A unidirectional mapping of ICD-8 to ICD-10 codes, for harmonized longitudinal analysis of diseases

Periodic revisions of the international classification of diseases (ICD) ensure that the classification reflects new practices and knowledge; however, this complicates retrospective research as diagnoses are coded in different versions. For longitudinal disease trajectory studies, a crosswalk is an essential tool and a comprehensive mapping between ICD-8 and ICD-10 has until now been lacking. In this study, we map all ICD-8 morbidity codes to ICD-10 in the expanded Danish ICD version. We mapped ICD-8 codes to ICD-10, using a many-to-one system inspired by general equivalence mappings such that each ICD-8 code maps to a single ICD-10 code. Each ICD-8 code was manually and unidirectionally mapped to a single ICD-10 code based on medical setting and context. Each match was assigned a score (1 of 4 levels) reflecting the quality of the match and, if applicable, a "flag" signalling choices made in the mapping. We provide the first complete mapping of the 8596 ICD-8 morbidity codes to ICD-10 codes. All Danish ICD-8 codes representing diseases were mapped and 5106 (59.4%) achieved the highest consistency score. Only 334 (3.9%) of the ICD-8 codes received the lowest mapping consistency score. The mapping provides a scaffold for translation of ICD-8 to ICD-10, which enable longitudinal disease studies back to and 1969 in Denmark and to 1965 internationally with further adaption.

Equating Mini-Mental State Examination (MMSE) and Montreal Cognitive Assessment (MoCA) scores: conversion norms from a healthy Italian population sample

BACKGROUND

This study aimed to provide equating norms for the Mini-Mental State Examination (MMSE) and Montreal Cognitive Assessment (MoCA) from a sample of healthy Italian adults.

METHODS

Four-hundred and seven Italian healthy adults (165 males, 242 females; mean age = 60.61 ± 13.74 years, range= 20-93; mean education = 12.2 ± 4.42 years, range= 4-25) were administered the MMSE and the MoCA. 'MMSE-to-MoCA' and 'MoCA-to-MMSE' conversion tables were derived via log-linear smoothing equi-percentile equating (LSEE). Equivalence between empirical and conversion-derived scores was determined with a two one-sided test (TOST) procedure.

RESULTS

Conversion-derived scores were statistically equivalent to empirical ones for both the MMSE (p = 0.948) and the MoCA (p = 0.437). The LSEE yielded impossible/unreliable conversion estimates for floor scores on both tests, whereas conversions for uppermost scores were highly consistent.

DISCUSSION

The present data will help avoid inter-rater heterogeneity in cross-sectionally and longitudinally adopting either one of the two cognitive screening tests, and to retrospective analyze data collected via either one test or the other.