Drugs that interfere with the results of laboratory tests: an integrative review of the literature

Medicamentos que interferem nos resultados de exames laboratoriais: uma revisão integrativa da literatura


Sandna Larissa Freitas dos Santos1

Romênio Nogueira Borges2

Karla Bruna Nogueira Torres Barros3


1Graduada em Farmácia pelo Centro Universitário Católico de Quixadá – Quixadá-CE, Brasil.

2Discente do curso de Farmácia pelo Centro Universitário Católico de Quixadá Quixadá-CE, Brasil.

3Farmacêutica, Docente do Curso de Farmácia pelo Centro Universitário Católico de Quixadá –Quixadá-CE, Brasil.


Instituição: Centro Universitário Católico de Quixadá – Quixadá-CE, Brazil.


Recebido em 15/05/2017

Artigo aprovado em 12/04/2018

DOI: 10.21877/2448-3877.201800581



Objective: To gather scientific knowledge about the use of drugs that cause interference in the results of laboratory tests. This is an integrative review of the literature that used Lilacs, SciELO and Medline as databases and to search for articles; the keywords in Portuguese and English were selected using Bireme’s (DeCS) tests: tests Laboratory interactions, drug interactions and interferences. Research published in English, Portuguese or Spanish was published in the form of articles, reviews, dissertations and theses published between 2009 and 2016. Interference caused by medication is a major problem because the patient may be in use of several prescribed drugs, and mainly by self-medication. Among the most commonly used medications, paracetamol causes an increase in alkaline phosphatase and bilirubin, as well as some corticosteroids, such as hydrocortisone that elevates chlorine through salt and water retention. In hematological examinations the reduction of erythrocytes can be provoked by the use of acyclovir, amitripilina, captopril, cimetidina or levodopa. It emphasizes the importance of an effective clinical evaluation of the patient, so that the use of medicines is seen and thus, guarantee quality in the results of the laboratory tests.



Laboratory; Laboratory test; Drug




A quality test result depends on the success of all processes involving the laboratory examination, since the collection of material to review and release the result. In the study of metabolism and the action of drugs in the body, it is known that this process leads to some changes in the organic operation itself and also produce metabolites (active or not). The metabolites have the aid of the circulatory system for transport (on excretion and/or site of action) of the urinary system (on excretion), among other systems.(1)

In laboratory diagnostic tests used in most cases of blood and urine, the tests search the type and quantity of substances that indicate or quantify for definition of the diagnosis of a particular disease. These substances and medicines are chemical origin and often resemble in structure. The diagnostic equipment and even chemical reagents using this information to identify and quantify, although not so accurate to differentiate them. Thus, any medicine can be identified as another substance, leading to an erroneous result.(2)

The verification of the quality of the sample according to the material and the tests requested by the doctor is extremely important, because pre-analytic factors may interfere in the results significantly such as medicine, hemolysis, lipemia, hyperbilirubinemia, collection time, practice, time of fasting, alcohol consumption and cigarette use.(3)

It is worth mentioning that the drugs interferes with the harmonious organic operating during the period of use or prolonged use, which this lack of control can also lead to altered lab results, positively or negatively. With that, a high consumption of drugs by the population with both order preventive as the most diverse pathologies, dressing andyess, the study aims to present the drugs that cause interference results in the context of the webbing.



Material and methods


The present study uses as integrative literature review method, which presents the objective to gather and summarize scientific knowledge already provided on the use of medicines that cause interference on the results of laboratory tests, allowing to evaluate and condense the evidence available in order to contribute to the development of knowledge on the subject.

For the development of this integrative review the following steps were covered: defining the guiding question (problem) and aims of research; establishment of criteria for inclusion and exclusion of publications (sample selection); Search in the literature; analysis and categorization of studies, presentation and discussion of results.(4) To guide the research, formulated the following question: what medicines cause interference on the results of laboratory tests?

The search was conducted in the following databases: Latin American literature and Caribbean Health Sciences (Lilacs), electronic library Scientific Electronic Library Online (SciELO), Medline – Medical Literature Analysis and Retrieval System online and VHL – Virtual Health Library. For the search of the articles were used keywords in Portuguese and English selected by consulting the health sciences descriptors (DeCS) of Bireme: laboratory tests, drug interactions and interference. Inclusion criteria were: research that cover the use of medications that cause interference in laboratory results, types of these interactions and approaches of innovations, which were published in English, Portuguese or Spanish; in the form of articles, reviews, dissertations and theses published from 2009 to 2016. As exclusion criteria: jobs that do not submit abstracts in their entirety in the databases and the library surveyed, it was in previous years and publications with duplicity.

The productions that established the criteria were selected for this study, and analyzed in their entirety. And so, proceeded with the analysis and organization of publications, in order to describe the results, showing the knowledge produced on the theme proposed.




The laboratory tests that are used for several purposes in diagnosis of diseases, provide results should be interpreted with the concomitant problems identified in the clinical evaluation of the patient. Thus, the decision of the medical clinic with the help of the examination, confirms or excludes the diagnosis, and thus, set the appropriate therapeutic alternative. In addition, the test can also be used in diagnostic monitoring, that is, the professional has the monitoring of therapy and the development of Pathology.(1)

However, there is no absolutely precise examination, several factors that may interfere with test results such as: patient preparation (such as time of day, fasting or fed, drug injection, smoking), the sample collection form (such as venipuncture method, suitable for collection, identification of the sample), the sample handling (transport, processing, storage), analysis (such as accuracy of the method , accuracy of the method, automation), the issue of the results (with erroneous calculations, printed or verbal communication without clarity), effect of medicines.(5)

The interference caused by medicines constitutes a big problem, because the patient may be in use of multiple prescription drugs, and especially by self-medication. These drug interference can be divided into: in vivo physiological effects of the drug and its metabolites, and in vitro effects resulting from a physical-chemical property in analytical processes.(6,7) Table 01 presents examples of various medicines with their respective changes in laboratory tests.

