Maputo Central Hospital (MCH) is located in the city of Maputo (capital of Mozambique). Is a quaternary level hospital (the highest level in Mozambique) and is a national reference hospital. The direct catchment-population of the MCH is around 3 million inhabitants, and the indirect catchment-population is around 29 million inhabitants.
A cross-sectional hospital-based study was carried out in 2019, collecting secondary data (registered cases) from hospitalized patients with stroke from the years 2014–18, and first semester of 2019. All the Medicine wards (who admit stroke patients) from MCH were selected for the study data collection.
Building the endemic channel: Thresholds methods
Four threshold epidemic detection methods were used, namely: i) monthly mean for the past five years plus two times the standard deviation (mean + 2SD); ii) cumulative sum method (C-SUM), which is the mean calculated over the combined previous, current and following months’ data for the past five years; iii) C-SUM + 1.96SD; and iv) the 3rd quartile, which is the second highest value noted for the month over the past five years.
Description of the threshold methods
Mean + 2SD: uses the previous five years’ data to construct an admissions profile for an average year at that location. The alert threshold for each month is then determined as the mean plus two times the standard deviation.
C-SUM: is based on the construction of an average or base year by calculating the expected number of cases using the average for that month (and the previous and following month) during the past five years.
C-SUM + 1.96SD: is based on C-SUM method refined by adding a 95% confidence interval.
Third quartile: is based on the using of 3rd quartile for each month during the past five years. If the current month’s cases exceed quartile 3, an alarm is triggered—epidemic zone.
Outcomes of interest
The main outcomes are: (i) stroke cases and percentage per month per year (2014–18); (ii) monthly stroke threshold for the period 2014–18; (iii) stroke cases from January to June 2019.
Monthly stroke data from the period 2014–18 and January to June 2019 were collected from the Medicine wards registry books. These monthly data were introduced in a Microsoft® Office Excel® 2007 spreadsheet for organization, analysis and storage of data in tabular form. Monthly data from 2014–18 were used to calculate the percentage, mean and SD of registered stroke cases and to generate the epidemic thresholds. Data from January to June 2019 were used to analyze the 2019 trend over the thresholds. Graphics were generated to better illustrate the thresholds and for tracking first semester 2019.