[Impact of the implementation of ICD-10 2016 version and Iris software on mortality statistics in Italy]

to assess the impact of coding causes of death with the ICD-10 2016 version and the software Iris on Italian official statistics on mortality.

coding of a sample of death certificates with two different coding systems (bridge coding).

a sample of 63,525 deaths occurred throughout 2015 among people aged over one year, already coded using the ICD-10 2009 version and the Mortality Medical Data System (MMDS) software, was re-coded through the ICD-10 2016 version and the Iris software.

the transition matrix between the two coding systems was realized and the agreement percentages between the two coding systems, the comparability ratios, and the relative 95% confidence intervals were calculated. Comparability ratios have been calculated for both the underlying cause of death and the multiple causes.

overall, 79% of deaths showed exactly the same underlying cause of death (ICD-10 code, 4 digits) in the two coding systems. On the three-digit level, the agreement was 89%; on ICD-10 chapter level, the agreement was 95%. At the chapter level, the most important changes were observed for: • certain infectious and parasitic diseases (-18% in ICD-10 2016/Iris); • diseases of the genitourinary system (-17%); • diseases of the respiratory system (+7%); • diseases of the nervous system and sense organs (+5%); • external causes of morbidity and mortality (+5%). Analyzing the multiple causes, the most important changes were observed for: • certain infectious and parasitic diseases (-19% in ICD-10 2016/Iris); • external causes of morbidity and mortality (+28%); • symptoms, signs, and abnormal clinical and laboratory findings, not elsewhere classified (+7%).

the results are very useful to explain any change in the Italian statistics on mortality comparing 2015 with the following years.