**3. Experience from Serbian National APS Registry**

#### **3.1. Patients and methods**

Study included a total of 137 APS patients, attending outpatient clinic of the University Medical Center Bezanijska kosa, all Caucasians, who were previously enrolled in Serbian National APS Registry. These patients represented only the part of those so far included in this Registry, which is still growing and is still unable to appraise the prevalence of APS among general population in Serbia. Among studied patients, 68 were PAPS patients (59 females, nine males, mean age 43.51+10.58 years) and 69 sAPS patients (61 females, eight males; mean age 47.83+15.67 years). All studied APS patients have met 2006 updated Sydney criteria [5] which requested the presence of at least one clinical criteria (i.e. vascular thrombosis or multiple and recurrent foetal losses) and at least one of antiphospholipid antibodies (aPL), i.e. lupus anticoagulant (LA), anticardiolipin (aCL) and/or anti‐β2‐glycoprotein 1 (β2GP1) antibodies. Most of our sAPS patients had APS associated with systemic lupus erythematosus (SLE) (n=60; 87%), while the rest had Sjögren's syndrome (n=8; 11.5%) and ankylosing spondylitis (n=1; 1.5%). Mean duration of these rheumatic diseases in sAPS patients was 5.69+2.87 years, ranging from 1 to 13 years.

Characteristics of two subgroups of APS patients were compared with 50 MetS patients (35 females, 15 males; mean age 47.68+11.66 years). The presence of metabolic syndrome among studied patients was determined according to the International Diabetes Federation (IDF) clinical definition [12]. An obligatory criterion for MetS requested by this definition is ab‐ dominal obesity defined by elevated waist circumference (WC) with gender‐ and ethnic‐ specific cut‐offs, meaning 94 cm for males, and 80 cm for females belonging to European population. Besides abdominal obesity, two or more of the four additional criteria (a) hyper‐ triglyceridemia >150 mg/L, confirmed or already treated; (b) high density lipoprotein (HDL) cholesterol <40 mg/dL in males or <50 mg/dL in females; (c) blood pressure >130/85 mmHg, newly diagnosed or already treated; (d) impaired fasting glycaemia, >100 mg/dL or previously diagnosed diabetes) are necessary for the diagnosis.

For every participant, clinical data concerning thrombotic events, their appearance, manage‐ ment and follow‐up were obtained from medical charts review. As thrombotic events, the following were recorded: superficial and deep venous thrombosis, pulmonary embolism, peripheral arterial occlusion, cerebral vascular accident and myocardial infarction.

After an overnight fast, height (m), weight (kg) and waist circumference (cm) were measured in every participant with underwear and without shoes. Waist circumference (WC) was measured at the level of the umbilicus while the participant was standing and breathing normally. Body mass index (BMI) was calculated according to the widely accepted formula dividing body weight by the square of individual's height. Morning samples of venous blood (3–5 mL) were withdrawn from every participant for the analysis of serum glucose and lipids. Serum vitamin D levels were determined in every participant .

The study was approved by the Institutional Ethics Committee. All examinations were conducted according to the most recent amendment of Declaration of Helsinki (Edinburgh, 2000), only after obtaining an informed consent for participation in the study from every subject.

Statistical analysis was performed using the STATISTICA 10 software program. Descriptive statistics was used. Prevalence of MetS as well as of its individual components, within studied groups of patients was expressed as percentage. Testing significance of their differences, the Student's t‐test and Fisher's exact test were used, considering p value <0.05 statistically significant.

#### **3.2. Results**

Similar ambiguity exists concerning the definition of adequate circulating VitD level, as well as of its deficiency and insufficiency. Earlier definition of VitD insufficiency by its blood level of <20 ng/mL (50 nmol/L), given by the World Health Organization (WHO) [14], has been recently accepted by most researchers as a definition of the deficiency of this vitamin [15, 16]. Its insufficiency is defined as a VitD concentration between 20 and 30 ng/mL (50 and 75 nmol/

**Central obesity** *plus 2 of:*

Study included a total of 137 APS patients, attending outpatient clinic of the University Medical Center Bezanijska kosa, all Caucasians, who were previously enrolled in Serbian National APS Registry. These patients represented only the part of those so far included in this Registry, which is still growing and is still unable to appraise the prevalence of APS among general population in Serbia. Among studied patients, 68 were PAPS patients (59 females, nine males, mean age 43.51+10.58 years) and 69 sAPS patients (61 females, eight males; mean age 47.83+15.67 years). All studied APS patients have met 2006 updated Sydney criteria [5] which requested the presence of at least one clinical criteria (i.e. vascular thrombosis or multiple and recurrent foetal losses) and at least one of antiphospholipid antibodies (aPL), i.e. lupus anticoagulant (LA), anticardiolipin (aCL) and/or anti‐β2‐glycoprotein 1 (β2GP1) antibodies. Most of our sAPS patients had APS associated with systemic lupus erythematosus (SLE) (n=60; 87%), while the rest had Sjögren's syndrome (n=8; 11.5%) and ankylosing spondylitis (n=1; 1.5%). Mean duration of these rheumatic diseases in sAPS patients was 5.69+2.87 years, ranging

