Serum chitotriosidase activity in South African patients with sarcoidosis and tuberculosis

Chitotriosidase is a chitinase enzyme that is expressed selectively through activated macrophages in humans. Increased activity of chitotriosidase in both bronchoalveolar lavage samples and serum of patients with sarcoidosis has been reported. It has been proposed that chitotriosidase could be used as a potential biomarker for diagnosis, monitoring and prognosis in sarcoidosis patients. However, no studies in a South African (SA) cohort have evaluated this potential role.

To analyse serum chitotriosidase activity in treated and untreated sarcoidosis patients, healthy controls and patients with tuberculosis (TB). Sarcoidosis and TB are two diseases of differing aetiology that may be clinically difficult to distinguish between in the SA setting, which is a high-burden area for TB. We hoped to determine whether chitotriosidase activity levels could help differentiate the one disease from the other.

Serum chitotriosidase activity was measured in an SA cohort of treated and untreated sarcoidosis patients and compared with controls. In addition, activity in sarcoidosis patients was compared with that in TB patients. Overall, chitotriosidase activity was assayed in the serum of 12 biopsy-proven sarcoidosis patients before treatment, 9 sarcoidosis patients after at least a month's treatment, 10 patients with confirmed pulmonary and/or disseminated TB before treatment, and 12 healthy controls. Plasma chitotriosidase activity was assayed as previously described using 4-methylumbelliferyl-β-D-N,N',N″-triacetylchitotriose as a substrate.

Significantly higher serum chitotriosidase activity was observed in sarcoidosis patients, both untreated and treated, compared with controls (p<0.05). Sarcoidosis patients had higher chitotriosidase levels than TB patients, but this difference was not significant. While chitotriosidase activity was lower in patients with TB than in those with sarcoidosis, levels were elevated compared with controls.

Chitotriosidase activity in patients with sarcoidosis was greater than in those with TB, and also greater compared with controls. The increased chitotriosidase activity in sarcoidosis suggests that this enzyme may be involved in the disease pathogenesis. Further investigation is required to validate these findings.

What the study adds. Serum chitotriosidase activity in South African sarcoidosis and tuberculosis (TB) patients was evaluated. The study adds to the research assessing the significance of serum chitotriosidase in patients with sarcoidosis and TB.Implications of the findings. Chitotriosidase enzyme activity could potentially serve as a biomarker of possible diagnostic and/or prognostic value in patients with sarcoidosis.