A revision to the United States national ALS registry’s algorithm to improve Case-Ascertainment

Figures & data

Figure 1 Original and proposed algorithms for defining cases in the National ALS Registry.

Table 1 Current and proposed classifications of individuals in the national ALS registry.

Registry-Eligible Cases^a	Current^b	Proposed^c
Yes	Definte ALS	Confirmed ALS^a
		Likely ALS^a
No	Possible ALS	Undetermined ALS
	Not ALS	Not ALS

^aOnly Registry-eligible cases will be added to the numerator in order to determine rates.

^bFor years 2011–2017.

^cFor years 2018 and forward.

Figure 2 Flow chart shows the filtering of Possible ALS individuals in current algorithm. ^aD1 definition: 1) an encounter coded for ALS (International Classification of Diseases, Ninth Revision ICD-10 G12.21) in 1 or more years in the same source, or 2) a death certificate listing ALS as a cause of death, or 3) a prescription for Riluzole.

Table 2 ALS patients with a Riluzole prescription in administration databases -- Current Algorithm.

	Possible ALS individuals
	2011		2012		2013		2014		2015		2016		2017
	n	%	n	%	n	%	n	%	n	%	n	%	n
Number of possible^a	720		558		311		16		1,079		964		411
Number converted to Confirmed case by 2017	305	42.4	213	38.2	96	30.9	6	37.5	395	36.6	215	22.3	N/A
Number converted to Confirmed case from D1^b definition by 2017	186	25.8	123	22.0	19	6.1	6	37.5	239	22.2	194	20.1	N/A
Number converted to Confirmed case with Riluzole and death certificate by 2017	131	18.2	67	12.0	5	1.6	0	–	91	8.4	77	8.0	N/A

^aPossible ALS individuals with only a Riluzole prescription.

^bD1 - ALS confirmed case if any two of the following: 1) an encounter coded for ALS (International Classification of Diseases, Ninth Revision ICD-10 G12.21) in 1 or more years in the same source, or 2)a death certificate listing ALS as a cause of death, or 3) a prescription for Riluzole.

Table 3 Number of ALS cases^a using the newly proposed algorithm and classification system for the National ALS Registry.

	Years
ALS Classification^b	2011	2012	2013	2014	2015	2016	2017
Confirmed	12,187	14,713	15,908	15,927	16,583	16,424	17,800
Likely^c	720	844	650	54	1,226	1,364	1,584
Total ALS cases	12,907	15,557	16,558	15,981	17,809	17,788	19,384

^aCumulative by year.

^bNew classifications: Confirmed and Likely ALS cases (i.e. Registry-eligible cases) equals "definite ALS" cases under existing classification.

^cLikely ALS cases are the newly added cases under the new algorithm.