Using a fingerprint for non-invasive drug monitoring
Scientists have developed a new way to measure drug levels in sweat from a fingerprint, offering a non-invasive alternative to blood sampling.
Through their continuous work on fingerprint sampling, a research group from the University of Surrey (UK) collaborated with scientists from the University of Groningen (the Netherlands) to devise a non-invasive ‘fingerprint’ method to monitor therapeutic drugs from the finger sweat of tuberculosis (TB) patients.
TB is one of the top causes of deaths due to infectious diseases, resulting in about 1.3 million deaths globally in 2022. Although drug-susceptible type TB is treatable, around 50% of patients fail to complete the full course of prescribed antibiotics. For effective treatment, patients need to follow their prescriptions diligently. Therefore, it is recommended in routine TB care to conduct therapeutic drug monitoring (TBM), by evaluating drug exposure levels and making necessary dosage adjustments.
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TDM is typically carried out on blood samples (serum or plasma), but less invasive sampling methods such as dried blood spots and saliva have been suggested. The current study explored another less invasive alternative: finger sweat.
“It was very simple to collect our samples. We asked patients to wash their hands, put on a nitrile glove to induce sweating, and then press their fingertips onto a paper square. Finger sweat can be collected without any specialist training. Unlike blood, it isn’t a biohazard, so can be transported and stored much more easily,” explained Onno Akkerman, a Pulmonary physician from the University of Groningen.
Researchers assessed the use of finger sweat as a tool for medication adherence of isoniazid, a frontline anti-TB antibiotic. They determined the optimum time after dosing to collect samples for a non-invasive adherence test was 1–6 hours post-dose, with a detection rate of 96% and 77% for isoniazid and acetyl isoniazid (a metabolite of isoniazid).
Moreover, they compared the mass of isoniazid and acetyl isoniazid in finger sweat samples with traditional samples, such as blood and saliva, and also accounted for sample volume inconsistencies by measuring the mass of creatinine (an endogenous compound found in both sweat and blood). The researchers discovered that the performance of the finger sweat method was comparable with blood sampling, with no correlation between the mass of isoniazid in finger sweat compared to isoniazid concentration in blood serum or saliva.
“Up until now, blood tests have been the gold standard for detecting drugs in somebody’s system. Now we can get results that are almost as accurate through the sweat in somebody’s fingerprint. That means we can monitor treatment for diseases like tuberculosis in a much less invasive way,” commented the leading scientist, Melanie Bailey, from the University of Surrey.
The group believes this ‘fingerprint’ method has potential applications in other prominent therapeutic medications, existing as an attractive, convenient alternative for non-invasive drug testing.
“Doctors need to check whether tuberculosis patients are taking their antibiotics. It’s much quicker and more convenient to do that using fingerprints rather than taking blood. This could ease the time pressure on a busy health service and offer patients a more comfortable solution. For some patients, like babies, blood tests are not feasible or desirable—so techniques like this one could be really useful,” commented Katie Longman, a Postgraduate Research Student from the University of Surrey.
