Anion gap reference intervals show instrument dependence and weak correlation with albumin levels

Inpatient diabetes management

Diabetes mellitus is currently approaching epidemic proportions and disproportionately affects patients in the hospital setting. In the United States, individuals living with diabetes represent over 17 million emergency department visits and 8 million admissions annually. The management of these patients in the hospital setting is complex and differs considerably from the outpatient setting. All patients with hyperglycemia should be screened for diabetes, as in-hospital hyperglycemia portends a greater risk for morbidity, mortality, admission to an intensive care unit, and increased hospital length of stay. However, the definition of hyperglycemia, glycemic targets, and strategies to manage hyperglycemia in the inpatient setting can vary greatly depending on the population considered. Moreover, the presenting illness, changing nutritional status, and concurrent hospital medications often necessitate thoughtful consideration to adjustments of home diabetes regimens and/or the initiation of new insulin doses. This review article will examine core concepts and emerging new literature surrounding inpatient diabetes management, including glycemic targets, insulin dosing strategies, noninsulin medications, new diabetes technologies, inpatient diabetes management teams, and discharge planning strategies, to optimize patient safety and satisfaction, clinical outcomes, and even hospital financial health.

Serum Anion Gap at Admission Predicts All-Cause Mortality in Critically Ill Patients With Cirrhosis: A Retrospective Cohort Study

INTRODUCTION

The primary objective of this study was to evaluate admission serum anion gap (AG) as a predictor of all-cause mortality in critically ill patients with cirrhosis.

METHODS

A total of 3,084 cirrhotic patients were included and randomly divided into training and validation cohorts (n = 2,159 and 925, respectively). Patients were categorized into high and normal AG groups based on their AG values. Cox regression and Kaplan-Meier survival analysis were used to assess the relationships between AG levels and outcomes.

RESULTS

Both cohorts showed strong parameter similarity ( P > 0.05). High AG was associated with significantly lower survival probabilities. Cox models confirmed elevated AG as a risk factor, even after adjusting for covariates (hazard ratio: 1.920, 1.793, and 1.764 for 30-day, 60-day, and hospital mortality, respectively). Subgroup analyses, especially regarding chronic kidney disease, revealed complex interactions. Serum AG displayed predictive power comparable with established scoring systems.

DISCUSSION

Elevated AG at admission is a valuable predictor of poor outcomes and increased mortality risk in critically ill cirrhotic patients. Serum AG can serve as an easily accessible tool for risk assessment and prognosis evaluation in this population.

New solutions to old problems: A practical approach to identify samples with intravenous fluid contamination in clinical laboratories

OBJECTIVES

Contamination with intravenous (IV) fluids is a common cause of specimen rejection or erroneous results in hospitalized patients. Identification of contaminated samples can be difficult. Common measures such as failed delta checks may not be adequately sensitive nor specific. This study aimed to determine detection criteria using commonly ordered tests to identify IV fluid contamination and validate the use of these criteria.

METHODS

Confirmed contaminated and non-contaminated samples were used to identify patterns in laboratory results to develop criteria to detect IV fluid contamination. The proposed criteria were implemented at a tertiary care hospital laboratory to assess performance prospectively for 6 months, and applied to retrospective chemistry results from 3 hospitals and 1 community lab to determine feasibility and flagging rates. The algorithm was also tested at an external institution for transferability.

RESULTS

The proposed algorithm had a positive predictive value of 92 %, negative predictive value of 91 % and overall agreement of 92 % when two or more criteria are met (n = 214). The flagging rates were 0.03 % to 0.07 % for hospital and 0.003 % for community laboratories.

CONCLUSIONS

The proposed algorithm identified true contamination with low false flagging rates in tertiary care urban hospital laboratories. Retrospective and prospective analysis suggest the algorithm is suitable for implementation in clinical laboratories to identify samples with possible IV fluid contamination for further investigation.

Dynamics of serum anion gaps with in-hospital mortality: Analysis of the multi-open databases

BACKGROUND

Few studies have investigated the relationship between the anion gap, including the corrected anion gap, and patient mortality in intensive care units (ICUs) without restricting the analysis to specific diseases or medical specialties. Our primary objective was to investigate the association between the anion gap and ICU mortality using multiple open-access databases.

METHODS

We identified 4229 subjects from the Medical Information Mart for Intensive Care IV (MIMIC-IV) database, whose entries were from between 2008 and 2019. For each patient, the anion gap and corrected anion gap were calculated, and the study sample was divided into tertile groups (T) according to these levels. The association between the anion gap and in-hospital mortality was assessed using hazard ratios (HRs) and 95% confidence intervals (CIs) derived from a multivariable-adjusted Cox proportional hazards model. Besides MIMIC-IV, we also incorporated study samples from two other databases (MIMIC-III and electronic ICU) to calculate summary HRs using a random-effects meta-analysis.

