As new versions of MedDRA and WHO Drug are released, companies are continually challenged to migrate, or "upversion," their data to the latest release. Many companies use the new version only for coding new data (leaving already coded data unchanged) or choose to re-code only those terms where the previous code is no longer available in the new version.
If you use either of these approaches, your versioning strategy falls short. Your versioning strategy must also determine if entries added to the new version are better choices for your previously coded data. Otherwise, like terms will be coded differently over time, impacting your analysis and reporting.