Implementation of a text messaging intervention to patients on warfarin therapy in Brazilian primary care units: a quasi-experimental study

BMC Prim Care. 2022 Mar 23;23(1):54. doi: 10.1186/s12875-022-01647-5.


Background: Warfarin remains the most affordable oral anticoagulant in many countries. However, it may have serious side effects, and the success of the therapy depends on the patient's understanding of the medication and their adherence to treatment. The use of short messages services (SMS) is a strategy that can be used to educate patients, but there are no studies evaluating this intervention in patients taking warfarin. Therefore, we aimed to develop, implement, and assess the feasibility of an intervention using SMS to primary care patients taking warfarin in a medium-sized Brazilian city.

Methods: A bank of 79 SMS was drafted and validated by an expert panel. During 6 months, three times a week, patients received messages about anticoagulation with warfarin. At baseline and after 3 months, we assessed their knowledge and adherence with validated instruments. At the end of the follow-up, participants answered a satisfaction questionnaire. Subsequently, a scale-up phase was conducted, with another round of the intervention including 82 participants (29 from the first phase and 53 newly recruited). Seven months after the end of the scale-up, we asked the patients for their insights about the long-term effects of this program. All patients signed informed consent. The study was approved by the Research and Ethics committee of the Universidade Federal de Minas Gerais.

Results: In the pilot, 33 (89.2%) patients completed the follow-up. Among the participants who answered the satisfaction questionnaire (n = 29), 86.2% considered that the intervention motivated a healthy lifestyle and improved their understanding of warfarin therapy. All patients were willing to continue receiving the messages. Adherence measured by the Measure of Adherence to Treatment (MAT) test was high in the pre-intervention assessment and remained high (96.7% vs. 93.3%; p = 1.0000). The proportion of patients who achieved > 75% correct answers on the Oral Anticoagulation Knowledge (OAK) test increased from 6.5% to 25.6, p = 0.0703. In the scale-up, 23 patients answered the long-term assessment questionnaire. The main long-term knowledge reported was dietary information. Nine patients received the messages but did not remember their content.

Conclusion: The intervention was well-accepted and had a positive impact on patient's knowledge about oral anticoagulation therapy. The scale-up assessment reinforced the need to constantly monitor digital interventions.

Keywords: Anticoagulant; Cardiovascular disease; Digital health; E-health; M-health; SMS; Text-messages; Warfarin.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anticoagulants / therapeutic use
  • Brazil
  • Humans
  • Primary Health Care
  • Text Messaging*
  • Warfarin* / therapeutic use


  • Anticoagulants
  • Warfarin