How to Minimize ‘Lost to Follow-up’ in a Cohort Study in Pharmacoepidemiology? :
10.3820/jjpe.12.1
- VernacularTitle:薬剤疫学のコホート研究における追跡不能を最小化する方法の検討
- Author:
Eri KAWABE
;
Kazuo SAMIZO
;
Tsugumichi SATO
;
Kiyoshi KUBOTA
- Publication Type:Journal Article
- Keywords:
Prescription-Event Monitoring;
J-PEM;
Cohort study;
follow-up;
lost to follow-up
- From:Japanese Journal of Pharmacoepidemiology
2007;12(1):1-12
- CountryJapan
- Language:Japanese
-
Abstract:
Objective : To find methods to minimize ‘lost to follow-up’ in the long-term follow-up in a pilot study of Prescription-Event Monitoring in Japan (J-PEM) where hypertensive subjects who took losartan or a control drug and gave informed consent to the study were directly followed by researcher for years.
Design : Cohort Study
Methods : We conducted the follow-up survey twice, in which questionnaires were sent to hypertensive patients who had consented to being involved in the survey and returned it by mail. In the questionnaire, we asked about the use of the monitoring drug, change of medical institutions for the treatment of hypertension, significant health-related events. In the second survey, we reminded the non-responders by a letter of reminder and by telephone. When no information was obtained from the subject, we sent a letter, together with a copy of the informed consent given by the subject, to the municipal office where the subject's home was registered to inquire about the subject's current address and related information including the vital status. We calculated Standardized Mortality Ratio (SMR) using the information on death obtained from the mailed questionnaires, telephone and information in the municipal office.
Results : In a pilot study of J-PEM on losartan, 4344 and 3517 questionnaires were sent to pharmacists and doctors, respectively. The doctors handed the informed consent form to the patients and 422 patients agreed to participate the study and sent back the signed form to the study office. In the first and second surveys, a questionnaire was mailed to the subject approximately 1 and 5 years after the first prescription of losartan or a control drug, respectively. The response rate was 73 and 60% in the 1 st and 2 nd survey, respectively. In the manuscript, the results of the 2 nd survey were mainly presented. The reminders by mail and telephone increased the response rate from 60 to 81% and provided the information on the vital status for 86% of the subjects. The response rate was further increased to 84% and the vital status was known for 99% when the information in the municipal office was used. SMR was estimated to be 0.59 (95% CI : 0.34-1.01) before reminding subjects, 0.78 (0.52-1.17) after reminding subjects by a letter and telephone and 0.92 (0.65-1.31) after further addition of the information from the municipal office. During the 5 years of the observation, 21% of 343 subjects who sent back a filled questionnaire did and 70% did not change the clinic/hospital where they received the care for hypertension, while 9% did not answer the relevant question.
Conclusion : The method of the systematic survey may be useful in minimizing the ‘lost to follow-up’ subjects in the long-term pharmacoepidemiology studies in Japan where a patient can change the clinic/hospital for his/her own health care without any letter of reference. In the systematic survey, the researchers may try to follow the subjects by using several methods including reminders like a letter or telephone as well as the use of the information in the municipal office. To facilitate better follow-up, a careful design of the study including the proper design of the informed consent form is essential to maximize the amount and quality of the available information, particularly when the subject has a serious event or dies in a hospital or institution apart from that where the patient has been registered.
