Serum neurofilament light chain in hereditary transthyretin amyloidosis: validation in real-life practice

Figures & data

Table 1. Baseline characteristics.

	All Pre-treatment*	T60A	V30M	Other^^		G47V	V112I	S77Y	A97S	N = 1 variants^#
n	58	25	11	22	p value	4	4	3	2	9
Age (Range; IQR)	62.2 (33.2–79.5; 55.2–70.2)	64.0 (42.6–79.5; 55.8 − 70.5)	62.2 (42.2–75.0; 50.1–66.7)	61.6 (33.2 − 78.4; 55.1–70.0)	0.75	55.9 (54.6–61.8; 55.5–57.4)	75.8 (69.5–78.4; 73.7–75.9)	69.5 (64.2–74.1; 67.2–72.1)	63.0 (61.4–64.7; 62.2–63.9)	54.8 (33.2–73.2; 51.0–60.7)
Gender M F	39 (67%) 19 (33%)	19 (76%) 6 (24%)	7 (64%) 4 (36%)	13 (59%) 9 (41%)	0.45^∼	3 (75%) 1 (35%)	2 (50%) 2 (5–%)	2 (67%) 1 (33%)	2 (100%) 0 (0%)	4 (44%) 5 (56%)
Creatinine	101.0 (20.9; 55)	84.6 (18.4; 22)	81.2 (20.7; 9)	88.6 (23.8)	0.63	103.5 (39.2)	97.3 (25.5)	77.0 (21.2)	71.0 (24.0)	85.9 (13.9)
eGFR	76.2 (16.3;55)	78.2 (13.0; 23)	72.3 (25.1;10)	76.1 (15.2)	0.65	68.3 (22.4)	68.0 (16.7)	85.0 (13.5)	84.5 (7.78)	78.3 (12.0)
PND (n)					0.89^∼
0	19	7	6	6		1	1	–	2	2
1	17	8	2	7		1	1	1	–	4
2	11	4	2	5		1	–	2	–	2
3A	8	5	–	3		1	1	–	–	1
3B	3	1	1	1		–	1	–	–	–
FAP (n)					0.50^∼
0	15	6	5	4		1	0	–	2	1
1	31	13	5	13		2	2	2	–	7
2	12	6	1	5		1	2	1	–	1
NIS	8 (0–25.9; 52)	10 (2–20.3; 24)	1 (0–4.5; 10)	18.0 (1.5–28.5; 18)	0.10	27 (13.5–28.5; 3)	16.0 (11.0–18.0; 3)	29.3 (22.1–36.4; 2)	0.0 (0.0–0.0)	26.5 (6.0–29.5; 8)
NIS-LL	8 (0–19; 53)	8 (2–17.25; 24)	1 (0–4.5; 10)	14.0 (3.0–22.7; 19)	0.15	17.0 (8.5–21.5; 3)	14.0 (10–14; 3)	23.3 (18.1–28.4; 2)	0.0 (0.0–0.0)	17.0 (8.0–23.5)
MRC	70 (68–70; 55)	70 (68–70; 24)	70 (70–70)	68.5 (66–70; 20)	0.06	68.0 (67.5–69.0; 3)	69.5 (65–70)	66.5 (65.8–67.3; 2)	70 (70–70)	68.0 (66.0–70.0)
CMTSS	1 (0–5.75; 36)	1 (0–5.5; 15)	0.5 (0.0–4.5; 8)	1.0 (0.0–5.0; 13)	0.94	3.0 (1.5–4.5; 2)	2.0 (1.0–3.0; 2)	5.0 (5.0–5.0; 2)	0 (0.0–0.0)	1.0 (0.0–6.0; 5)
CMTES	5 (2.0–12.0; 35)	5.5 (2.3–12.8; 14)	2.5 (0.8–9.5; 8)	5.0 (3.0–12.0; 13)	0.21	7.5 (3.8–11.3; 2)	5.5 (4.3–6.8; 2)	11.5 (11.3–11.8; 2)	3.0 (3.0–3.0)	5.0 (5.0–12.0; 5)
CMTNS	5 (0.3–14.0; 29)	5.5 (0.5–12.5, 10)	2 (0.5–11.5; 8)	9.0 (4.0–15.5; 11)	0.79	9.5 (4.8–14.3; 2)	6.5 (5.3–7.8; 2)	17 (17.0–17.0; 1)	4 (4.0–4.0; 1)	9.0 (5.0–14.0; 5)
NfL (pg/ml)	92.5 (29.9–163)	104 (32.0–154)	64.3 (12.5–109)	105 (59.6–194)	0.18	218 (151–245)	78.5 (43.8–78.5)	70.2 (67.2–72.1)	157.9 (129–187)	105 (72.8–155)

TTR gene variants are reported according to the ISA amyloid nomenclature recommendations 2022 [43]. Normally distributed variables are reported as mean (± standard deviation; n, if n differs from the total number in the cohort). Differences in means between groups are evaluated by ANOVA and post-hoc Student’s t-test. Non-normally distributed variables are reported as median (IQR25%-75%; n, if n differs from the total number in the cohort) with differences in medians between groups evaluated by Kruskal-Wallis and post hoc Mann-Whitney U tests. ^∼ Differences in gender, PND and FAP across the groups were evaluated by the Chi-squared statistic. Significance level defined as p < 0.05.

