[Estimation of the underreporting of malaria measurement in ten municipalities of the Pacific coast of Nariño during 2009]

[[[ Introduction: ]]] The complete and effective collection of data of malaria cases is essential to formulate operative plans, as well as to develop and apply policies for its prevention and control. However, in Colombia, not all of the identified cases are notified nor incorporated into the surveillance system. This underreport represents a serious problem for decision makers. [[[ Objective: ]]] To estimate the type and quantity of errors made during the completion of the malaria individual case reporting form and its digitization level, through the use and monitoring of the reporting form in ten municipalities of Nariño in 2009. [[[ Materials and methods: ]]] A descriptive cross-sectional study with a non-probabilistic and convenience sample of diagnosis and treatment sites was carried out. Copies of the reporting forms from these sites and of the Public Health Surveillance System database were taken to compare them case-by-case. Proportions were calculated. [[[ Results: ]]] In more than 60% of the 2,816 reporting forms of positive cases the information about municipality of residence, municipality of origin and occupation was not reported. The case-by-case comparison revealed that 845 (30.0%) notification forms were not digitized at all. Information of variables such as residence, name of the municipality, and date of onset of symptoms were neither complete nor exact in more than 50% of the cases. [[[ Conclusions: ]]] The use of copies of the reporting forms allows knowing the underreporting due to lack of digitization. One third of the cases can be recovered.