Cystatin C is a sensitive marker for detecting a reduced glomerular filtration rate when assessing chronic kidney disease in patients with rheumatoid arthritis and secondary amyloidosis

Factors contributing to discrepant estimated glomerular filtration values measured by creatinine and cystatin C in patients with rheumatoid arthritis

This study aimed to clarify the factors underlying the discrepancy that has been noted between estimated glomerular filtration ratio (eGFR) measured using serum creatinine (Cr) and eGFR using serum cystatin C (CysC) in patients with rheumatoid arthritis (RA) and to identify those patients whose renal function should be evaluated using CysC. We retrospectively evaluated clinical features, disease activity, Steinbrocker radiological staging, and co-morbidities (diabetes mellitus, hypertension, dyslipidemia) in 238 RA patients. eGFR using serum creatinine (eGFR-Cr) and eGFR using serum cystatin C (eGFR-CysC) were calculated using the new Japanese coefficient-modified Modification of Diet in Renal Disease study equation. To clarify the cause(s) of differences of 20% or more between the two eGFRs, we divided our RA patients into Group A (eGFR-Cr/eGFR-CysC ≥ 1.2) and Group B (eGFR-Cr/eGFR-CysC < 1.2), and searched for factors independently related to Group A. Forty-five patients (18.9%) were assigned to Group A, and 193 (81.1%) to Group B. BMI (Odds Ratio [OR] 0.820, 95% confidence interval [CI] 0.675–0.996), Hb (OR 0.633, 95% CI 0.433–0.926), CK (OR 0.773 per 10 units, 95% CI 0.644–0.933), NSAID use (OR 0.099, 95% CI 0.020–0.494), diabetes mellitus (OR 6.024, 95% CI 1.508–24.390) and stage 4 Steinbrocker radiological stage (OR 10.309, 95% CI 2.994–35.714) were identified as independent relevant factors for Group A by a multifactorial analysis. Renal function in RA patients with low BMI, diabetes, anemia and low CK may be overestimated using eGFR-Cr alone, and such patients need to be evaluated using eGFR-CysC.

Renal dysfunction among rheumatoid arthritis patients: A retrospective cohort study

Background

Rheumatoid arthritis (RA) is a common rheumatological disease which can involve a variety of different renal manifestations. This may be explained by disease effect itself or by medications used for treatment that may lead to renal dysfunction and its complications.

We aimed to identify the prevalence and factors that played a role in renal dysfunction among RA Jordanian patients.

Method

285 patients with RA visiting outpatient clinic between March 2016 and March 2017 were included in a retrospective study design. Age, gender, comorbidities, duration of the disease, medications and laboratory results were gathered and scoring of RA activity was done.

Results

Data gathered from the 285 patients showed a female predominance with 88.4% female and 11.6% male. The average disease duration was 6.7 years. Age, DM, HTN, and serum CRP were associated with worse renal function on univariate analysis. 44 patients (18.8%) presented with microscopic hematuria, 16 (6.9%) with proteinuria and only 5 (2.1%) patients presented with both microscopic hematuria and proteinuria. Patients with eGFR <60 ml/min had longer disease duration with a mean of 11 years (±7.7) in comparison to 6.4 years (±6.1) for those with eGFR>90 ml/min (P = 0.001).

Conclusion

Renal dysfunction is not common in RA Jordanian population and has variable presentations. Age and the duration of illness play a major role in the progression of CKD if present. Future prospective studies evaluating renal biopsies in RA patients are needed.

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First study in the country to discuss the prevalence of renal involvement in rheumatoid arthritis.

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Renal involvement is rare in rheumatoid arthritis patients.

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Different drugs can affect renal outcome in a different ways.

Utility of estimated glomerular filtration rate using cystatin C and its interpretation in patients with rheumatoid arthritis under glucocorticoid therapy

BACKGROUND

Patients with rheumatoid arthritis (RA) often have reduced muscle mass. Estimated glomerular filtration ratio using the serum cystatin C concentration (eGFRcys) is more accurate than eGFR using the serum creatinine (eGFRcreat) because cystatin C is not influenced by muscle mass, but glucocorticoid therapy may affect serum cystatin C concentration.

METHODS

Fifty patients with RA were included in this study. Renal inulin clearance (Cin) was measured and compared with eGFRcreat, eGFRcys, or the mean of eGFRcreat and eGFRcys (eGFRavg).

