Registration of Amyotrophic Lateral Sclerosis: Validity in the Danish National Patient Registry

Figures & data

Table 1 ALS Cohort Characteristics

Variable	Value
Total (N)	215
Age (Y), median	66 (IQR, 60–73)
Age (Y), range	34–92
Hospital of ALS diagnosis
Aarhus University Hospital	154 (71.6%)
Aalborg University Hospital	20 (9.3%)
Gødstrup Hospital	41 (19.1%)
CSF–data	126 (58.6%)
CSF cell count <10 per mm^3	126 (58.6%)
CSF NFL–data^a	27 (12.6%)
Increased CSF NFL (n=19) (ng/L), median	6774.5 (IQR, 4,558.5–10,000.0)
MRI of CNS–data	170 (79.1%)
Neurophysiological examination	187 (87.0%)
ALS defined be the revised El Escorial criteria^b
Clinically definite ALS	95 (44.2%)
Clinically probable ALS	85 (39.5%)
Clinically possible ALS	15 (7.0%)
ALS phenotype
Classic ALS	181 (84.2%)
Progressive bulbar palsy	≤10 (≤4.7%)
ALS with FTD	≤5 (≤2.3%)
Progressive muscle atrophy	20 (9.3%)
Genetically verified ALS	≤5 (≤2.3%)
First or second–degree relatives with ALS	5 (2.3%)
Riluzole treatment^c	157 (73.0%)

Notes: ^aNFL analysis was introduced in Denmark in 2018. ^bProgressive muscle atrophy (n=20) do not fulfill the revised El Escorial criteria, however, is included as an ALS variant. ^cRiluzole approved in Denmark from June 1996.

Abbreviations: ALS, amyotrophic lateral sclerosis; CNS, central Nervous system; CSF, cerebrospinal fluid; FTD, frontotemporal dementia; IQR, interquartile range; MRI, magnetic resonance imaging; N, number of cases; NFL, neurofilament light chain; PPV, positive predictive value; Y, years.

Table 2 Validity of ICD–Codes for Amyotrophic Lateral Sclerosis in the DNPR

Variable	Total (N)	ALS (N)	Non-ALS (N)	PPV (%)	95% CI
All	240	215	25	89.6	85.1–92.8
Males	139	124	15	89.2	83.0–93.4
Females	101	91	10	90.1	82.7–94.5
Year of diagnosis
1987–1999	52	47	5	90.4	79.4–95.8
2000–2009	83	75	8	90.4	82.1–95.0
2010–2022	105	93	12	88.6	81.1–93.3
Age at diagnosis (years)
<60	68	57	11	83.4	73.3–90.7
60–69	92	83	9	90.2	82.4–94.8
≥70	80	75	5	93.8	86.2–97.3

Abbreviations: ALS, Amyotrophic lateral sclerosis; CI, confidence interval; N, number of cases; PPV, positive predictive value.