Urine chloride self-measurement to monitor sodium chloride intake in patients with chronic kidney disease

Background Excessive sodium intake is a risk factor for hypertension, cardiovascular disease and the risk for kidney failure in chronic kidney disease (CKD) patients. Methods We tested the diagnostic performance and the feasibility of an inexpensive method based on urine chloride strips for self-monitoring sodium intake in a series of 72 CKD patients. Results Twenty-four hour urinary chloride as measured by the reactive strips and 24 h urinary sodium were interrelated (r=0.59, p<0.001). Forty-nine out of 72 patients (78%) had a 24 h urinary sodium >100 mmol/24 h, i.e. the upper limit recommended by current CKD guidelines. The strip method had 75.5% sensitivity and 82.6% specificity to correctly classify patients with urine sodium >100 mmol/24 h. The positive and the negative predictive values were 90.2% and 61.3%, respectively. The overall accuracy (ROC curve analysis) of urine chloride self-measurement for the >100 mmol/24 h sodium threshold was 87% (95% CI: 77%-97%). The large majority of patients (97%) perceived the test as useful to help compliance with the prescribed dietary sodium and considered the test as simple and of immediate application (58%) or feasible but requiring attention (39%). Conclusions A simple and inexpensive test for urine chloride measurement has a fairly good performance for the diagnosis of excessive sodium intake. The test is feasible and it is perceived by CKD patients as helpful for enhancing compliance to the dietary sodium recommendations. The usefulness of this test for improving hypertension control in CKD patients will be tested in a clinical trial (Clinicaltrials.gov RF-2010-2314890).

Reducing salt intake by urine chloride self-measurement in non-compliant patients with chronic kidney disease followed in nephrology clinics: a randomized trial

BACKGROUND

Adherence to low salt diets and control of hypertension remain unmet clinical needs in chronic kidney disease (CKD) patients.

METHODS

We performed a 6-month multicentre randomized trial in non-compliant patients with CKD followed in nephrology clinics testing the effect of self-measurement of urinary chloride (69 patients) as compared with standard care (69 patients) on two primary outcome measures, adherence to a low sodium (Na) diet (<100 mmol/day) as measured by 24-h urine Na (UNa) excretion and 24-h ambulatory blood pressure (ABPM) monitoring.

RESULTS

In the whole sample (N = 138), baseline UNa and 24-h ABPM were143 ± 64 mmol/24 h and 131 ± 18/72 ± 10 mmHg, respectively, and did not differ between the two study arms. Patients in the active arm of the trial used >80% of the chloride strips provided to them at the baseline visit and at follow-up visits. At the third month, UNa was 35 mmol/24 h (95% CI 10.8-58.8 mmol/24 h; P = 0.005) lower in the active arm than the control arm, whereas at 6 months the between-arms difference in UNa decreased and was no longer significant [23 mmol/24 h (95% CI -5.6-50.7); P = 0.11]. The 24-h ABPM changes as well as daytime and night-time BP changes at 3 and 6 months were similar in the two study arms (Month 3, P = 0.69-0.99; Month 6, P = 0.73-0.91). Office BP, the use of antihypertensive drugs, estimated Glomerular Filtration Rate (eGFR) and proteinuria remained unchanged across the trial.

CONCLUSIONS

The application of self-measurement of urinary chloride to guide adherence to a low salt diet had a modest effect on 24-h UNa and no significant effect on 24-h ABPM.

Urinary chloride concentration and progression of chronic kidney disease: results from the KoreaN cohort study for Outcomes in patients With Chronic Kidney Disease

BACKGROUND

Urinary chloride is regulated by kidney transport channels, and high urinary chloride concentration in the distal tubules can trigger tubuloglomerular feedback. However, little attention has been paid to urinary chloride as a biomarker of clinical outcomes. Here, we studied the relationship between urinary chloride concentration and chronic kidney disease (CKD) progression.

METHODS

We included 2086 participants with CKD from the KoreaN cohort study for Outcomes in patients With Chronic Kidney Disease. Patients were categorized into three groups, according to baseline urinary chloride concentration tertiles. The study endpoint was a composite of ≥50% decrease in estimated glomerular filtration rate from baseline values, or end-stage kidney disease.

RESULTS

During a median follow-up period of 3.4 years (7452 person-years), 565 participants reached the primary endpoint. There was a higher rate of CKD progression events in the lowest and middle tertiles than in the highest tertile. Compared with the lowest tertile, the highest tertile was associated with 33% [95% confidence interval (CI) 0.49-0.90] lower risk for the primary outcome in a cause-specific hazard model after adjustment for confounding variables. In addition, for every 25 mEq/L increase in urinary chloride concentration, there was 11% (95% CI 0.83-0.96) lower risk for CKD progression. This association was consistent in a time-varying model. Urinary chloride concentration correlated well with tubule function and kidney injury markers, and its predictive performance for CKD progression was comparable to that of these markers.

