Depending on the outside temperature, the results of certain laboratory tests may vary which may affect what medications your doctor prescribes to you.
The results of laboratory tests performed in summer and in winter may vary. This is the hypothesis that two researchers, Ziad Obermeyer and Devin Pope, set out to test. Their work has just been published in the journal Med. According to them, this difference in results could have implications for medical decision-making, especially for drug prescribing. ‘When a doctor prescribes laboratory tests, he or she uses them to understand what’s happening inside your body, but we wondered if the results of these tests might also reflect something that’s happening outside your body,’ explains study co-author Ziad Obermeyer. It’s exactly the kind of pattern that doctors may not be aware of. and as a result, they may base their diagnosis and prescriptions on laboratory tests that are wrong.
Temperature affects more than 90% of individual tests
For their work, the researchers used the results of laboratory tests conducted between 2009 and 2015 in different climate zones. These included more than four million patients, two million of whom the researchers classified by temperature. This allowed them to measure how climate change affected these trials. According to their results, temperature affected more than 90% of the individual tests and more than 51% of other laboratory tests, including those for kidney function, cholesterol, or triglycerides, which are often measured in the blood as part of a lipid panel to assess cardiovascular disease risk.
Are fewer medications prescribed in the winter?
“These changes were minimal: in most experiments, the differences were less than one percent under normal temperature conditions,” says Ziad Obermeyer. Nevertheless, the researchers showed that lipids analyzed at lower temperatures showed lower cardiovascular risk, which was not the actual truth. Because doctors relied on these wrong tests, patients tested on cooler days were prescribed about 10% fewer drugs than patients tested on warmer days. In other words, a small number of people who needed treatment were not prescribed it because their laboratory tests were incorrect.
A call for temperature control in the laboratory
But why does temperature affect results? Researchers don’t have an answer at this point but propose several hypotheses: blood volume, the way specific tests are performed, the transport of samples, or even changes in laboratory equipment. Further research is needed to verify these. “Whatever the cause, temperature introduces unwanted variability into certain tests, which can interfere with some important medical decisions,” emphasizes Devin Pope, co-author of the study. One solution the authors suggest is for labs to adjust room temperature on the day of the test. This is a low-cost method of reducing variability due to weather conditions.