What tests are used to diagnose SLE psychosis?

Diagnostic Tests for SLE Psychosis

To rule out SLE psychosis, a comprehensive diagnostic workup including brain MRI, CSF analysis, EEG, and specific antibody testing should be performed to exclude non-SLE causes and confirm SLE-related psychosis. 1

Primary Diagnostic Tests

Brain Imaging

• Brain MRI: Essential first-line test with modest sensitivity (50-70%) and specificity (40-67%) for lupus psychosis 1
  • Recommended protocol: conventional MRI sequences (T1/T2, FLAIR), diffusion-weighted imaging (DWI), and gadolinium-enhanced T1 sequences
  • Purpose: To exclude structural brain disease and detect any inflammatory changes

Laboratory Tests

• Cerebrospinal fluid (CSF) analysis:

  • Critical to exclude CNS infection and other non-SLE causes 1
  • Look for mild-to-moderate abnormalities (present in 50-70% of cases)
  • Include microbiological studies to rule out infectious causes

• Antibody testing:

  • Anti-ribosomal P antibodies: Associated with psychiatric SLE in prospective studies, though with limited diagnostic accuracy (sensitivity 25-27%, specificity 75-80%) 1
  • Antiphospholipid antibodies: Strong risk factor for primary NPSLE 1

Neurophysiological Tests

• Electroencephalography (EEG):
  • Helps diagnose underlying seizure disorders that may accompany psychosis 1
  • May show nonspecific abnormalities in SLE psychosis

Differential Diagnostic Considerations

Steroid-Induced Psychosis vs. SLE Psychosis

• Steroid-induced psychiatric disease occurs in 10% of patients treated with prednisone ≥1 mg/kg 1
• Key differentiating factors:
  • Steroid-induced psychosis manifests primarily as mood disorder (93%) rather than true psychosis 1
  • Prompt response to reduction in steroid dose suggests steroid-induced psychosis 2
  • Presence of generalized SLE activity suggests SLE-related psychosis 1

Other Considerations

• Brain SPECT: Identifies perfusion deficits in severe cases (80-100%); residual hypoperfusion during clinical remission correlates with future relapse 1
• Exclude metabolic causes: Evaluate for electrolyte disturbances, uremia, and other metabolic abnormalities

Diagnostic Algorithm

1. Initial evaluation:

   • Assess for focal neurological signs, altered mental status, and generalized SLE activity
   • Check for fever or concomitant infection that might suggest alternative causes

2. First-line tests:

   • Brain MRI with recommended protocol
   • CSF analysis with microbiological studies
   • EEG to exclude seizure disorders
   • Antibody panel (anti-ribosomal P, antiphospholipid antibodies)

3. Additional tests based on clinical presentation:

   • Brain SPECT if available and initial tests inconclusive
   • Neuropsychological assessment if cognitive dysfunction is suspected

Common Pitfalls and Caveats

• Misdiagnosis risk: SLE psychosis can be mistaken for primary psychiatric disorders, especially when it presents before other SLE manifestations 3
• Treatment resistance: Psychotic symptoms resistant to conventional antipsychotic treatment should raise suspicion for SLE psychosis 3
• Steroid confusion: Steroid-induced psychosis is rare but can complicate the diagnosis; occurs more frequently in patients with hypoalbuminemia and high-dose steroids (0.75-1 mg/kg/day) 4
• Recurrence risk: Recurrence of primary psychosis is associated with other CNS manifestations related to SLE 4

Conclusion

The diagnosis of SLE psychosis requires a systematic approach to exclude non-SLE causes and confirm SLE-related psychosis. Brain MRI, CSF analysis, and antibody testing form the cornerstone of the diagnostic workup. The presence of generalized SLE activity, response to immunosuppressive therapy, and specific antibody profiles can help differentiate SLE psychosis from other causes of psychosis.