A new study shows that people with glomerulonephritis (GN) are at significantly higher risk of experiencing active tuberculosis (TB) infections, at a rate 23 times higher than the general population. The results strongly suggest that patients should be screened for TB as soon as they receive their GN diagnosis.
Tuberculosis is a disease caused by mycobacterial infection, which most often affects the lungs. Many people who contract TB-causing mycobacteria can suppress the infection if their immune system is healthy. However, people with compromised immune systems are more likely to experience an activation of the infection later in life, which can potentially be life-threatening.
GN patients have a number of characteristics associated with a general increased risk of infection, including reduced kidney function, use of immunosuppressive medications, and having an autoimmune disease (GN is a type of autoimmune disease).
“So there were several reasons to think that GN patients would be at higher risk of active TB infections, but this hadn’t really been studied in GN patients,” explains Dr. Sean Barbour, a GN specialist with the University of British Columbia’s Division of Nephrology who led the recent study.
To gain a better understanding, Barbour partnered with experts at the BC Centre for Disease Control (BCCDC) to analyze population-level data. They looked at how many people diagnosed with GN were also treated with medications for active TB disease between 2000 and 2012, and then validated their approach using the TB database at the BCCDC.
A threshold used to define “high risk” of active TB infection is 30 cases per 100,000 human years. The results of this study led by Barbour, published in the American Journal of Kidney Disease, show that GN patients far exceed this threshold, at an average of 197 cases per 100,000 human years. This rate of active TB infections is approximately 23 times as high as the general population and more than six times higher than the threshold used to define high risk TB rates.
Some factors found to be associated with particularly higher TB risk included: immigration from a country with high incidences of TB infection, diminished eGFR, higher levels of protein in the urine, lupus nephritis, and use of immunosuppression medication.
However, all GN patients were found to be at high risk of TB infection, even if they were in the early stages of their kidney disease or not taking medications to suppress their immune system.
“What the results imply is that you should screen for TB in all GN patients at the time of biopsy when you’re making the diagnosis of GN, because you know then that patients are going to be high risk throughout the entire time of their disease course,” says Barbour.
