Somewhere in the world today, a public health worker is administering a tuberculosis skin test using a protein first purified in a laboratory nearly a century ago — by a woman who, as a toddler in Easton, Pennsylvania, nearly lost the use of her legs to a different disease entirely, and who later said of her own career, ‘it never dawned on me that I was ever going to be considered important.’
Florence B. Seibert was a biochemist born in Easton on October 6, 1897, who went on to develop the purified protein derivative, known as PPD, that remains the worldwide standard for tuberculosis testing today. Decades earlier, she had already solved a separate, dangerous problem quietly killing patients in American hospitals.
At age three, Seibert and her older brother both contracted polio while playing together at home. Her brother recovered fully; Florence was left with a lifelong limp and years spent in leg braces. Undeterred, she graduated valedictorian of her Easton high school class and won a scholarship to Goucher College in Maryland, graduating in 1918 with a degree in chemistry and zoology. She spent the following years working as a chemist at a New Jersey paper mill before winning a second scholarship to Yale.
At Yale, Seibert pursued doctoral study in biochemistry, earning her Ph.D. in 1923 under advisor Lafayette Mendel. During her doctoral research, she discovered that dangerous, unexplained fevers following intravenous injections were caused not by the medicine itself but by bacterial contamination in ordinary distilled water used to prepare it. She invented a new distillation apparatus that eliminated the contamination entirely, and the design soon became standard equipment in hospitals across the country, quietly saving lives that had nothing to do with tuberculosis at all.
In 1932, Seibert joined the University of Pennsylvania's Henry Phipps Institute, recruited by researcher Esmond R. Long to work specifically on tuberculosis. A tuberculin skin test already existed, developed decades earlier by German bacteriologist Robert Koch, but its results were notoriously unreliable, since the biological extract behind it varied from one prepared batch to the next. Seibert set out to isolate the single active protein responsible for the immune reaction — a project that would occupy roughly a decade of her career, including a Guggenheim research fellowship in 1937 and 1938 at Sweden's University of Uppsala, where she worked alongside Nobel laureate Theodor Svedberg, refining the protein purification techniques she would need.
By the late 1930s, Seibert had succeeded, isolating and purifying that protein into what she called Purified Protein Derivative, or PPD. The United States adopted her exact PPD formulation as the official national standard for tuberculin testing in 1941. The World Health Organization adopted it as the international standard in 1952, and it remains the basis of tuberculosis testing performed around the world today, more than eighty years later.
Seibert's PPD test replaced decades of unreliable, wildly inconsistent tuberculosis screening with a single, reproducible standard that made early detection possible on a global scale, in a disease that had killed more people throughout history than almost any other. She built her career inside a scientific establishment with very few women in senior research positions, publishing dozens of papers over four decades and eventually retiring from the University of Pennsylvania as a full professor in 1958.
Seibert received the Trudeau Medal in 1938 and the Garvan Medal in 1942, and was inducted into the National Women's Hall of Fame in 1990, a year before her death in St. Petersburg, Florida, in 1991, at the age of ninety-three. A Pennsylvania historical marker stands today at her birthplace in Easton, commemorating both her tuberculosis research and her contributions to intravenous safety.
Information for this episode was gathered from Wikipedia’s Florence B. Seibert entry; Encyclopedia Britannica; Encyclopedia.com’s biographical entry, citing biographer Edna Yost; the Royal Society’s ‘Florence Seibert: From Polio Survivor to Medical Pioneer’; The Lancet Respiratory Medicine; and the Clio historical marker entry for Florence B. Seibert.