* Indicates cohort used for cross-sectional pre-treatment analyses.

^{^} Indicates “Other” group cohort used for mutation analysis comprising of G47V, V112I, S77Y, A97S, S23N, E42D, H90D, A120S, E54G, R34G, E89K, I107V and F33I.

^# n = 1 variants include 1 individual each of ATTRv mutations: S23N, E42D, H90D, A120S, E54G, R34G, E89K, I107V and F33I.

Abbreviations: Peripheral neuropathy disability score (PND), Familial Amyloid Polyneuropathy stage (FAP), Neuropathy impairment score (NIS), Neuropathy impairment score lower limb subset (NIS-LL), Medical Research Council score (MRC); Rasch-modified Charcot-Marie-Tooth Neuropathy score version 2, symptom score (CMTSS), symptom and examination score (CMTES), and total score (CMTNS), Norfolk Quality of life – Diabetic Neuropathy score (Norfolk QOL-DN).

Figure 1. Correlations between logged neurofilament light chain concentrations (log(NfL), pg/ml) and examination scores (A-F). A: Neuropathy impairment score (NIS), B: Neuropathy impairment score, lower limb subset (NIS-LL), C: Rasch-modified Charcot-Marie-Tooth symptom score CMTSS), D: Rasch-modified Charcot-Marie-Tooth symptom and examination score (CMTES), E: Rasch-modified Charcot-Marie-Tooth neuropathy composite score (CMTNS) and F: Medical Research Council score (MRC).

Figure 2. Serum neurofilament light chain (NfL) increases with disease severity (A-B) and with transition to symptomatic disease (C-D). A-B: Baseline logged neurofilament light chain (log(NfL), pg/ml) increases with increasing peripheral neuropathy disability (PND) scores (A) and familial amyloid polyneuropathy (FAP) stage (B). Black circles indicate raw data values. C-D: Longitudinal evaluation of logged neurofilament light chain (log(NfL), pg/ml) levels according to clinical group as assessed by generalised linear mixed model. C: Differences in log(NfL) over time can be distinguished by group status demonstrating significant increases in symptomatic and sensorimotor converters irrespective of time, when compared to asymptomatic and sensory converting patients, D: Longitudinal changes (years) in log(NfL) according to group status, where A: Asymptomatic (yellow), SC: Sensory converters (red), MC: Sensorimotor converters (aqua) and S: Symptomatic (green) groups.

Individuals were characterised as asymptomatic (A) if they remained asymptomatic throughout the follow-up period with PND 0, MRC 70 and NIS 0. Symptomatic individuals (S) had evidence of a symptomatic neuropathy at baseline and throughout the follow-up period, with NIS > 5 or MRC score < 70 and PND score of 1 or above at baseline. An individual was categorised as a sensory converter (SC), if they were asymptomatic at initial review and during follow-up they transitioned from PND or FAP scores of 0 to 1, NIS 0 to > 0 and maintained an MRC score of 70. Sensorimotor converters (MC) were individuals who were asymptomatic at baseline and converted from a PND score of 0 or 1 to a score of ≥ 2 and developed muscle weakness (MRC score < 70).

Table 2. Baseline characteristics of longitudinal groups.

