Background Improvement of preventive services for adults can be achieved by opportunistic or organised methods in primary care. The unexploited opportunities of these approaches were estimated by our investigation. Methods Data from the Hungarian implementation of European Health Interview Surveys in 2009 (N = 4709) and 2014 (N = 5352) were analysed. Proportion of subjects used interventions in target group (screening for hypertension and diabetes mellitus, and influenza vaccination) within a year were calculated. Taking into consideration recommendations for the frequency of intervention, numbers of missed interventions among patients visited a general practitioner in a year and among patients did not visit a general practitioner in a year were calculated in order to describe missed opportunities that could be utilised by opportunistic or organised approaches. Numbers of missed interventions were estimated for the entire population of the country and for an average-sized general medical practice. Results Implementation ratio were 66.8% for blood pressure measurement among subjects above 40 years and free of diagnosed hypertension; 63.5% for checking blood glucose among adults above 45 and overweighed and free of diagnosed diabetes mellitus; and 19.1% for vaccination against seasonal influenza. There were 4.1 million interventions implemented a year in Hungary, most of the (3.8 million) among adults visited general practitioner in a year. The number of missed interventions was 4.5 million a year; mostly (3.4 million) among persons visited general practitioner in a year. For Hungary, the opportunistic and organised missed opportunities were estimated to be 561,098, and 1,150,321 for hypertension screening; 363,270, and 227,543 for diabetes mellitus screening; 2,784,072, and 380,033 for influenza vaccination among the < 60 years old high risk subjects, and 3,029,700 and 494,150 for influenza vaccination among more than 60 years old adults, respectively. By implementing all missed services, the workload in an average-sized general medical practice would be increased by 12-13 opportunistic and 4-5 organised interventions a week. Conclusions The studied interventions are much less used than recommended. The opportunistic missed opportunities is prevailing for influenza vaccination, and the organised one is for hypertension screening. The two approaches have similar significance for diabetes mellitus screening.
