Evaluation of clinical, laboratory, radiographical and histopathological characteristics in patients with spinal tuberculosis in the context of HIV infection: An analysis of 52 patients from a South African tertiary hospital.

Background: South Africa (SA) has the highest prevalence of people with tuberculosis (TB) and HIV coinfection globally. People living with HIV have an increased risk of TB infection, and are more likely to develop extrapulmonary TB. Approximately 10 - 20% of extrapulmonary TB accounts for skeletal TB, with spinal involvement in 50 - 60% of instances. Previous studies have shown highly heterogenic results regarding the effect of HIV status on clinical and laboratory characteristics in patients with spinal TB (STB).

Objective: To describe the clinical, laboratory, radiographical and histopathological characteristics of patients diagnosed with STB stratified by HIV status.

Methods: Data from patients who were treated for STB at the Division of Orthopaedic Surgery, Groote Schuur Hospital, SA, between 2013 and 2016 were analysed. We compared clinical, laboratory, radiographical and histopathological parameters of STB patients with HIV infection to those without HIV infection. To assess differences in means between the two groups, an independent samples t-test was used for normally distributed continuous data, and a χ2 test for categorical data. To assess correlations between continuous data groups, the Pearson correlation coefficient was used.

Results: We assessed 52 patients with STB (mean (standard deviation (SD) age 38 (15.2) years, range 17 - 80 years), of whom 55.8% were female, and 59.6% HIV infected. Five (9.6%) patients were identified with multidrug-resistant TB of the spine, with four (19.0%) in the HIV-infected cohort and one in the HIV-uninfected cohort (p=0.058). Significantly more STB patients without HIV infection presented with neurogenic symptoms (29%, p=0.029). The mean (SD) overall erythrocyte sedimentation rate was 69.3 (35.9) mm/h, with no significant difference between HIV-infected and HIV-uninfected patients (p=0.086). The rate of vertebral collapse was higher in the HIV-infected cohort (39% v. 67%, p=0.048). HIV-infected patients showed a higher count of involved vertebrae (mean 3.0 v. 3.85; p=0.034). There was no correlation between CD4 count and the number of involved vertebrae. The mean (SD) number of granulomata per low-power field was 10 (12.6), with no difference between the two cohorts. However, we found a positive correlation between granuloma count and CD4 cell count in HIV-infected STB patients (Pearson 0.503, p=0.02), with significantly higher formation of granulomata at a CD4 cell count >400 cells/μL (p=0.045).

Conclusion: In our cohort, HIV-infected patients with STB were more likely to present with vertebral collapse, and more vertebrae on average were diseased compared with HIV-uninfected patients with STB. CD4 cell count may affect granuloma formation, and it seems that HIV infection has a negative effect on cellular immunoresponse in STB, which emphasises the need for early antiretroviral therapy initiation.