CONCLUSIONS

In this hypothesis-generating study, low urinary chloride concentration was associated with a higher risk for CKD progression.

Urine chloride trajectory and relationship with diuretic response in acute heart failure

AIMS

Sodium excretion is a well-defined marker used to assess diuretic response in acute heart failure (AHF). Despite a strong pathophysiological background, the role of urine chloride excretion has not been described and established yet. We aimed to evaluate chloride trajectory during intensive diuretic treatment in AHF patients and examine its potential role in predicting poor diuretic response.

METHODS

The study was conducted on 50 AHF patients. Participants were included within the first 36 h of hospitalization. They received furosemide dose adjusted for body weight (half in bolus, half in 2 h infusion). Post-diuretic hourly urine collection with biochemical analysis was performed.

RESULTS

In general, the concentrations of urine chloride (uCl-) and sodium (uNa+) at the baseline samples exhibited a comparable level (71 ± 39 vs. 70 ± 44 mmol/L, respectively; P = 0.99), but across all post-furosemide study timepoints, uCl- remained significantly higher than uNa+ since 1 to 6 h of the study. In this course, both ions (uCl- and uNa+) reached peak values in 2 h (114 ± 28 vs. 97 ± 34 mmol/L, respectively; P < 0.01). The pattern of uCl- dominance over uNa+ concentration was also observed in separate analyses of patients naïve to furosemide and those chronically exposed to furosemide. Regardless of these patterns, naïve to furosemide individuals excreted more ions (both uCl- and uNa+) than chronically exposed patients at all timepoints. Additionally, a strong, linear correlation between uCl- and uNa+ was observed in each post-furosemide timepoint (the strongest in 1 h r = 0.87; P < 0.001). Both interdependent ions concentration was almost parallel when analysed in chronic furosemide users and those naïve to furosemide separately [uCl- = 0.85 * uNa+ + 28.82, P < 0.001, R2 = 0.83 for chronic furosemide users, and uCl- = 0.72 * uNa+ + 41.55, P < 0.001, R2 = 0.65 for naïves to furosemide (linear regression model)]. Moreover, uCl- (with cutoff point: 72 mmol/L) was a satisfactory predictive factor for poor diuretic response (<100 mL/h in 6 h since the beginning of furosemide infusion) [odds ratio (OR) 95% confidence interval (CI): 39.0 (3.8-405.00)]. It presented those properties also after adjusting for urine creatinine [cutoff point: 0.296 mmol/mg-OR (95% CI): 81.0 (8.0-816.0)].

CONCLUSIONS

Urine chloride and sodium are highly interrelated during decongestion of AHF patients. The uCl- (cutoff 72 mmol/L) exhibits better prognostic abilities to identify poor diuretic response than uNa+.

Evaluation of the Accuracy of Point-of-Care Urine Chloride Measured via Strip Test in Patients with Heart Failure

BACKGROUND

In clinical practice, patient self-monitoring is crucial in achieving therapeutic goals in various diseases. In heart failure (HF), it is particularly important due to the increasing role of urine composition. Therefore, we proposed this study to assess the accuracy of urine chloride (uCl-) assessment via strip test in relation to chloride and sodium (uNa+) measurements in a gold-standard laboratory method.

METHODS

Urine samples were collected before administering morning medications. Afterwards, they were analyzed concurrently using the strip test and gold-standard laboratory method.

RESULTS

The study cohort comprised 66 patients (82% male, mean age 68 ± 12 years), of whom 65% were diagnosed with HF and 35% without HF. Across the entire cohort, a strong correlation was observed between uCl- measured by both methods (r = 0.85; p < 0.001). However, the strip test was found to underestimate uCl- relative to the laboratory measurements (mean difference of 18 mmol/L). Furthermore, strong correlations were observed between the methods among patients with HF and without HF (r = 0.88 vs. r = 0.71, respectively; p < 0.001 for both), where they presented similar relationship patterns. Interestingly, in patients with a low glomerular filtration rate (eGFR ≤ 60 mL/min/1.73 m2), the correlation between both methods was greater compared to those with high eGFR (>60 mL/min/1.73 m2) (r = 0.94 vs. r = 0.76, respectively; p < 0.001 for both). The relationship between uCl- from the strip test and uNa+ from the laboratory measurement was weaker than for uCl-, but it was significant.

CONCLUSIONS

These findings suggest that point-of-care strip tests for assessing urinary chloride demonstrate high accuracy and potential utility, particularly in patients with reduced eGFR.