RESULTS

Within MIMIC-IV, 1015 patients (24%) died during an average follow-up period of 15.5 days. The fully adjusted HRs and 95% CIs for T2 and T3, relative to T1, were 1.31 (95% CI 1.08-1.58) and 1.54 (95% CI 1.24-1.90), respectively. When grouped by corrected anion gap, the results remained statistically significant. In the meta-analysis, the summary HRs and 95% CIs for T2 and T3 were 1.24 (95% CI 1.08-1.43) and 1.55 (95% CI 1.33-1.82), respectively.

CONCLUSIONS

Both the anion gap and corrected anion gap were associated with in-hospital mortality regardless of specific diseases or medical specialties.

Association between albumin-corrected anion gap level and the risk of acute kidney injury in intensive care unit

PURPOSE

This study was to investigate the association between albumin-corrected anion gap (AG) (ACAG) levels and the risk of acute kidney injury (AKI) in intensive care unit (ICU) patients.

METHODS

The ICU patients of this retrospective cohort study were collected from the Medical Information Mart for Intensive Care IV (MIMIC-IV) database between 2008 and 2019. ACAG = AG + {4.4 - [albumin (g/dl)]} × 2.5. The incidence of AKI was determined using the Kidney Disease: Improving Global Outcomes (KDIGO) definition. The logistic regression model was used to evaluate the association between ACAG levels and the risk of AKI. Subgroup analyses were applied based on age, gender, mechanical ventilation, vasopressors, the Charlson comorbidity index (CCI), and the Simplified Acute Physiology Score II (SAPS II).

RESULTS

Totally, 5586 patients were enrolled, of which 1929 patients (34.53%) occurred AKI. The higher levels of ACAG were associated with the risk of AKI in ICU patients, with the odds ratio (OR) value being 1.23 [95% confidence interval (CI): 1.22-1.24, P = 0.005] in ACAG level between 16.5 and 19.5, and OR value being 1.20 (95% CI 1.16-1.24, P = 0.016) in ACAG level > 19.5. A higher ACAG level was associated with a higher risk of AKI in ICU patients aged < 65 years, in ICU patients of female gender, in ICU patients who used mechanical ventilation, in ICU patients who did not use vasopressors, in patients without cardiogenic shock, and in ICU patients with CCI ≥ 2, and SAPS II > 31 (all P < 0.05).

CONCLUSION

There is an association between ACAG level and the risk of AKI in ICU patients. A higher ACAG value in ICU patients should therefore receive more attention.

Association between albumin corrected anion gap and all-cause mortality in critically ill patients with acute kidney injury: a retrospective study based on MIMIC-IV database

BACKGROUND

The early identification of patients at high risk for acute kidney injury (AKI) with a poor prognosis is crucial to prevent complications and minimize mortality. This study sought to investigate the association between albumin-corrected anion gap (ACAG) and all-cause mortality among critically ill patients with AKI.

METHODS

All eligible AKI patients from the Medical Information Mart for Intensive Care IV (MIMIC-IV version 2.0) database were considered for participation in this study. We employed Kaplan-Meier curves to assess the 30-d and 360-d cumulative survival rates among various groups. Flexibly visualizing the connection between ACAG and mortality, we utilize restricted cubic splines (RCS) and multivariate Cox regression models. Result robustness underwent assessment through subgroup analyses and sensitivity analyses. Receiver-operating characteristic (ROC) curves were generated to evaluate the predictive performance of ACAG.

RESULTS

The study included 9625 AKI participants, of whom 58.60% were male, and the 360-d all-cause mortality rate was 39.89%. According to Kaplan-Meier analysis, the 30-d and 360-d cumulative survival rates for AKI patients were significantly lower in the high ACAG group than in the normal ACAG group. RCS analysis indicated that ACAG levels had a non-linear correlation with the risk of 30-d and 360-d mortality for AKI patients. Cox regression analysis demonstrated that ACAG is an independent risk indicator for 30-d and 360-d prognosis in AKI patients in the ICU.

CONCLUSIONS

Elevated ACAG levels (> 20 mmol/L) at ICU admission were associated with 30-d and 360-d all-cause mortality in critically ill patients with AKI.

Association between serum anion gap and all-cause mortality in patients with acute myocardial infarction: A retrospective study based on MIMIC-IV database

Background

Although previous studies have reported that many biomarkers can determine the prognosis of patients with acute myocardial infarction (AMI), serum anion gap (AG) has not been well studied. We aimed to investigate the association between serum AG and mortality in patients with AMI.

