This invention uses a paper-based immunoassay to identify TB. Capturing dilute target molecules remains a challenge in engineering diagnostic immunoassays. One way to overcome this challenge is to use a great excess of binding molecule to create pseudo first-order reaction conditions that can then efficiently capture nearly all target molecules in a sample. These inventors developed a bifunctional protein containing a domain to bind the urine TB biomarker Rv1656 and another domain that tightly binds cellulose. The cellulose-binding domain is used to anchor a high concentration of the bifunctional protein onto paper and the paper bound protein can capture nearly all Rv1656 from a dilute solution. Importantly, this protein can be rapidly produced and purified using bacterial culture systems.