Characteristics of two subgroups of APS patients were compared with 50 MetS patients (35 females, 15 males; mean age 47.68+11.66 years). The presence of metabolic syndrome among studied patients was determined according to the International Diabetes Federation (IDF) clinical definition [12]. An obligatory criterion for MetS requested by this definition is ab‐ dominal obesity defined by elevated waist circumference (WC) with gender‐ and ethnic‐ specific cut‐offs, meaning 94 cm for males, and 80 cm for females belonging to European population. Besides abdominal obesity, two or more of the four additional criteria (a) hyper‐

L), while its concentrations >30 ng/mL (75 nmol/L) are regarded as sufficient [17, 18].

**The WHO definition10 NCEP ATP III definition11 IDF definition12**

Atherogenic dyslipidaemia

Hypertension Microalbuminuria Impaired fasting glucose/Glucose intolerance/Diabetes

**3. Experience from Serbian National APS Registry**

≥ *3 of:*

**Table 2.** Metabolic syndrome definitions—similar but different enough.

**Insulin resistance** *plus ≥ 2 of:*

184 A Critical Evaluation of Vitamin D - Clinical Overview

**3.1. Patients and methods**

from 1 to 13 years.

#### *3.2.1. Prevalence of MetS among patients with APS*

Metabolic syndrome was observed in high percentage of patients with APS. Its prevalence did not differ significantly between PAPS (36.76%) and sAPS (42.03%) patients (p=0.53).

Anthropometric and metabolic syndrome characteristics among studied groups are given in **Table 3**. Borderline statistical significance of the difference in WC value was observed when two subgroups of APS patients were compared with MetS patients (F=2.77, p=0.065), while BMI has differed highly significantly between these groups (F=9.765, p=0.0001). In spite of slightly lower BMI and slightly higher WC in PAPS patients, neither BMI (p=0.434) nor WC (p=0.275) did differ significantly between two subgroups of APS patients.

Atherogenic dyslipidaemia, represented by hypertriglyceridemia and low HDL cholesterol, was the most prevalent characteristic of metabolic syndrome among PAPS patients. In spite of this, prevalence of low HDL cholesterol among PAPS patients were significantly lower than in MetS patients (48.3% vs. 70%, p=0.02). Prevalence of hypertriglyceridemia (45.59% vs. 42.03%, p=0.67) and low HDL cholesterol (48.53% vs. 53.62%, p=0.55) did not differ significantly between PAPS and sAPS patients. Hypertension was significantly less prevalent among these patients compared with MetS (23.53% vs. 58%, p=0.0002) and even with sAPS (23.53% vs. 52.17%, p=0.0007) patients. The least prevalent characteristic of metabolic syndrome among patients with APS was hyperglycaemic disorder. Compared with MetS patients in whom impaired fasting glycaemia, glucose intolerance or diabetes were present in as much as 36%, these disorders were observed in only 5.88% of PAPS patients (p=0.0001) and 4.35% of sAPS patients (p<0.0001).


\*\*p < 0.01, PAPS vs. MetS. # p < 0.01, sAPS vs. MetS. § p < 0.01, PAPS vs. sAPS.

**Table 3.** Anthropometric and metabolic syndrome characteristics among studied groups.

#### *3.2.2. Prevalence of thrombotic events among APS patients with or without MetS*

Compared with patients with metabolic syndrome, prevalence of thrombotic events was significantly higher among patients with PAPS (52.94% vs. 22%, p=0.0009) and sAPS (56.52% vs. 22%, p=0.0003). Thrombotic events were reported with similar prevalence in PAPS and sAPS patients (p=0.674).

When compared with APS patients without characteristics of MetS, thrombotic events were significantly more frequent among MetS positive patients with sAPS (75.86% vs. 42.5%, p=0.0075).

Although higher among MetS positive, compared with MetS negative patients with PAPS, difference of prevalence of thrombotic events among these two subgroups of PAPS patients did not reach statistical significance (68% vs. 44.19%, p=0.0622).

