Estimating clinical stage of amyotrophic lateral sclerosis from the ALS Functional Rating Scale.
Balendra R., Jones A., Jivraj N., Knights C., Ellis CM., Burman R., Turner MR., Leigh PN., Shaw CE., Al-Chalabi A.
ALS is a progressive neurodegenerative disease. The stage of disease reached can be described using a simple system based on the number of central nervous system regions involved. Historically, datasets have not attempted to record clinical stage, but being able to re-analyse the data by stage would have several advantages. We therefore explored the possibility of using an algorithm based on the revised ALS Functional Rating Scale (ALSFRS-R), which is commonly used in clinical practice, to estimate clinical stage. We devised an algorithm to convert ALSFRS-R score into clinical stage. ALSFRS-R domains were mapped to equivalent CNS regions. Stage 4 is reached when gastrostomy or non- invasive ventilation is needed, but as a proxy we used provision. We collected ALSFRS-R from clinic visits, and compared the estimation of clinical stage from the ALSFRS-R with the actual stage. Results showed that the agreement between staging by the two methods was excellent with an intraclass correlation coefficient of 0.92 (95% confidence interval 0.88-0.94). There was no systematic bias towards over-staging or under-staging using the algorithm. In conclusion, we have shown that clinical stage in ALS can be reliably estimated using the ALSFRS-R in historical data and in current data where stage has not been recorded.