CRP, ferritin levels may distinguish patients with positive sputum cultures 60 days after ATT
Circulating levels of C-reactive protein (CRP) and ferritin are elevated in patients with tuberculosis (TB) starting antituberculosis therapy (ATT) and decrease over time, a new study shows. However, those that still had positive cultures after 60 days of ATT show elevated levels of these markers.
The longitudinal cohort study involved 165 pulmonary (75.7 percent male; median age 40 years) TB patients initiating ATT and between the ages of 18 and 60. Those who were taking antituberculosis medication, had type 1 diabetes mellitus, renal failure, were receiving peritoneal or haemodialysis, and pregnant were excluded.
Cryopreserved serum samples were used to measure serum levels of CRP and ferritin. Sputum samples were also collected from participants and were assessed for the respective mycobacterial loads. The associations between these parameters and sputum conversion at 60 days after ATT were evaluated.
Among all the comorbidities, anaemia (75 percent), HIV/AIDS (10 percent), type 2 diabetes (3 percent) and chronic obstructive pulmonary disease (3 percent) were the most common. Active smoking, chronic alcoholism and illicit drug use were reported in 73, 59.4 and 28.5 percent, respectively, of the study population.
Prospective analysis showed a drop in CRP levels from day 0 to day 30 of ATT (p<0.001); this trend continued to day 60 but was not significant. Levels of ferritin at day 60 was significantly reduced compared to its levels at day 0 (p<0.001) and day 30 (p<0.05). Ferritin and CRP were significantly correlated at pretreatment (p<0.0001), day 30 (p=0.001) and day 60 (p<0.0001).
Patients with negative sputum cultures at day 60 of ATT showed a decreasing trend in the levels of ferritin and CRP (p<0.0001 for both). On the other hand, those that had positive cultures showed a slight decreasing trend in ferritin levels (p=0.0041) and no significant trend in CRP levels.
Finally, levels of CRP (p=0.0005) and ferritin (p=0.002) were significantly greater in patients with positive sputum cultures than those with negative sputum cultures at day 60.