Risk for TB Infection Predicted by New Scoring System

Advances in diagnosing and treating pulmonary tuberculosis (TB) have gone a long way toward improving the outlook for people who get the disease. But to eradicate TB worldwide, preventing new infections in high-risk groups still needs to be better addressed. Researchers at Imperial Collge London in the United Kingdom, and colleagues, have developed a tool that can help, according to a study published in The Lancet: Infectious Diseases — a scoring system to predict who is most likely to get the disease after contact with someone who has it.

The researchers used health information from 715 cases of pulmonary TB and 2017 adults 15 and older who had contact with them who were living in desert shanty towns in Peru. They also used certain risk factors for TB: body-mass index, previous TB infection, age, sustained exposure to someone with confirmed TB, the confirmed TB patient being male, low household socioeconomic position, indoor air pollution, previous TB infection in household members, and living in a house with a limited number of windows per room.

A proportional hazard model was applied to the data to create a scoring system for predicting 10-year risk for getting TB after contact with the infected person. The score was later validated in a different urban community in Peru.

The fact that the score was able to be validated separately in a different community showed that ranking based on the 9 clinical and demographic risk factors could accurately identify  those populations most at risk for the disease. According to the risk score, a person with no history of TB with low exposure, who is well nourished, and living in a well-ventilated home may have a 10-year predicted risk of 1 in 100.  A person with a history of TB with high exposure, who is underweight, and lives in a poorly ventilated home may have a 10-year predicted risk of 1 in 3.

Having an accurate score for predicting infection can be useful, the researchers point out, not just for identifying who is at risk for TB, but for ranking the degree of risk — so that interventions can be better targeted to protect persons living near or with someone known to have the disease. 

Reference

Saunders MJ, Wingfield T, Tovar MA, et al. A score to predict and stratify risk of tuberculosis is adult contacts of tuberculosis index cases: a prospective derivation and external validation cohort study [published online August 18, 2017]. Lancet Infect Dis. doi:10.1016/S1473-3099(17)30447-4