RESULTS

The mean creatine kinase (CK) concentration was low (36.8 ± 24.4 U/l).The eGFRcreat and eGFRcys regression lines were significantly different from y = x. The mean eGFRcreat value was significantly higher than Cin and that of eGFRcys was lower than Cin. The difference between eGFRcys and Cin was negatively correlated with daily PSL dose. The mean eGFRcys value of patients taking <10 mg PSL was not different from Cin and the eGFRcys regression line was not different from y = x.

CONCLUSION

eGFRcys of patients taking a daily PSL dose ≥10 mg was inaccurate, while eGFRcys was underestimated. eGFRcys was more accurate than eGFRcreat or eGFRavg for patients taking a daily PSL dose of <10 mg.

Serum Fibroblast Growth Factor 23 (FGF23) in Patients with Rheumatoid Arthritis

Objective Rheumatoid arthritis (RA) is a chronic inflammatory disease accompanied by periarticular and systemic osteoporosis. Fibroblast growth factor 23 (FGF23), which is mainly produced by osteocytes, circulates to the kidneys and regulates bone metabolism. We herein assessed serum FGF23 and its relationship to inflammation and osteoporosis in patients with RA. Methods Sixty-one patients with RA were included. Serum concentrations of FGF23 were determined using a sandwich enzyme-linked immunosorbent assay. Results The mean (± standard deviation) serum FGF23 concentration was 34.9±9.2 (range, 21.0-61.0) pg/mL. The serum FGF23 level was significantly and positively correlated with the erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) levels, disease activity score-28 based on the ESR (DAS-28 ESR) and DAS-28 CRP (r=0.261, p=0.044, r=0.280, p=0.029, r=0.409, p=0.001 and r=0.421, p=0.001, respectively). The serum matrix metalloproteinase-3 level was also significantly and positively correlated with the serum FGF23 level (r=0.331, p=0.015). Concentrations of type I collagen cross-linked N-telopeptide in the serum was significantly correlated with the serum FGF23 level (r=0.272, p=0.034). Neither the bone mineral density in the femoral neck nor lumbar was significantly correlated with the serum FGF23 level. Serum phosphate, calcium, 25-hydroxy vitamin D, and intact parathyroid hormone were not related to the serum FGF23 level. Conclusion In patients with RA, serum FGF23 is correlated with inflammation, the disease activity of RA, and bone absorption markers. Serum FGF23 may be associated with abnormal bone absorption related to RA inflammation. Further studies are necessary to clarify the mechanism underlying this association.

Biochemical markers in early diagnosis and management of systemic amyloidoses

Systemic amyloid diseases are characterized by widespread protein deposition as amyloid fibrils. Precise diagnostic framing is the prerequisite for a correct management of patients. This complex process is achieved through a series of steps, which include detection of the tissue amyloid deposits, identification of the amyloid type, demonstration of the amyloidogenic precursor, and evaluation of organ dysfunction/damage. Laboratory medicine plays a central role in the diagnosis and management of systemic amyloidoses, through the quantification of the amyloidogenic precursor and evaluation of end-organ damage using biomarkers.

Serum cystatin C is not an appropriate marker for kidney involvement in patients with primary Sjögren's syndrome

OBJECTIVES

We aimed to investigate serum cystatin C (cysC) levels in primary Sjögren's syndrome (pSS) patients, and evaluate its correlation with renal involment.

MATERIALS AND METHODS

Eighty-six pSS patients and 65 age- and gender-matched healthy controls were enrolled into the study. Serum cysC, urea, serum creatinine (SCr), creatinine clearance (CrCl), glomerular filtration rates (GFR), Na, K, Mg, Ca, uric acid, P, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), anti-Ro/SS-A, anti-La/SS-B, antinuclear antibodies, 24-h urinary poteinuria and microalbuminuria were evaluated.

RESULTS

Mean serum cysC levels did not differ between the patients and healthy controls (P > 0.05). Nine patients with pSS had proteinuria over 150 mg (and microalbuminuria over 30 mg) per 24 h. In patients with proteinuria, serum cysC levels correlated with serum K (r = 0.279, P = 0.024), ESR (r = 0.405, P = 0.001) and the disease duration (r = 0.235, P = 0.04), respectively. Patients with positive anti-Ro/SS-A and anti-La/SS-B antibodies had higher SCr levels compared to those with negative serology (r = 0.292, P = 0.009, and r = 0.259, P = 0.022, respectively). Nine patients with proteinuria and anti-Ro/SS-A, anti-La/SS-B positivity tended to have lower K and Mg levels which suggests subclinical renal tubular acidosis.

