Medicines can distort the results of laboratory tests – both by disrupting the measurement and affecting the condition of the body – said specialists at the Wednesday conference organized by the Office for Registration of Medicinal Products, Medical Devices and Biocidal Products.
The conference was held as part of the Lek Bezpieczny campaign.
Modern laboratory medicine is no longer dismissively referred to as the + auxiliary + field, and research as + additional + – said Hanna Hausner from the National Council of Laboratory Diagnosticians. She added that in many cases the obtained results are decisive.
Hausner recalled that laboratory medicine was divided into several subspecialties, for example: laboratory hematology, toxicology and virology. Most of the tests are carried out automatically, using complicated equipment, and the volume of the tested sample is sometimes measured in microliters, she said.
Medicines can influence each other’s effects, so it is no wonder that sometimes they also change the results of laboratory tests – said Dr. Monika Jabłonowska from the Central Analytical Laboratory of the Provincial Infectious Hospital in Warsaw.
According to Dr. Jabłonowska, the pharmacological effect itself, both desirable and undesirable, influences, for example, the content of sodium or potassium in the blood – an example may be diuretics. Some drugs inhibit blood cell production, others interfere with the liver. An extreme example was a suicide in which, under the influence of a huge dose of paracetamol, the concentration of liver enzymes exceeded the norm about a hundred times. Drugs such as aspirin can reduce blood clotting, which affects the appropriate tests, she said.
Some drugs also work physicochemically – they disrupt the chemical reactions used in diagnostics, interact with biological material or a reagent. An example is ascorbic acid excreted in the urine, i.e. ordinary vitamin C, which changes the results of many studies – said Dr. Jabłonowska.
Manufacturers try to prevent such situations, for example, by adding an enzyme that breaks down ascorbic acid to the reagents. They also publish lists of drugs along with the corrections to be made when testing the samples.
Some changes are easy to spot for yourself. Cimetidine and promethazine turn urine green, amitriptyline – bluish, daunorubicin – red, rifampicin orange, and iron preparations – black.
Dr. Jabłońska emphasized that alcohol definitely influences the research results. In many cases, it was found that a positive HIV or viral hepatitis test was a false alarm, caused by the effects of a recent wedding. It is true that the result in such cases was weakly positive, but it was still necessary to perform another control test, which meant a lot of stress for the patient. That is why it is not worth doing research the day after the grand party – said the specialist.
Properly performed and interpreted examination is a valuable help for the doctor and the patient. Unfortunately, even several dozen percent of research results remain unclaimed. In order for the result to be fully reliable, it should also mention the name of the responsible specialist as well as the method and brand of equipment used – added Dr. Jabłonowska. (PAP)