First metatarsophalangeal joint synovial hypertrophy associated with vitamin D status in type 2 diabetes mellitus: An ultrasound-graded study

Table 1 Study population characteristics based on the degree of synovial hypertrophy, mean ± SD/n (%)

Variable	Total	Mild	Moderate-severe	P value
Number	98	40	58
Gender				0.896
Male	62 (63.3)	25 (62.5)	37 (63.8)
Female	36 (36.7)	15 (37.5)	21 (36.2)
Age (year), median IQR	56.0 (51.0-64.8)	58.5 (55.0-66.2)	55.0 (47.0-63.8)	0.0221
DD (year), median IQR	10.0 (4.0-15.0)	8.0 (4.0-15.0)	10.0 (3.2-16.5)	0.9421
UA (μmol/L), median IQR	314.5 (275.8-365.0)	314.5 (269.0-393.0)	314.5 (280.0-356.0)	0.3901
FPG (μg/dL), median IQR	6.9 (6.1-9.3)	6.9 (6.2-8.3)	6.5 (6.1-9.7)	0.9911
HbA1c (%), median IQR	8.2 (7.4-9.9)	8.0 (7.3-10.0)	8.2 (7.5-9.6)	0.8511
ALB (g/L)	41.3 ± 3.5	40.3 ± 3.2	42.0 ± 3.6	0.014
BMI (kg/m2), median IQR	24.1 (22.5-26.3)	24.1 (22.6-27.2)	23.9 (22.2-25.4)	0.5011
25(OH)D (ng/mL), median IQR	24.3 (20.0-29.5)	24.6 (22.6-28.4)	22.55 (19.1-29.4)	0.1161
25(OH)D dichotomous
Low, median IQR	19.8 (17.3-22.0)	21.70 (19.4-22.6)	19.1 (15.9-20.2)	0.014
High, median IQR	27.9 (25.3-33.0)	27.3 (25.4-30.9)	30.7 (25.2-36.0)	0.187
25(OH)D status				0.009
Non-deficiency	75 (76.5)	36 (90.0)	39 (67.24)
Deficiency	23 (23.5)	4 (10.00)	19 (32.76)

¹P if the variable is continuous, it is obtained by the Kruskal Wallis rank sum test. If the counting variable has a theoretical number < 10, it is obtained by Fisher’s exact probability test.

DD: Duration of diabetes; UA: Serum uric acid; FPG: Fasting plasma glucose; HbA1c: Glycated hemoglobin; ALB: Albumin; BMI: Body mass index; IQR: Interquartile range; 25(OH)D: 25-hydroxyvitamin D.

Table 2 Univariate analysis for first metatarsophalangeal joint synovial hypertrophy across different degrees

Variable	OR (95%CI)	P value
Gender
Male	Reference
Female	0.95 (0.41, 2.18)	0.8962
Age (year)	0.95 (0.91, 0.99)	0.0146
DD (year)	1.00 (0.95, 1.06)	0.9327
UA (μmol/L)	1.00 (0.99, 1.01)	0.7669
FPG (μg/dL)	1.06 (0.88, 1.27)	0.5511
HbA1c (%)	0.97 (0.79 1.20)	0.7817
ALB (g/L)	1.16 (1.03, 1.32)	0.0183
BMI (kg/m2)	0.94 (0.83, 1.07)	0.3633
25(OH)D (ng/mL)	0.96 (0.91, 1.02)	0.2169
25(OH)D (dichotomous)
Low	0.85 (0.75, 0.98)	0.0229
High	1.01 (0.93, 1.10)	0.8308
25(OH)D status
Non-deficiency	Reference
Deficiency	4.38 (1.36, 14.12)	0.0132

DD: Duration of diabetes; UA: Serum uric acid; FPG: Fasting plasma glucose; HbA1c: Glycated hemoglobin; ALB: Albumin; BMI: Body mass index; 25(OH)D: 25-hydroxyvitamin D; OR: Odds ratio; CI: Confidence interval.

Table 3 Multivariate analysis of serum 25-hydroxyvitamin D in the degree of first metatarsophalangeal joint synovial hypertrophy

Variable	Model I		Model II
	OR (95%CI)	P value	OR (95%CI)	P value
25(OH)D (dichotomous)
Low	0.83 (0.72, 0.97)	0.0152	0.83 (0.71, 0.97)	0.0163
High	1.01 (0.92, 1.11)	0.8054	1.02 (0.92, 1.13)	0.7081
25(OH)D status
Non-deficiency	Reference		Reference
Deficiency	3.68 (1.01, 13.39)	0.0484	3.86 (1.05, 14.20)	0.0422

Model I: Age and albumin were adjusted. Model II: Age, albumin, duration of diabetes, body mass index, and gender were adjusted. 25(OH)D: 25-hydroxyvitamin D; OR: Odds ratio; CI: Confidence interval.

Table 4 Threshold effect of serum 25-hydroxyvitamin D on the degree of synovial hypertrophy of the first metatarsophalangeal joint using the segmentation logistic regression model

Inflection points of 25(OH)D (ng/mL)	OR (95%CI)	P value
< 23.8	0.79 (0.67, 0.94)	0.0078
> 23.8	1.06 (0.96, 1.17)	0.2465
Log-likelihood ratio test		0.007

Adjusted: Age and albumin. 25(OH)D: 25-hydroxyvitamin D; OR: Odds ratio; CI: Confidence interval.