Background The prevalence of chronic kidney disease (CKD) in general population is about 10%.
Objectives The aim of this study was to determine the prevalence of CKD in patients with rheumatoid arthritis (RA) and factors associated with its occurrence.
Methods 155 unselected patients (138 women and 17 men) with RA fulfilling 1987 ACR criteria were enrolled in the study. A detailed medical history, including course and treatment of RA was taken. The physical examination and laboratory analysis were performed in each subject. An ultrasonography of the abdomen was performed in 123 patients.
The diagnosis of CKD was established according to Kidney Diseases Outcome Quality Initiative (KDOQI) and based on either presence of kidney damage or decreased glomerular filtration rate (GFR) <60 ml/min/1.73m2 for at least 3 months. Kidney damage was defined as structural or functional abnormalities of the kidney with or without decreased GFR, manifest by pathologic abnormalities or markers of kidney damage, including abnormalities in composition of the blood or urine or abnormalities in imaging studies.
Stages of CKD was assigned based on the level of kidney function (estimated GFR), according to the KDOQI CKD classification. The level of GFR was estimated by Modification of Diet in Renal Disease Study equation (MDRD).
Results The mean age was 60.5 (±12.1) years. The mean RA duration was 10.4 (±9.5) years. The mean serum creatinine concentration was 0.74 (±0.24) mg/dl. The mean GFR was 90.4 (±20.9) ml/min/1.73m2.
CKD was diagnosed in 56 patients (36%), of whom 48 had kidney damage with or without decreased GFR and 8 had decreased GFR<60 ml/min/1.73m2 without kidney damage. Among patients with kidney damage 7 had abnormal blood tests, 17 had abnormal urine tests and 37 had abnormalities in ultrasonography of the abdomen.
Among CKD patients, 21 (37.5%) had first, 18 (32.1%) had second, 16 (28.6%) had third and 1 (1.8%) had fourth stage of the disease.
Significantly higher prevalence of CKD was observed in RA patients with presence of extra-articular manifestations (76% vs 52%, p- 0.004), elevated ESR (67% vs 51%, p- 0.05), higher radiological stage of the disease (p- 0.04) and co-existing hypertension (69% vs 51%, p- 0.04). There were also significant differences in mean age (64 vs 59 years, p- 0.009), mean RA duration (13.2 vs 8.5 years, p-0.008) and mean hemoglobin level (11.9 vs 12.5 g/dl, p- 0.03) between patients with and without CKD.
No statistically significant difference was found between these two groups for gender, smoking status, RA activity indices (tender and swollen joints count, DAS28, HAQ) and serological markers (RF, ACPA, ANA).
Additionally, we analyzed association between level of kidney function and demographic factors, smoking status, RA activity indices and treatment, laboratory and serological tests results. We found a significantly lower value of estimated GFR in patients with older age (p- 0.0000001), longer RA duration (p- 0.05), presence of extra-articular manifestations (p- 0.02), co-existing hypertension (p- 0.0000001), lower methotrexate dose (p- 0.003) and in methotrexate naïve patients (p- 0.003).
Conclusions Our study showed a great percentage of CKD in patients with RA. The obtained results suggested that older age, long-standing, severe disease with extra-articular manifestations, inappropriate RA treatment and co-existing hypertension increased risk of CKD in patients with RA.
Disclosure of Interest None declared