Association between serum Cystatin C and renal injury in patients with chronic hepatitis B.

To explore the association between serum cystatin C (Cys-C) and renal damage in patients with chronic hepatitis B.We retrospectively analyzed the clinical data of 425 patients with chronic hepatitis B virus (HBV) infection. Liver stiffness measured by FibroScan was used to diagnosis liver fibrosis. Cys-C levels were detected via latex-enhanced immunoturbidimetric assay.A total of 425 patients were enrolled. Among them, 217 were patients with CHB with an eGFR > 90 mL/min/1.73 m and 208 with an eGFR ≤90 mL/min/1.73 m. Cys-C levels significantly differed in patients with eGFR > 90 mL/min/1.73 m compared with patients with eGFR ≤90 mL/min/1.73 m (0.81 ± 0.05 vs 1.05 ± 0.06 mg/L, P < .001). Moreover, the Cys-C levels were 0.82 ± 0.04 mg/L in patients without liver fibrosis, 0.98 ± 0.05 mg/L in patients with mild liver fibrosis, 1.05 ± 0.08 mg/L in patients with advanced liver fibrosis, and 1.12 ± 0.07 mg/L in patients with liver cirrhosis (P < .001). Multivariate analyses were conducted to explore the independent factors associated with a decreased eGFR. Multivariate analysis suggested that T2DM (P = .032), liver fibrosis (P = .013), and Cys-C level (P = .035) were the independent factors associated with the decreased eGFR in patients with CHB. While age (P = .020) and Cys-C level (P = .001) were the independent factors associated with the decreased eGFR in patients with CHB-related fibrosis.The fibrosis group had significantly higher Cys-C levels than those without fibrosis. Routine monitoring of Cys-C levels is of positive significance in preventing the development of renal impairment of CHB patients.

Introduction

Chronic hepatitis B virus (HBV) infection is an important cause of liver cirrhosis.[ Studies have reported that patients with chronic hepatitis B (CHB) and liver cirrhosis have different degrees of renal injury as the disease progresses.[ A variety of mechanisms can induce renal function injury in patients with CHB.[ Studies have reported that, after the hemodynamic changes, renal injury will further reduce the glomerular filtration rate (GFR) and therefore increase the mortality rate.[

At present, the serum creatinine level and estimated GFR (eGFR) commonly used in clinical practice cannot accurately and sensitively reflect early renal damage.[ Serum cystatin C (Cys-C), as a biomarker of renal injury, is a more specific and sensitive endogenous indicator.[ However, no study has reported the association between Cys-C levels and renal damage among patients with CHB.

Hence, this study analyzed the level of Cys-C and liver fibrosis in patients with chronic HBV infection and explored the association of Cys-C with renal injury in patients with CHB to improve early identification of renal damage in this population.

Subjects and methods

Subjects

This study used a retrospective analysis. We included patients with chronic HBV infection from January 1, 2017 to December 31, 2018. Patients were included if they were 18 years of age or older and tested positive for hepatitis B surface antigen >6 months. Patients with kidney stones, kidney cysts, and other diseases causing kidney damage were excluded. This research was approved by the Ethics Committee of Qingdao Sixth People's Hospital, and all patients signed the informed consent.

Data collection

We used a questionnaire to collect data, including demographic data (sex, age, height, and weight) and laboratory test data. Liver stiffness measured by FibroScan was used to diagnosis liver fibrosis. HBV serological markers, HBV DNA quantification, and kidney-related detection markers, including creatinine and Cys-C, were also evaluated. According to FibroScan, the degree of liver fibrosis is classified as no fibrosis (liver stiffness <7.3 kPa), mild fibrosis (liver stiffness from 7.3 to 9.7 kPa), advanced fibrosis, (liver stiffness from 9.8 to 17.5 kPa), and liver cirrhosis (liver stiffness >17.5 kPa).[ GFR was estimated according to the MDRD formula: eGFR (mL/min/1.73 m2) = 175 × blood creatinine−1.234 × age−0.179 × 0.79 (if female).[ Cys-C levels were detected via latex-enhanced immunoturbidimetric assay according to manufacturer's protocol (Shanghai Junrui Biotechnology Co., Ltd.). According to the international guidelines recommended by the KDIGO organization, we define eGFR ≥ 90 mL/min/1.73 m2 as normal renal function.[

Statistical methods

Data were analyzed using SPSS 13.0 software. Normally distributed data are expressed as mean ± standard deviation. Comparisons between 2 groups were conducted using 2 independent samples t test. Multivariate forward Logistic Regression was conducted to evaluate risk factors associated with renal impairment. P < .05 was considered statistically significant.