#### *3.2.3. Vitamin D status among APS patients depending on MetS and/or thrombotic events*

Low VitD status (insufficiency or deficiency) was highly prevalent among PAPS (insufficiency in 27.94% and deficiency in 36.76%) and sAPS patients (insufficiency in 30.43% and deficiency in 40.58%), as well as among patients with pure MetS (insufficiency in 20% and deficiency in 32%).

In comparison with patients with pure MetS (28.58*+*14.32 ng/mL), VitD concentrations were lower in PAPS (25.76*+*12.18 ng/mL) and sAPS patients (23.81*+*11.22 ng/mL), but with statisti‐ cally significant difference only between these concentrations in sAPS patients and patients only with MetS (p=0.04).

42.03%, p=0.67) and low HDL cholesterol (48.53% vs. 53.62%, p=0.55) did not differ significantly between PAPS and sAPS patients. Hypertension was significantly less prevalent among these patients compared with MetS (23.53% vs. 58%, p=0.0002) and even with sAPS (23.53% vs. 52.17%, p=0.0007) patients. The least prevalent characteristic of metabolic syndrome among patients with APS was hyperglycaemic disorder. Compared with MetS patients in whom impaired fasting glycaemia, glucose intolerance or diabetes were present in as much as 36%, these disorders were observed in only 5.88% of PAPS patients (p=0.0001) and 4.35% of sAPS

) 32.09*+*6.14 27.81*+*5.98 28.54+4.22

**WC** (cm) 93.67*+*14.36 90.73*+*9.18 88.53*+*11.91 **TG > 150 mg/dL** (%) 58 45.59 42.03 **HDL < 40/50 mg/dL** (%) 70 48.53\*\* 53.62 **Hypertension** (%) 58 23.53\*\*\*\* 52.17§§ **IFG, IGT, DM** (%) 36## 5.88\*\*\*\* 4.35

**Table 3.** Anthropometric and metabolic syndrome characteristics among studied groups.

did not reach statistical significance (68% vs. 44.19%, p=0.0622).

*3.2.2. Prevalence of thrombotic events among APS patients with or without MetS*

Compared with patients with metabolic syndrome, prevalence of thrombotic events was significantly higher among patients with PAPS (52.94% vs. 22%, p=0.0009) and sAPS (56.52% vs. 22%, p=0.0003). Thrombotic events were reported with similar prevalence in PAPS and

When compared with APS patients without characteristics of MetS, thrombotic events were significantly more frequent among MetS positive patients with sAPS (75.86% vs. 42.5%,

Although higher among MetS positive, compared with MetS negative patients with PAPS, difference of prevalence of thrombotic events among these two subgroups of PAPS patients

Low VitD status (insufficiency or deficiency) was highly prevalent among PAPS (insufficiency in 27.94% and deficiency in 36.76%) and sAPS patients (insufficiency in 30.43% and deficiency in 40.58%), as well as among patients with pure MetS (insufficiency in 20% and deficiency in

*3.2.3. Vitamin D status among APS patients depending on MetS and/or thrombotic events*

**MetS PAPS sAPS**

patients (p<0.0001).

186 A Critical Evaluation of Vitamin D - Clinical Overview

p < 0.05, PAPS vs. MetS. \*\*p < 0.01, PAPS vs. MetS.

p < 0.01, sAPS vs. MetS.

p < 0.01, PAPS vs. sAPS.

sAPS patients (p=0.674).

p=0.0075).

32%).

**BMI** (kg/m2

\*

#

§

Significantly lower VitD level was observed in those with coexisting MetS (MetS +), compared with those without it (MetS ‐) both in PAPS (MetS +: 22.0*+*8.52 vs. MetS ‐: 27.0*+*13.49 ng/mL, p=0.05 ) and sAPS patients (MetS +: 18.83*+*9.16 vs. MetS ‐: 27.42*+*11.28 ng/mL, p=0.0012).

Also, significantly lower VitD level was observed in APS patients with thrombotic events (TE+), compared with those without these events (TE ‐), both in PAPS (TE +: 20.61+12.18 vs. TE ‐: 31.56*+*12.72 ng/mL, p=0.0001 ) and sAPS patients (TE +: 20.67*+*10.43 vs. TE ‐: 27.9*+*11.04  ng/mL, p=0.007).

In 11 (22%) of patients with MetS, but without APS, some thrombotic event was confirmed. In those patients, VitD levels were also significantly lower than in those without these events (TE +: 18.45*+*10.66 vs. TE ‐: 31.43*+*13.63 ng/mL, p=0.003).

However, both in PAPS and sAPS patients, with coexisting MetS, previous thrombotic events did not influence serum VitD levels (PAPS: p=0.12; SAPS: p=0.93).
