Background: The diagnosis of central nervous system (CNS) lymphoma in HIV-positive patients is a clinical challenge. Failure to the empirical treatment for toxoplasma encephalitis is often followed by brain biopsy. However, this strategy is associated with a delay in diagnosis and worse prognosis. The utility of Thallium-201 SPECT scan (201Tl-SPECT) in the diagnosis of CNS lymphoma has been poorly explored. We sought to analyze its diagnostic accuracy in a cohort of HIV-positive patients at a tertiary-care center in Mexico City.
Methods: Retrospective cohort study (Jan 2011- Dec 2017). We included all HIV-positive adults with focal CNS lesions (CT or MRI) in whom a 201Tl-SPECT was performed. We retrieved clinical, laboratory and imaging data from hospital medical records. Final diagnoses were established by brain biopsy (4), clinical response to anti-toxoplasmosis therapy (4), or clinical course (5). All the 201Tl-SPECT images were reviewed by a radiologist who was blind to the final diagnosis.
Results: We included 13 patients, 100% males with a median age of 35 yr (Range 26-63), the median CD4+ count and viral load were 68 cells/µl (Range 4-224) and 365,199 copies/ µl (Range 40-2,109,395) respectively. 35% presented a single CNS lesion, the remainder 65% presented more than one. 46% presented an increased thallium uptake on SPECT scan, 50% of them were diagnosed with CNS lymphoma. The remainder 50% corresponded to a case of CNS toxoplasmosis and a patient with Balamuthia spp encephalitis. We also found that 83% of these patients with a positive 201Tl scan had a positive EBV PCR viral load on CSF (range 34-5,330 copies/ml). Among the 54% patients who did not show an increased uptake on Tl-SPECT, 42% were diagnosed with CNS toxoplasmosis, and one patient was diagnosed with a CNS lymphoma. The overall 201Tl-SPECT sensitivity, specificity, positive predictive value, and negative predictive value for the diagnosis of CNS lymphoma were 75% (CI95% 19.4-99.3), 75% (CI95% 34.9-96.8), 60% (CI95% 28.4-84.9), and 85.7% (CI95% 51.2-97.1), respectively.
Conclusion: 201Tl-SPECT had a limited screening and diagnostic accuracy for primary SNC lymphoma. More studies are needed to corroborate these findings.
M. Muñoz Lopez,
R. Martinez-Martinez, None
L. E. Soto Ramírez, None