Methods

Adult patients first admitted to the ICU and diagnosed with AMI from 2008 to 2019 in the MIMIC-IV database were included. Patients were divided into the survival and non-survival groups based on 30-day and 90-day outcomes. According to the AG value (15.12 mmol/L) with a hazard ratio of 1 in the restricted cubic spline (RCS) analysis, patients were further divided into high and low AG groups. The Kaplan-Meier survival curve was plotted, and all-cause mortality was compared between the high and low groups using the log-rank test. Multivariate Cox regression analysis and RCS analysis were constructed to assess the relationship between AG and recent all-cause mortality in patients with AMI.

Results

4446 patients were enrolled. The 30-day and 90-day mortality rates in the high AG group (25.53%, 31.75%) were higher than that in the low AG group (9.73%, 14.01%, P < 0.001) independently. The Kaplan-Meier curve showed that the 30-day and 90-day cumulative survival rates were lower in the high AG group than that in the low AG group (P < 0.001). RCS analysis showed that there was a non-linear relationship between AG and the risk of 90-day all-cause mortality in patients with AMI (χ2 = 18.680 P < 0.001). When AG was 15.12 mmol/L, its HR was about 1. Multivariable Cox regression analysis confirmed that increased AG was associated with higher 30-day and 90-day mortality.

Conclusion

Elevated serum AG (≥15.12 mmol/L) is an independent predictor for short-term mortality in patients with AMI, and it may provide a basis for clinicians to identify patients with poor prognosis as early as possible.

The association between albumin corrected anion gap and ICU mortality in acute kidney injury patients requiring continuous renal replacement therapy

The relationship between albumin corrected anion gap (ACAG) and mortality in acute kidney injury (AKI) patients who received continuous renal replacement therapy (CRRT) has not been investigated in any previous studies. This study aimed to investigate the relationship between ACAG at CRRT initiation and all-cause mortality among these patients in the intensive care unit (ICU). Patients diagnosed with AKI and treated with CRRT in the ICU from the Medical Information Mart for Intensive Care-IV version 1.0 (MIMIC IV) database and Huzhou Central Hospital were retrospectively enrolled. Participants were divided into two groups: the normal ACAG group (12-20 mmol/L) and high ACAG group (> 20 mmol/L). The Kaplan-Meier method and log-rank test were used to compare the survival rate between the two groups. Restricted cubic spine (RCS) and Cox proportional-hazards models were utilized to analyze the relationship between ACAG at CRRT initiation and ICU all-cause mortality of these patients. A total of 708 patients met the inclusion criteria in the study. The all-cause mortality of these patients during ICU hospitalization was 41.95%. Patients in the high ACAG group exhibited significantly higher ICU all-cause mortality rate than patients in the normal ACAG group (all P < 0.001). The Kaplan-Meier survival curves showed that the normal ACAG group had a higher ICU cumulative survival rate than the high ACAG group (log-rank test, χ₁²= 13.620, χ₂² = 12.460, both P < 0.001). In the multivariate COX regression analyses, patients with higher ACAG (> 20 mmol/L) levels at the time of CRRT initiation in the MIMIC IV database and Huzhou Central Hospital were significantly correlated with ICU all-cause mortality after adjusting multiple potential confounding factors with hazard ratios of 2.852 (95% CI 1.718-4.734) and 2.637(95% CI 1.584-4.389), respectively. In critically AKI patients who undergo CRRT, higher ACAG (> 20 mmol/L) level at the initiation of CRRT was significantly correlated with ICU all-cause mortality. Therefore, clinicians should pay more attention to those patients with a higher ACAG value.

Methanol poisoning in the emergency department: a retrospective study

Aim: Massive methanol poisonings have occurred in the past decades, resulting in a large number of deaths. In this study, our aim is to retrospectively analyze methanol poisoning cases admitted to the emergency department between 2019-2021, to evaluate their demographic characteristics, causes of poisoning, clinical and laboratory findings, treatments applied and mortality, and to contribute to the poisoning data of our country. Material and Method: The cases of methanol poisoning who applied to the emergency department in a 3-year period were analyzed retrospectively. Medical files of patients aged 18 years and older were reviewed. Patients diagnosed with 'methanol poisoning' as a result of the examination were included in the study. Results: A total of 59 patients were included in the study. 88% (n=52) of the patients with a mean age of 53±10 were male. The presence of neurological symptoms and GCS were associated with mortality among the symptoms of patients presenting to the emergency department (p=0.017, p

Anion gap physiology and faults of the correction formula

DISCLAIMER

In an effort to expedite the publication of articles, AJHP is posting manuscripts online as soon as possible after acceptance. Accepted manuscripts have been peer-reviewed and copyedited, but are posted online before technical formatting and author proofing. These manuscripts are not the final version of record and will be replaced with the final article (formatted per AJHP style and proofed by the authors) at a later time.