	Asymptomatic (A)	Sensory converters (SC)	Sensorimotor Converters (MC)	Symptomatic (S)
n	11	11	5	16	p-value	A vs SC	A vs MC	A vs S	SC vs MC	SC vs S	MC vs S
Age (Range; IQR)	56.19 (42.2–76.5; 50.6–67.1)	61.38 (49.96–76.59; 55.57–65.13)	58.45 (53.17–64.80; 55.16–64.67)	65.95 (42.64–79.47; 60.31–43.67)	.31	NS	NS	NS	NS	NS	NS
Gender M / F	7 / 4	7 / 4	3 / 2	10 / 6	1^#
ATTR Variant	T60A − 5	T60A − 6	T60A − 2	T60A − 7	N/A
	V30M − 4	V30M − 2	V30M- 2	G47V − 2
	A120S/V122I − 1	A97S/G47V/ S23N − 1	A97S − 1	V30M/I107V/ R34G/E54G/ S77Y/E42D/ V122I − 1
Creatinine	85 (21.16)	87 (19.15)^ 164 (172.35)*	82 (11.48)	85 (22.51)	.98^	NS	NS	NS	NS	NS	NS
eGFR	78 (15.28)	71 (10.61)^ 67 (21.56)*	79 (10.06)	80 (14.40)	.45	NS	NS	NS	NS	NS	NS
PND (n)					N/A
0	11	11	5	–
1	–	–	–	4
2	–	–	–	4
3A	–	–	–	8
3B	–	–	–	–
FAP (n)					N/A
0	11	11	5	–
1	–	–	–	8
2	–	–	–	8
NIS	0 (0–1.5)	0 (0–1.5)	0 (0–4; 3)	28.88 (19.25–30.00; 14)	<.0001	0.80	1	<0.0001	0.84	<0.0001	0.01
NIS-LL	0 (0–1.5)	0 (0–1.5)	0 (0–3; 3)	16.50 (14.25–23.5; 14)	<.0001	0.74	1	<0.0001	0.76	<0.0001	0.01
MRC	70 (70–70)	70 (70–70)	70 (70–70; 4)	68 (66–68.75; 14)	<.0001	NA	NA	0.0001	NA	0.0001	0.01
CMTSS	0 (0–0; 10)	0 (0–0; 6)	0 (0–0; 2)	6.00 (4.5–6.0; 7)	.0003	0.87	0.62	<0.001	0.77	0.002	0.05
CMTES	2 (0–3; 10)	1.5 (0–3; 5)	4 (3.5–4.5; 2)	12.00 (8.5–12.5; 7)	.001	0.79	0.15	<0.001	0.22	0.005	0.06
CMTNS	2 (0–3; 7)	0 (0–4; 5)	5 (5–5; 1)	11.5 (9–14;6)	.005	1	0.26	0.003	0.53	0.007	0.20
NfL (pg/ml)	14.3 (11.3–65)	36.0 (18.9–76.1)	106 (104–136)	134 (114–259)	<.0001	0.08	0.002	<0.0001	0.07	0.0001	0.24
NfLx increase	1	2.5	7.4	9.3	N/A

Normally distributed variables are reported as mean (± standard deviation; n, if n differs from the total number in the cohort). Differences in means between groups are evaluated by ANOVA. Non-normally distributed variables are reported as median (IQR25%–75%; n, if n differs from the total number in the cohort) with differences in medians between groups evaluated by Kruskal-Wallis.

^# Differences in gender across the groups were evaluated by the Chi-squared statistic. Significance level defined as p < 0.05.

* Including outliers.

^{^} without outliers.

Abbreviations: Peripheral neuropathy disability sc (PND), Familial Amyloid Polyneuropathy stage (FAP), Neuropathy impairment score (NIS), Neuropathy impairment score lower limb subset (NIS-LL), Medical Research Council score (MRC); Rasch-modified Charcot-Marie-Tooth Neuropathy score version 2, symptom score (CMTSS), symptom and examination score (CMTES), and total score (CMTNS), Norfolk Quality of life – Diabetic Neuropathy score (Norfolk QOL-DN).

Table 3. NfL cut-off values: sensitivity and specificity.

Groups	NfL cut-off	AUC	95% CI	Sensitivity	Specificity
Absolute NfL cut-off values
PND 0 and 1 vs PND > 2	52.2	0.83	0.71–0.95	100	55.5
A and SC vs MC and S	64.5	0.87	0.81–0.94	91.9	78.7
A vs MC and S	64.5	0.95	0.90–0.99	92.0	88.5
A vs SC, MC and S	88.9	0.84	0.77–0.91	62.9	96.2
Relative NfL cut-off values
A vs SC and MC	1.17 x	0.89	0.71–1.00	88.9	80.0

Abbreviations: Polyneuropathy disability score (PND), A: asymptomatic, SC: sensory converters, S: Symptomatic and MC: Sensorimotor converter cohorts. Individuals were characterised as asymptomatic (A) if they remained asymptomatic throughout the follow-up period with PND 0, MRC 70 and NIS 0. Symptomatic individuals (S) had evidence of a symptomatic neuropathy at baseline and throughout the follow-up period, with NIS > 5 or MRC score < 70 and PND score of 1 or above at baseline. An individual was categorised as a sensory converter (SC), if they were asymptomatic at initial review and during follow-up they transitioned from PND or FAP scores of 0 to 1, NIS 0 to > 0 and maintained an MRC score of 70. Sensorimotor converters (MC) were individuals who were asymptomatic at baseline and converted from a PND score of 0 or 1 to a score of ≥ 2 and developed muscle weakness (MRC score < 70).

Figure 3. Post-treatment alterations in neurofilament light chain (NfL). A: Change in NfL correlates with change in transthyretin (TTR). Change in NfL and TTR are both calculated as recent post-treatment concentration divided by baseline pre-treatment concentration; B: Greater reduction in NfL (<1: reduction, >1: increase) is found with increasing TTR suppression (%). C: Longitudinal evaluation (years) of logged neurofilament light chain (log(NfL), pg/ml) concentration after effective treatment (>50% TTR suppression) as assessed by generalised linear mixed model. Black circles indicate raw data values.

Buxbaum JN, Dispenzieri A, Eisenberg DS, et al. Amyloid nomenclature 2022: update, novel proteins, and recommendations by the international society of amyloidosis (ISA) nomenclature committee. Amyloid. 2022;29(4):213–219. doi:10.1080/13506129.2022.2147636.

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