The in vivo physiological effects can manifest themselves when the drugs induce lesions in tissues or organs, such as the anfoterencina B-induced Nephrotoxicity by medicines that alter organ functions such as simvastatin that increases levels of alanine aminotransferase and aspartate aminotransferase, by the effect of competition for medicines, as the offset of the thyroxine-binding proteins by phenytoin, and the interaction between medications, like amiodarone which increases the effect of Digoxin which, in turn, raising your serum concentration. The in vitro effects are manifested in interference of medicine with the method of analysis, as for example, ascorbic acid which in large quantity reduces the level of glucose in serum glucose oxidase method.(7,8)

Even with analysis technologies that have changed over the decades, it is still susceptible to interference by medicines for both enzymatic and immunological methods methods. With the knowledge of these interferences, new methods and apparatus to quantify or identify substance, are entered into the world market. These means of analysis are previously tested and have manuals that indicate the type of medicine interference. These tests follow a study that has a selection of medicine through eligibility criteria. They include in such judicious, items such as: high serum concentration of medicine, knowledge of interference in the method, the frequency of use of the medicine, the in vivo relevance, recent documentation.(9)

It is important to note that a medication may interfere with the determination of an analyte specifically for a methodology, without interfering the results of tests for the same analyte accomplished through other methods. As an example, the dosage of glucose in the urine, when performed by enzymatic methods, have their values reduced by Ascorbic acid and levodopa. However, if you used method with Benetict solution, glucose levels can be increased with the use of Ascorbic acid, chloral hydrate and cefalosporima.(1)







There are many drugs that interfere in laboratory tests, both in vitro as in vivo, being the latest also called adverse reactions to medicines. An example of analytical interference is the false increase of the values of fructosamine in serum for patients using the captopril. As an example of interference by physiological effect can cite the enalapril and hydrochlorothiazide that cause changes in dosages of uric acid in serum. Other interference by physiological effect is observed in the use of propranolol and/or levothyroxine on examination of thyroxine (T4) free serum.(11)

It should be emphasized also that several classes of medications, besides the possibility of causing dyscrasias, can interfere with laboratory tests and, consequently, the clinical diagnosis. Hematologic changes induced by drugs can be avoided through measures such as monitoring of medicines, consisting of a pharmacovigilance practice that can be optimized through the mutual cooperation of different health professionals, always seeking the welfare of the patients.(12) Table 02 presents examples of hematologic changes that some medications can cause.

Studies show that the antihypertensive drug class represents complications for the profile lipid. The use continuous of diureticos thiazide (e.g.hydrochlorothiazide and chlorthalidone) raises the levels of total cholesterol (TC), the lipoproteina of low density (LDL) and lipoproteins of very low density (VLDL-C). However, the levels of lipoproteins of high density (HDL) does not suffer changes. The patients with hipertension and diabetes type 2 that make use of these medicaments are at risk before their interference in lipid metabolism.(13)




It is vital that drug interventions in laboratory tests are evaluated through clinical studies that have purpose to quantify the impact of variations in patient care and laboratory professionals know the limitations of the methodologies employed and the appropriate instructions.




Good practices in clinical and toxicological analysis are important to identify, reduce and/or eliminate the sources of potential errors in laboratory diagnosis. This will require continuing education of working professionals in clinical and toxicological analysis. One must be careful with the use of vitamins by the patient, since many of them may interfere with laboratory tests, such as Ascorbic acid which can cause false-negative results for determination of glucose, cholesterol, triglycerides and uric acid.

It is observed that many variables can interfere with the performance of the analytical phase and, consequently, the accuracy and precision of the results of the examinations, vital to medical conduct and, ultimately, for the well-being of the patient.

With that stresses the importance of enhancing the knowledge of professionals to be transmitted the required information to the population and to reduce the occurrence of these interferences.




Objetivo: Obter conhecimento científico sobre o uso de drogas que causam interferência nos resultados de testes laboratoriais. Trata-se de uma revisão integrativa da literatura que utilizou bancos de dados da Lilacs, da SciELO e Medline, e, para a busca de artigos, foram selecionadas as palavras-chave em Português e Inglês utilizando-se os testes da Bireme (DeCS): testes interações laboratoriais, interações medicamentosas e interferências. A pesquisa publicada em Inglês, Português ou Espanhol foi publicada sob a forma de artigos, resenhas, dissertações e teses publicadas entre 2009 e 2016. A interferência causada pela medicação é um grande problema porque o paciente pode estar usando várias drogas prescritas e automedicação. Entre os medicamentos mais utilizados, o paracetamol provoca um aumento da fosfatase alcalina e bilirrubina, bem como alguns corticosteroides, como a hidrocortisona, que eleva o cloro devido à retenção de sal e água. Nos exames hematológicos, a redução dos eritrócitos pode ser provocada pelo uso de aciclovir, amitripilina, captopril, cimetidina ou levodopa. Enfatiza-se a importância de uma avaliação clínica efetiva do paciente, de forma que o uso de medicamentos seja observado e, assim, seja possível garantir a qualidade nos resultados dos testes laboratoriais.



Laboratório; Teste de laboratório; Medicamento



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Sandna Larissa Freitas dos Santos

Av. Placido Castelo, 1909, Central

Quixadá-CE, Brasil