Results

Patient demographics

A total of 425 patients were enrolled. Among them, 217 were patients with CHB with an eGFR >90 mL/min/1.73 m2 and 208 with an eGFR ≤90 mL/min/1.73 m2. The sex, age, alanine aminotransferase level, HBV DNA level, urea level, and proportion of hyperlipidaemia were similar for the two groups. There was a significantly higher proportion of patients diagnosed with type 2 diabetes mellitus (T2DM) in the group with eGFR ≤ 90 mL/min/1.73 m2 (Table 1).

Table 1

Baseline demographic and clinical characteristics by groups.

Renal function differs among patients with CHB

Cys-C levels significantly differed in patients with eGFR >90 mL/min/1.73 m2 compared with patients with eGFR ≤90 mL/min/1.73 m2 (0.81 ± 0.05 vs 1.05 ± 0.06 mg/L, P < .001) (Fig. 1). To further explore renal function in patients with CHB, we compared Cys-C level and eGFR in patients with different degrees of liver fibrosis. The results are shown in Figure 2. According liver stiffness values, 204, 124, 52, and 48 patients were diagnosed with no liver fibrosis, mild liver fibrosis, advanced liver fibrosis, and liver cirrhosis, respectively. The eGFR levels were, respectively, 105.3 ± 3.81, 104.4 ± 3.57, 97.17 ± 6.78, and 91.6 ± 5.15 mL/min/1.73 m2 (P < .001). The eGFR decreased with the severity of liver fibrosis. Similar results were observed for serum Cys-C levels. The Cys-C levels were 0.82 ± 0.04 mg/L in patients without liver fibrosis, 0.98 ± 0.05 mg/L in patients with mild liver fibrosis, 1.05 ± 0.08 mg/L in patients with advanced liver fibrosis, and 1.12 ± 0.07 mg/L in patients with liver cirrhosis (P < .001).

Figure 1

Cys-C levels in CHB patients with different eGFR level. Cys-C significantly differed in patients with eGFR >90 mL/min/1.73 m2 compared with patients with eGFR ≤90 mL/min/1.73 m2 (0.81 ± 0.05 vs 1.05 ± 0.06 mg/L, P < .001).

Figure 2

Cys-C levels in CHB patients with different degrees of liver fibrosis. A. The eGFR levels were 105.3 ± 3.81 mL/min/1.73 m2 in patients without liver fibrosis (n = 204), 104.4 ± 3.57 mL/min/1.73 m2 in patients with mild liver fibrosis (n = 124), 97.17 ± 6.78 mL/min/1.73 m2 in patients with advanced liver fibrosis (n = 52), and 91.6 ± 5.15 mL/min/1.73 m2 in liver cirrhosis (n = 48)(P < .001). B. The Cys-C levels were 0.82 ± 0.04 mg/L in patients without liver fibrosis, 0.98 ± 0.05 mg/L in patients with mild liver fibrosis, 1.05 ± 0.08 mg/L in patients with advanced liver fibrosis, and 1.12 ± 0.07 mg/L in patients with liver cirrhosis (P < .001).

Risk factors related to impaired renal function in all patients

Univariate and multivariate analyses were conducted to explore the independent factors associated with a decreased eGFR. The univariate analysis results showed that liver fibrosis, T2DM, and Cys-C level were the factors associated with the decrease in eGFR in patients with CHB. Multivariate analysis suggested that T2DM (P = .032), liver fibrosis (P = .013), and Cys-C level (P = .035) were the independent factors associated with the decreased eGFR in patients with CHB (Table 2).

