![]() ![]() The kit included a needle and glass capillary tubes for collecting blood from the earlobe, a bottle of salt solution for diluting the sample, a bottle of killed typhoid bacilli suspension, dropper bottles, test tubes, and a rack. By 1912, the Mulford company was advertising a complete test outfit based on his modifications. ![]() In 1905, bacteriologist John Borden modified the Widal test in a way that freed practicing physicians from their reliance on the services of bacteriological laboratories. If the cells clumped together, the patient had typhoid antibodies, which indicated either current infection or prior exposure to the disease. He mixed a small sample of the patient’s blood serum with a suspension of typhoid bacilli, then used a microscope to examine a drop of the solution. Widal devised a practical diagnostic technique for typhoid based on this phenomenon. The clumps were easily observed through a microscope. This clumping, called agglutination, resulted from the binding of antibodies in the blood serum to the bacterial antigens. Scientists had observed that cholera bacteria would clump together when injected into animals that had been immunized against the disease. In 1896, French physician and bacteriologist Georges Fernand Isidore Widal introduced a blood test for typhoid that still bears his name. In recent years, the increase of point-of-care diagnostic devices has allowed more testing to move out of the laboratory and into the clinic or home.Įach of the following tests has had an enormous influence on how individuals and communities have chosen to control, prevent, and treat disease. Rapid screening tests that can be used in the field are often backed up by more extensive laboratory-based tests. Factors such as cost, speed, and ease-of-use influence the design of testing methods and devices. Scientists, doctors, and public health workers employ tests for different purposes. Repeat testing and different techniques can give conflicting results. Diagnostic tests continue to influence our understanding of disease and how we define the borders between sickness and health.Įven the most accurate tests are imperfect. Testing could reveal infections before outward symptoms appeared and helped identify disease “carriers”-individuals who remained symptomless but nonetheless could spread disease. These tests revealed information about the patient’s disease history, including both on-going infections and prior exposure to disease. Scientists devised tests to detect the presence of antibodies in blood and employed antigens to provoke an immune response. The new tools emerged from a growing understanding of the immune system and the role played by antitoxins (antibodies) that the body produced in response to invading organisms or toxins (antigens). Beginning in the late 19th century, scientists investigating infectious disease developed new diagnostic techniques along with new therapies. Accurate medical diagnosis is a critical first step for determining individual treatments, as well as for tracking the spread of disease and establishing effective public health strategies. ![]()
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