Scientists use finger sweat to track drugs in bloodstream with 96% accuracy

A new study from the University of Surrey aimed at tuberculosis detected antibiotics in the bloodstream using fingerprint sweat with almost the same accuracy as a blood test.

Tuberculosis is among the leading causes of death from an infectious agent, a new study opens, with an estimated 1.3 million deaths worldwide in 2022. Drug-susceptible tuberculosis, however, is curable. However “approximately 50% of patients do not fully adhere to their prescribed lengthy regimen of antibiotics.”

In these cases, monitoring a patient’s treatment becomes crucial as any deviation from their prescription plan might inhibit its effectiveness and could lead to drug-resistant TB instead.

Scientists at the University of Surrey wanted to close this much-needed gap. They conducted a study to evaluate the best time to test for drugs in the bloodstream and determine how much medication a patient has taken.

First, why finger sweat?

Professor Bailey told Interesting Engineering that they decided to work with finger sweat due to their work in forensics. The study “explores what intelligence can be gained by analyzing the chemical composition of a fingerprint left at a crime scene.”

“A fingerprint is a convenient sample to take in clinical testing as it’s completely painlessly and non-invasively, without any loss of dignity from the patient.”

Professor Bailey’s team collected blood, saliva, and sweat samples from patients in hospitals during the COVID pandemic. While collecting blood and saliva proved challenging, they never had a problem collecting sweat.

They applied this insight to their most recent study into tuberculosis treatment. They gathered a sample pool of ten TB patients at the University Medical Center Groningen (UMCG) in the Netherlands.

“It was very simple to collect our samples,” Dr. Onno Akkerman from UMCG said.

“We asked patients to wash their hands, put on a nitrile glove to induce sweating, and then press their fingertips onto a paper square.”

A study on ten tuberculosis patients proved sweat a promising method

Scientists detected antibiotics and the metabolite produced by ingesting the drug with 96 percent and 77 percent accuracy, respectively. They were able to identify the presence of the drug “between one to four hours after ingestion while the metabolized version showed up best after six hours.” So the best time to test, their data suggests, would be 1-6 hours after ingestion of the drug.

Such information being the tips of doctor’s fingerprints stands to impact tuberculosis which follows a strict treatment plan.

“Doctors need to check whether tuberculosis patients are taking their antibiotics, Dr. Katie Longman, co-author of the study, reiterated. “It’s much quicker and more convenient to do that using fingerprints rather than blood.”

Sweat isn’t a biohazard like blood

Blood sampling requires specialist training and handling as blood is a biohazard due to its capacity to transmit disease. On the contrary, collecting fingerprint sweat can be performed without the need for special parameters even around transportation and storage.

“This could ease the time pressure on a busy health service and offer patients a more comfortable solution,” Dr. Longman continued, as “blood tests are not feasible or desirable” in many cases. This novel technique could be really useful moving forward, she said in a press release .

“Up until now, blood tests have been the gold standard for detecting drugs in somebody’s system,” Professor Melanie Bailey said. “Now we can get results that are almost as accurate through the sweat in somebody’s fingerprint.”

Many potential avenues come to mind for this noninvasive method of tapping into the bloodstream including improved drug delivery and retention which could impact the development of pharmaceuticals if not diagnostics, according to Professor Bailey, as well as tests for illicit substance use.

“We have done quite a lot of work in the past to monitor cocaine and other illicit drugs in fingerprints,” Professor Bailey said. “The forensic interpretation of finding drugs in a fingerprint is much more complex,” however.

“Hands are not washed before leaving a trace. In therapeutic drug monitoring, we have the luxury of being able to wash hands before giving a sample.”

“Up until now,” she concludes, “the samples have been used to provide a purely qualitative (yes/no) answer on drug use, rather than giving a level. It is particularly exciting that our study has shown a correlation between blood and finger sweat as this shows the potential for quantitative analysis.”

The study is published in the International Journal of Antimicrobial Agents .