Table 2

Risk factors for impaired renal function in CHB.

Risk factors related to impaired renal function in patients with liver fibrosis

Univariate and multivariate analyses were conducted to explore the independent factors associated with decreased eGFR in patients with CHB-related fibrosis. The multivariate analysis suggested that age (P = .020) and Cys-C level (P = .001) were the independent factors associated with the decreased eGFR in patients with CHB-related fibrosis (Table 3).

Table 3

Risk factors for impaired renal function in CHB with liver fibrosis.

Discussion

Chronic HBV infections not only lead to chronic liver damage but also can cause kidney damage through various mechanisms.[ When chronic hepatitis caused by HBV progresses to the stage of end-stage liver cirrhosis, portal hypertension further causes systemic hemodynamic changes and kidney damage, while kidney damage further aggravates portal hypertension, forming a vicious cycle. Previous studies[ have shown that 29% of patients with HBV-related nephritis will develop renal failure, of which 10% need renal replacement therapy for end-stage renal disease. Early kidney damage is not an organic change, and timely treatment can reverse kidney damage. A decreased GFR is considered the main manifestation of early kidney injury, but urea nitrogen and creatinine levels are susceptible to diet, body metabolic status, and the patient's muscle condition. The eGFR calculated based on this is not sufficiently sensitive or accurate for clinical diagnosis of early kidney injury.

Cys-C is a secreted protein whose amino acid sequence is stably expressed in most human tissues, and its production rate is stable in the body.[ It is not affected by factors such as eating status, disease factors, or muscle content and is almost completely filtered by the glomeruli. It is not reabsorbed by the renal tubules and is a new index for evaluating renal function.[ Previous research[ showed that Cys-C is significantly better than creatinine and urea nitrogen, and it can better reflect the change of GFR. This study analyzed Cys-C levels in patients with chronic HBV infection. As a result, eGFR levels in patients with cirrhosis were significantly lower than in those without fibrosis. The fibrosis group and liver cirrhosis group had significantly higher Cys-C levels than those without fibrosis. Moreover, T2DM, liver fibrosis and Cys-C level were the independent factors associated with the decreased eGFR in patients with CHB. While age and Cys-C level were the independent factors associated with the decreased eGFR in patients with CHB-related fibrosis.

It is suggested that with the progress of liver disease, renal damage in patients worsens.[ Cys-C level can detect renal damage earlier than eGFR, creatinine, or urea nitrogen. It was found that the level of Cys-C increased significantly in patients with liver cirrhosis. It is suggested that Cys-C may has early diagnostic significance for both chronic HBV infection. However, it needs further study to confirm. Previous studies have reported that CHB patients have impaired renal function compared to healthy controls.[ In our study, we further found that the renal function of CHB patients deteriorated further with the progression of liver fibrosis. Moreover, as eGFR decreases, the level of Cys-C will increase. Our research suggests that for patients with CHB, especially those with liver cirrhosis, detection of Cys-C and eGFR helps early warning of renal impairment.

This study had some limitations. All the patients were from one medical center, a prospective multicenter study is thus necessary. In our study, we failed to explore further the reasons why Cys-C and liver cirrhosis contributed to the decreased eGFR. We believe that a well-designed controlled study is needed to answer these questions.

In summary, our study found that eGFR levels in patients with cirrhosis were significantly lower than in those without fibrosis. The fibrosis group and liver cirrhosis group had significantly higher Cys-C levels than those without fibrosis. Moreover, T2DM, liver fibrosis and Cys-C level were the independent factors associated with the decreased eGFR in patients with CHB. While age and Cys-C level were the independent factors associated with the decreased eGFR in patients with CHB-related fibrosis. Routine monitoring of Cys-C levels is of positive significance in preventing the development of renal impairment of CHB patients.

Author contributions

HZ and DW designed and guided this study, HZ and HL conducted experiments and wrote the main manuscript text, AH and MZ prepared all figures and data analysis. All authors reviewed the manuscript.