What is the fine-grained topic of the following text: You will not have to visit any hospital to know whether you are HIV-positive or negative, thanks to US medical researchers who have developed a low-cost smartphone accessory that can perform a point-of-care test that simultaneously detects three infectious disease markers — HIV and syphilis — from a finger prick of blood in just 15 minutes. Only return the topic.
Development of a smartphone accessory for HIV and syphilis testing