monitoring essential for disease surveillance 1

• EULAR guidelines specifically recommend assessing complement levels (C3, C4) and anti-dsDNA antibodies to evaluate disease activity in lupus patients 2

• Anti-dsDNA levels should be monitored serially (every 3 months during active monitoring) to track treatment response and predict flares 3

• Patients with high anti-dsDNA titers (>300 IU/mL) demonstrate higher disease activity and require more aggressive immunosuppression 3

Why Other Options Are Less Appropriate

ANA titer (option a) is not useful for monitoring disease activity:

• ANA remains positive in the vast majority of SLE patients regardless of disease activity status 1
• ANA is a diagnostic test, not a monitoring tool for established disease

Complement C10 (option b) is not a standard test:

• This appears to be an error; complement C3 and C4 (not C10) are the relevant tests
• While complement levels are useful, they should be assessed alongside anti-dsDNA for comprehensive monitoring 2, 3

Anti-Smith antibodies (option d) are not useful for activity monitoring:

• Anti-Smith antibodies are highly specific for SLE diagnosis but do not fluctuate with disease activity 3
• These antibodies remain relatively stable over time and are not recommended for serial monitoring

Clinical Application

For this 26-year-old woman on maintenance therapy with low-dose steroids and hydroxychloroquine:

• Monitor anti-dsDNA titers along with complement levels (C3, C4) to assess serological activity 1, 2

• Rising anti-dsDNA titers or falling complement levels indicate increased risk of flare, even before clinical symptoms emerge 1

• The presence of serologically active clinically quiescent (SACQ) disease—elevated anti-dsDNA or low complement without clinical symptoms—is an independent risk factor for future flares 4