CONCLUSION

There were no associations between serum cysC levels and renal involvement in patients with pSS. However, in patients with proteinuria, serum cysC levels were correlated with acute-phase reactants, suggesting an association with disease activity in terms of degree of inflammation.

Age-dependent decline in renal function in patients with lung cancer

The aim of this study was to clarify the effect of aging on renal function. Serum creatinine (SCr), blood urea nitrogen (BUN) and 24-h creatinine clearance (measured-CrCl) were examined in lung cancer patients and the measured-CrCl were compared with CrCl estimates by employing two commonly used equations. In total, 787 lung cancer patients who were diagnosed between 2001 and 2010 were retrospectively analyzed. SCr and urine creatinine, BUN and measured-CrCl were evaluated prior to treatment. The Cockcroft-Gault (CG) and modification of diet in renal disease (MDRD) formulae were also used to estimate CrCl. SCr, BUN and measured-CrCl showed a significant decline in the elderly. In the 787 lung cancer patients, a significant correlation coefficient was found between measured-CrCl and age. However, in patients aged 80 years or older, no significant correlation coefficient was found between measured-CrCl and age. In the comparison between the measured CrCl and the CrCls estimated by the two formulae, the CG-CrCl levels were lower than those of the measured-CrCl, whereas the MDRD-CrCl levels were higher. Age is a crucial factor influencing renal function in patients with lung cancer. Particularly in the elderly, a decline in CrCl and greater individual variability in CrCl, as well as discrepancies in measured-CrCl and estimated CrCls are significant factors.

The challenge of systemic immunoglobulin light-chain amyloidosis (Al)

The cardiac involvement and associated mortality that occur in systemic AL amyloidosis remain among the most challenging aspects of the systemic amyloid-related diseases. Monoclonal immunoglobulin light chains produced by a clone of plasma cells are usually the cause of symptoms and organ dysfunction via both poorly understood toxic effects of misfolded species and accumulation of interstitial amyloid fibrils in key viscera. Treatment is aimed at eliminating the clonal cells in order to eliminate toxic light chain production. Recent advances in therapy have helped many patients with AL achieve complete hematologic responses and significant reversal of organ damage but these benefits do not extend to that 10-15 % who present with advanced cardiac involvement. Even with cardiac transplant followed by effective therapy such as stem cell transplant, outcomes for these patients remain promising at best.

Cystatin C concentration is correlated with disease activity in rheumatoid arthritis patients

OBJECTIVES

Rheumatoid arthritis (RA) is a systemic, inflammatory disease. Renal involvement worsens the course of RA and increases mortality. It is suggested that chronic inflammatory processes may contribute to renal impairment. The aim of this study was to investigate the impact of chronic inflammation and RA activity on glomerular filtration rate (GFR).

METHODS

The study population consisted of 140 RA patients. High disease activity was observed in 42 patients (30%), and long-term RA (duration ≥ 10 years) in 64 (45.7%). Measures of renal function included: serum cystatin C, serum creatinine (SCr), and creatinine-based estimated GFR (eGFR) calculated by Cockcroft and Gault (CG) and Modification of Diet in Renal Disease (MDRD) formulas.

RESULTS

The mean (SD) cystatin C concentration was 0.77 (0.2) mg/L, SCr 0.71 (0.23) mg/dL, eGFR(CG) 110.5 (37.8) mL/min/1.73 m², and eGFR(MDRD) 109.5 (34.5) mL/min/1.73 m². Cystatin C levels correlated positively with creatinine, and negatively with eGFR(CG) and eGFR(MDRD). Cystatin C concentration was significantly higher in patients with high disease activity, long-term RA, and hypertension, and in males. Patients currently being treated with biologics had non-significantly lower cystatin C levels than those treated with conventional modifying drugs. Cystatin C levels were significantly associated with markers of clinical, functional disease activity, and markers of inflammation. By contrast, there were no such correlations with other parameters of renal function.

CONCLUSIONS

In patients with RA, cystatin C may be not only an indicator of GFR but also a marker of intensity of chronic inflammatory processes.