Adjusted Anion Gap Is Associated with Glomerular Filtration Rate Decline in Chronic Kidney Disease

Relationship Between Albumin-Corrected Anion Gap and Mortality in Hospitalized Heart Failure Patients

BACKGROUND

Heart failure (HF) is a disease with high morbidity and mortality. Despite the efforts to reduce mortality rates through medical progress, it is necessary to develop markers to identify critically ill patients. In our study, we aimed to investigate the relationship between albumin-corrected anion gap (ACAG) and mortality in hospitalized patients with HF.

METHODOLOGY

We performed a retrospective study that included patients with HF hospitalized in the Erzurum City Hospital between 2015 and 2022. The basal clinical, hematological, and biochemical findings of the patients were obtained from the electronic medical records. ACAG was calculated. The date and causes of death of the patients were searched and recorded through the Republic of Türkiye Ministry of Health Death Notification System (ÖBYS) and Central Population Administration System (MERNIS). Thus, the relationship between ACAG and mortality in hospitalized patients with HF was evaluated.

RESULTS

A total of 205 patients hospitalized for HF were included in the study. The mean age of all people in this study was 71.8 ± 10.7 years. A total of 104 (50.7%) of the patients included in the study were women. The mean left ventricular ejection fraction was 47.2 ± 13.6%. The mean follow-up period of the entire population was 76.5 ± 18.9 months. The mortality rate was 11.7% (24 patients). Serum anion gap (SAG) and ACAG were significantly higher in the group with death outcomes (p = 0.043 and p = 0.012, respectively). Cox regression analysis showed that ACAG was an independent predictor of HF mortality (p = 0.003). ACAG area under the curve was 0.773 (95% CI 0.634 - 0.914), the cut-off was 13, sensitivity was 75%, and specificity was 75.9% (p = 0.002).

CONCLUSION

Statistical analysis showed a meaningful connection between an increase in ACAG and mortality in hospitalized patients with HF. Consequently, ACAG can be used as an independent predictor of mortality in patients with HF.

False-negative diagnosis of high anion gap in patients with end-stage kidney disease

The traditional anion gap (AG) equation is widely used, but its misdiagnosis in end-stage kidney disease (ESKD) patients has not been investigated fully. Diagnostic accuracy to detect high AG was cross-sectionally evaluated using 3 AG equations in 1733 ESKD patients with an eGFR less than 15 mL/min/1.73 m². The prevalence of high AG was 67.9%, 92.1% and 97.4% by the traditional, albumin-adjusted AG (aAG) and full AG equations, respectively. The sensitivity, specificity, accuracy and Kappa coefficient obtained with the traditional AG vs aAG equation were 0.70 vs 0.94, 0.98 vs 0.93, 0.7 vs 0.94, and 0.103 vs 0.44, respectively. Next, we created a subcohort comprising only patients with high full AG and investigated how the traditional AG equation leads to misdiagnoses. Multivariable-adjusted regression analysis in 1688 patients revealed that independent factors associated with a false-negative AG diagnosis were ARB use, eGFR, blood leukocyte count, serum chloride, bicarbonate, ionized calcium, potassium, albumin and phosphate. 93.2% of our subcohort prescribed any of RAAS inhibitors, Loop diuretics or Alkali which could increase either serum chloride or bicarbonate. Frequent use of these possible AG-reducing medications may conceal high AG state in patients with ESKD unless they have incidental inflammation which may increase AG value.

Anion gap predicts early mortality after starting hemodialysis in the elderly

BACKGROUND

Serum anion gap (AG) has recently been proven to represent a biomarker for predicting prognosis in patients with end-stage renal disease (ESRD). However, whether change in AG (ΔAG) at the time of starting hemodialysis predicts mortality after starting hemodialysis in elderly patients with ESRD remains unknown.

METHODS

This retrospective cohort investigated the association between ΔAG and mortality after starting hemodialysis in the elderly. The cohort comprised patients ≥ 75 years old who started hemodialysis for ESRD at National Center for Global Health and Medicine between 2010 and 2017 and at Yokosuka Kyosai Hospital between 2007 and 2011. Patients were stratified into three groups (G1-3) based on ΔAG, calculated according to the equation: ΔAG = sodium - (chloride + bicarbonate) - 12. The primary outcome was death within 1 year of starting hemodialysis. Data were analyzed using Cox proportional hazard models with adjustments for baseline characteristics.

RESULTS

We enrolled 254 patients (59% male). Median ΔAG was 2.6 (G1: > 3, n = 111; G2: 0-3, n = 103; G3: < 0, n = 40). The primary outcome was observed in 43 patients. Hazard ratios (HRs) were significantly higher for G1 and G3 than for G2 (G1: HR 2.47, 95% confidence interval 1.13-5.37; G3: HR 3.86, 95% confidence interval 1.62-9.16). Adjusted HRs (aHRs) were significantly higher for G1 and G3 than for G2 (G1: aHR 3.06, 95% confidence interval 1.23-7.62; G3: aHR 3.12, 95% confidence interval 1.10-8.78).

CONCLUSIONS

A J-curve phenomenon is evident between ΔAG and early mortality after starting hemodialysis in the elderly.

Serum Anion Gap Predicts All-Cause Mortality in Patients with Advanced Chronic Kidney Disease: A Retrospective Analysis of a Randomized Controlled Study

Background and Objectives

Cardiovascular outcomes and mortality rates are poor in advanced chronic kidney disease (CKD) patients. Novel risk factors related to clinical outcomes should be identified.

Methods

A retrospective analysis of data from a randomized controlled study was performed in 440 CKD patients aged > 18 years, with estimated glomerular filtration rate 15–60 mL/min/1.73m². Clinical data were available, and the albumin-adjusted serum anion gap (A-SAG) could be calculated. The outcome analyzed was all-cause mortality.

Results

Of 440 participants, the median (interquartile range, IQR) follow-up duration was 5.1 (3.0–5.5) years. During the follow-up duration, 29 participants died (all-cause mortality 6.6%). The area under the receiver operating characteristic curve of A-SAG for all-cause mortality was 0.616 (95% CI 0.520–0.712, P = 0.037). The best threshold of A-SAG for all-cause mortality was 9.48 mmol/L, with sensitivity 0.793 and specificity 0.431. After adjusting for confounders, A-SAG above 9.48 mmol/L was independently associated with increased risk of all-cause mortality, with hazard ratio 2.968 (95% CI 1.143–7.708, P = 0.025). In our study, serum levels of beta-2 microglobulin and blood urea nitrogen (BUN) were positively associated with A-SAG.

Conclusions

A-SAG is an independent risk factor for all-cause mortality in advanced CKD patients. The positive correlation between A-SAG and serum beta-2 microglobulin or BUN might be a potential reason. Future study is needed.

Trial Registration

Clinicaltrials.gov NCT 00860431