Serum anti-PAD4 autoantibodies are present in cystic fibrosis children and increase with age and lung disease severity

Figures & data

Table 1. Demographic and clinical characteristics of CF patients.

	N = 104
Demographic Characteristics
Sex-Male, N (%)	65 (62.5%)
Age at collection, years, mean ± SD	23.9 ± 13.5
Race, N (%)
Caucasian	96 (92.3%)
Black	7 (6.7%)
Asian	1 (1%)
Hispanic ethnicity	1 (1%)
Clinical Characteristics
ppFEV1 at collection, Median (25^th, 75^th) (N = 99)	84.6 (64.8, 95.8)
Baseline ppFEV1, Median (25^th, 75^th) (N = 99)	85.4 (67.2, 95.7)
CFTR genotype
Homozygous F508del	46 (44.2%)
Heterozygous F508del	38 (36.5%)
Other	20 (19.2%)
Sweat chloride^a, mmol/L, mean ± SD (N = 77)	97.7 ± 21.4
Pancreatic enzyme use at collection (N = 103)	96 (93.2%)
CFTR modulator use at collection	22 (21.2%)
BMI percentile^b, mean ± SD (N = 41)	54.5 ± 29.0
BMI^c, mean ± SD (N = 60)	24.3 ± 4.8
Number of pulmonary exacerbations requiring IV antibiotics in the 2 years prior to sample collection, Median (25^th, 75^th)	1 (0, 2)
Glucose status^d (N = 79)
CF-related diabetes	22 (27.8%)
Impaired glucose tolerance	10 (12.7%)
Normal glucose tolerance	47 (59.5%)
Respiratory microbiology at sample collection, N (%)
Staphylococcus aureus	47 (45.2%)
MSSA	34 (72.3%)
MRSA	13 (27.7%)
Pseudomonas aeruginosa	34 (32.7%)
Non-mucoid	10 (29.4%)
Mucoid	24 (70.6%)
Chronic Pseudomonas aeruginosa^e, N (%)	41 (39.4%)

Abbreviations: BMI: body mass index; ppFEV₁: forced expiratory volume in 1 s percent predicted; IV: intravenous; MSSA: methicillin-sensitive staphylococcus aureus; MRSA: methicillin-resistant staphylococcus aureus.

^aAverage of the subject’s two sweat chloride sites.

^bFor subjects 2–19 years of age.

^cFor subjects ≥20 years of age.

^dNormal glucose tolerance: 2 h glucose < 140 mg/dL; impaired glucose tolerance: 2 h glucose values 141–199 mg/dL; CF related diabetes: 2 h glucose > 200 mg/dL.

^e2 or more cultures in the 12 months prior to sample collection with 50% or greater being positive for Pseudomonas aeruginosa.

Figure 1. Anti-PAD4 autoantibodies are elevated in CF children (a) and adults (b) compared to healthy controls.

Figure 2. Serum anti-PAD4 autoantibody levels in CF patients correlate with (a) age and (b) ppFEV1 (Pearson correlation coefficient).

Table 2. Univariate analysis of continuous CF clinical co-variates and anti-PAD4 autoantibodies.

	Anti-PAD4 autoantibodies (log10 U/ml)
Characteristic	N	Pearson CC	P-value
Age	104	0.584	<.001
Sweat chloride (mmol/L)^a	77	0.054	.642
ppFEV1 at collection	99	−0.481	<.001
Baseline ppFEV1	99	−0.475	<.001
BMI%ile^b	41	−0.099	.539
BMI^c	60	−0.129	.324
Number of pulmonary exacerbations requiring IV antibiotics in past 2 years	104	0.093	.347
log dsDNA IgA autoantibodies (U/ml)	104	0.259	.008
Absolute neutrophil count^d	55	0.060	.664

Abbreviations: BMI: body mass index; IV: intravenous; ppFEV₁: forced expiratory volume in 1 s percent predicted.

^aAverage of the subject’s two sweat chloride sites.

^bFor subjects 2–19 years of age.

^c For subjects ≥20 years of age.

^dSerum absolute neutrophil count collected within 6 months prior to PAD4 autoantibody level, during a period of clinical stability.

Table 3. Univariate analysis of categorical CF clinical co-variates and anti-PAD4 autoantibodies.

		Anti-PAD4 autoantibodies (U/ml)
Characteristic	Category	N	Median	IQR (25%,75%)	Kruskal–Wallis P-value
Sex	Male	65	69,105	37,595, 113,167	.068
	Female	39	88,607	48,932, 153,691
Race	White	96	72,178	40,571, 124,391	.152
	Black	7	130,336	75,214, 218,500
	Asian	1	118,762	---
CFTR genotype	Homozygous	46	59,815	37,595, 113,303	.440
	Heterozygous	38	85,720	47,736, 133,905
	Other	20	76,143	38,246, 133,918
Pancreatic Enzymes use	Yes	96	75,419	40,571, 136,821	.979
	No	7	69,105	48,932, 107,090
CFTR Modulator use	No	82	76,768	42,179, 139,738	.348
	Yes	22	63,631	40,512, 92,571
Underweight^a	No	94	76,208	42,179, 139,738	.370
	Yes	7	76,702	16,941, 100,500
Any pulmonary exacerbations requiring IV antibiotics in past 2 years	0	48	58,994	33,252, 123,107	.118
	> =1	56	81,997	48,333, 143,000
Glucose Status	Normal	47	76,833	47,428, 133,905	.099
	Impaired	10	38,615	24,917, 172,500
	CFRD	22	100,149	66,500, 180,775
Respiratory Microbiology
Pa-positive respiratory culture	No	70	59,815	36,464, 97,140	.001
	Yes	34	113,235	66,500, 179,000
Chronic Pa^b	No	63	54,798	33,432, 106,802	<.001
	Yes	41	100,628	66,500, 168,048
Mucoid Pa-positive respiratory culture	No	10	91,818	37,595, 148,500	.257
	Yes	24	117,319	71,205, 179,887
Staphylococcus aureus-positive respiratory culture	No	57	76,702	40,631, 148,500	.683
	Yes	47	69,105	42,179, 121,210
Staphylococcus aureus subtype	MSSA	34	67,000	42,179, 118,762	.887
	MRSA	13	69,105	43,798, 121,210
Co-infection with MRSA and Pa	No	97	75,254	42,095, 133,905	.654
	Yes	7	100,500	47,736, 121,210

Abbreviations: IV: intravenous; MSSA: methicillin-sensitive staphylococcus aureus; MRSA: methicillin-resistant staphylococcus aureus; Pa: Pseudomonas aeruginosa.

^aUnderweight if BMI%ile is <10^th %ile for ages 2-19 years or BMI <18.5 for ages ≥20 years.

^b2 or more cultures in the 12 months prior to sample collection with 50% or greater being positive for Pseudomonas aeruginosa.

Table 4. Multivariable linear regression model for CF clinical co-variates and log-PAD4 autoantibodies*.

		Anti-PAD4 autoantibodies (log10 U/ml)
Covariate	Level	B	95%CI Low	95%CI Up	P-value
ppFEV1		−0.004	−0.007	−0.001	.010
Age		0.013	0.007	0.018	<.001
Sex	Male	−0.055	−0.18	0.07	.382
	Female	–	–	–	–
Chronic Pa	No	−0.039	−0.18	0.10	.566
	Yes	–	–	–	–

*N = 99 subjects who had lung function data; five young paediatric subjects were developmentally unable to perform acceptably spirometry.