PURPOSE

The anion gap is a calculated fundamental laboratory parameter used to identify and monitor acid-base disturbances. A recently popularized correction formula transforms the resulting integer to compensate for hypoalbuminemia and improve diagnostic yield. Clinical pharmacists should be aware of the underlying biochemistry, interpretation, and limitations of this formula to discern drug- and disease-related etiologies.

SUMMARY

The anion gap is utilized in most care settings, ranging from outpatient monitoring to inpatient intensive care units. Supported by decades of experience, the original anion gap derives its value from its simplicity. Applying the anion gap in metabolic acidosis can help narrow differential diagnosis and detect concomitant acid-base disorders. To account for hypoalbuminemia and potential missed diagnoses, a correction formula was developed to improve sensitivity. Yet, the law of electroneutrality ensures that hypoalbuminemia is already accounted for in the original anion gap, and the proposed correction formula was derived from samples unrepresentative of human physiology. Evidence from clinical trials shows no benefit from applying the correction formula.

CONCLUSION

There is no advantage to correcting the anion gap, and such correction may increase the risk of misinterpretation or error. Clinicians should understand these limitations when diagnosing or trending acid-base disturbances.

The Serum Anion Gap Revisited: A Verified Reference Interval for Contemporary Use

BACKGROUND

The anion gap (AG) is often used to evaluate acid-base disorders. The reference interval for normal AG is used to differentiate between raised (gap) or normal AG (non-gap) acidosis. Historically accepted AG values may not be valid with the evolution of modern analytical techniques and the reference interval requires revalidation.

AIMS

To determine the reference interval for AG based on current laboratory techniques.

METHODS

During a health-screening exercise, 284 participants with no major illnesses volunteered surplus blood for analysis. The samples were tested in an internationally-accredited clinical laboratory. AG was calculated by (Na⁺ ) - (Cl^- ) - (HCO3^- ) and AG_K by (Na⁺ ) + (K⁺ ) - (Cl^- ) - (HCO₃ ^- ). The reference interval was determined at 2.5th-97.5th percentiles. Analysis was further undertaken for a sub-cohort of 156 individuals with no sub-optimal health indicators.

RESULTS

Median age was 35 years, BMI 23.4 kg/m² and glomerular filtration rate 106 mL/min/1.73m² . Median AG was 13 mmol/L and the reference interval for normal AG is 10-18 mmol/L with a 99% level of confidence. Statistically significant differences in AG were detected for sex, race, obesity and serum albumin but the difference was 1 mmol/L between subgroups. The reference interval was the same for the sub-cohort of 156 individuals. Median AG_K was 17.7 mmol/L and reference interval was 14.6-22.5 mmol/L.

CONCLUSIONS

The AG reference interval of 10-18 mmol/L is valid for laboratories with similar reference intervals for electrolytes. Lower values expected with current laboratory techniques were not observed. The median AG of 13 mmol/L may be used to differentiate gap acidosis, non-gap acidosis or mixed acid-base disorders. This article is protected by copyright. All rights reserved.

A Higher Serum Anion Gap Is Associated with the Risk of Progressing to Impaired Fasting Glucose and Diabetes

Impaired fasting glucose (IFG) is a reversible intermediate hyperglycemia stage with an increasing risk of diabetes and related complications. Our study was designed to identify the relationship between the serum anion gap and the risk of progressing to impaired fasting glucose and diabetes. Here, we performed a prospective, population-based study among 1191 Chinese individuals aged 22-87 years who took health examinations annually between 2006 and 2012 including clinical features and plasma metabolites. All of the participants had no history of diabetes or related chronic complications. Logistic regression analysis was designed to examine the associations between clinical and metabolomic factors and the risk of developing IFG or diabetes. Among them, 58 subjects whose fasting glucose were between 6.1 and 7 mmol/L were diagnosed as IFG or diabetes. After adjusting for age, sex, body mass index (BMI), high-density lipoprotein (HDL), low-density lipoprotein (LDL), alanine aminotransferase (ALT), aspartate aminotransferase (AST), systolic blood pressure (SBP), diastolic blood pressure (DBP), potassium, and albumin at baseline, the participants in the upper tertiles of serum anion gap (SAG) had higher odds of progressing to IFG or diabetes than those in the lower tertiles. A receiver operating characteristic (ROC) curve was analyzed, and the optimal cutoff level for the anion gap to predict incident IFG or diabetes was 13.76 mmol/L, and the area under the ROC curve (AUC) was 0.623. Our data demonstrate that a higher serum anion gap is associated with the risk of developing IFG or diabetes.