The anion gap and routine serum protein measurements in monoclonal gammopathies

Spurious Electrolyte and Acid-Base Disorders in the Patient With Cancer: A Review

Electrolyte and acid-base disorders are frequently encountered in patients with malignancy, either due to cancer itself or as a complication of its therapy. However, spurious electrolyte disorders can complicate the interpretation and management of these patients. Several electrolytes can be artifactually increased or decreased such that the serum electrolyte values do not correspond to their actual systemic levels, potentially resulting in extensive diagnostic investigations and therapeutic interventions. Examples of spurious derangements include pseudohyponatremia, pseudohypokalemia, pseudohyperkalemia, pseudohypophosphatemia, pseudohyperphosphatemia, and artifactual acid-base abnormalities. Correctly interpreting these artifactual laboratory abnormalities is imperative for avoiding unnecessary and potentially harmful interventions in cancer patients. The factors influencing these spurious results also must be recognized, along with the steps to minimize them. We present a narrative review of commonly reported pseudo electrolyte disorders and describe strategies to exclude erroneous interpretations of these laboratory values and avoid pitfalls. Awareness and recognition of spurious electrolyte and acid-base disorders can prevent unnecessary and harmful treatments.

From Toxic Ingestion to Cancer: Dramatic Acidosis as a Myeloma-Defining Event

Acute kidney failure has myriad causes and presentations. This is a case of an individual with a history of alcohol abuse and a previous suicide attempt presenting with acute kidney failure and altered mentation accompanied by an anion gap metabolic acidosis with an elevated osmolar gap. These findings were concerning for toxic alcohol ingestion, but the patient was ultimately diagnosed with multiple myeloma. This case demonstrates the multiple factors that can impact both the anion and osmolar gaps. It shows that the traditionally held dogma about the meaning of anion or osmolar gaps may cloud an otherwise more obscure etiology. It illustrates a dramatic presentation of acute myeloma, for which early recognition is essential to initiate appropriate chemotherapy for a chance at preservation of renal function.

Serum Levels of Interleukin-1β and Disease Progression in Multiple Myeloma Patients: A Case and Control Study

OBJECTIVE

Multiple myeloma  (MM) is known as an incurable heterogeneous plasma cell malignancy that presents with a variety of clinical manifestations. Inflammation plays an important role in this disease. Cytokines and Chemokines cause the progression of the disease. One of them is interleukin-1β (IL-1β), which may be involved in the pathogenesis of MM. Other markers such as calcium, albumin, creatinine, globulins, and total protein are also used to diagnose and prognosis patients. The main purpose of this study was to evaluate the serum level of IL-1β and various forms of calcium (total calcium, ionized calcium, and corrected calcium), albumin, creatinine, globulin, and total protein on stage-I of MM patients and healthy controls.

METHODS

Serum samples from 30 stage-I MM patients and 30 healthy subjects as controls were examined in this study. The protein concentrations of serum IL-1β was assessed by enzyme-linked immunosorbent assay (ELISA), total calcium, albumin, creatinine, total protein, and globulin Measured by auto analyzer BT3000, an electrolyte analyzer was used to measure ionized calcium (Ca++) and a special equation was used to calculate the corrected calcium.

RESULT

The mean level of IL-1β was significantly elevated in stage-I MM. The mean levels of IL-1β were 7.04±1.15 ng/ml in stage-I MM and 3.12± 0.90 ng/ml in controls (p<0.001). The mean levels of total calcium (total Ca) were 9.45±0.56 mg/dl in stage-I MM and 9.09±0.43mg/dl in controls (p=0.008). The mean levels of ionized calcium (Ca++) was 4.65±0.28mg/dl in stage-I MM and 4.75±0.33mg/dl in controls (p=0.2). The mean ratio of serum ionized calcium to total calcium (Ca++/ total Ca) was 0.49±0.054 in stage-I MM and 0.52±0.047 in controls (p=0.02). The mean ratio of serum ionized calcium to corrected calcium (Ca++/corrected Ca) was 0.42±0.033 in stage-I MM and the Mean ratio of serum ionized calcium to calcium total (Ca++/ total Ca) was 0.52±0.047 in controls, Comparison of the mean of the two groups shows a significant difference (p<0.001). The mean level of albumin was 1.72±0.35 g/dl in stage-I MM and4.32±0.41g/dl in controls (p<0.001). The mean level of total protein was 12.65±0.81g/dl in stage-I MM and 7.07±0.4 g/dl in controls (p<0.001). The mean level of globulin was 11.00±0.96 mg/dl in stage-I MM and 2.85±0.77 mg/dl in controls (p<0.001). The mean level of creatinine was 1.15±0.25 mg/dl in stage-I MM and 0.96±0.15 mg/dl in controls (p=0.001).

CONCLUSION

The results of the study indicate the possible involvement of IL-1β at stage-I MM and it can indicate the role of chemokines in the disease process, especially in the early stages. Changes in the chemical profiles mentioned can help in the diagnosis and prognosis of the disease.

Increased plasma and brain immunoglobulin A in Alzheimer’s disease is lost in apolipoprotein E ε4 carriers

Background

Alzheimer’s disease (AD) is foremost characterized by β-amyloid (Aβ)-extracellular plaques, tau-intraneuronal fibrillary tangles (NFT), and neuroinflammation, but over the last years it has become evident that peripheral inflammation might also contribute to the disease. AD patients often demonstrate increased levels of circulating proinflammatory mediators and altered antibody levels in the blood. In our study, we investigated the plasma Immunoglobulin A (IgA) levels in association with apolipoprotein E (APOE) ε4 status and Aβ pathology.

Methods

IgA levels in antemortem-collected (cohort I) and postmortem-collected (cohort II) plasma samples from AD patients (n = 30 in cohort I and n = 16 in cohort II) and non-demented age-matched controls (NC) (n = 42 in cohort I and n = 7 in cohort II) were measured using ELISA. Hippocampal sections from cohort II were immunostained against IgA, and the IgA area fraction as well as the number of IgA positive (IgA+) cells in the cornu ammonis region were analysed using ImageJ. The relationship between plasma IgA levels and cognition, C-reactive protein (CRP), and cerebrospinal fluid (CSF) AD biomarkers in cohort I as well as neuropathology, IgA+ cell number, and IgA area fraction in cohort II was analysed before and after grouping the cohorts into APOEε4 carriers and APOEε4 non-carriers.

Results

Plasma IgA levels were higher in AD patients compared to NC in both cohorts. Also, AD patients demonstrated higher IgA area fraction and IgA+ cell number compared to NC. When APOEε4 status was considered, higher plasma IgA levels in AD patients were only seen in APOEε4 non-carriers. Finally, plasma IgA levels, exclusively in APOEε4 non-carriers, were associated with cognition, CRP, and CSF Aβ levels in cohort I as well as with IgA area fraction, IgA+ cell number, and Aβ, Lewy body, and NFT neuropathology in cohort II.

Conclusions

Our study suggests that AD pathology and cognitive decline are associated with increased plasma IgA levels in an APOE allele-dependent manner, where the associations are lost in APOEε4 carriers.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13195-022-01062-z.

Association between serum Na-Cl level and renal function decline in chronic kidney disease: results from the chronic kidney disease Japan cohort (CKD-JAC) study

BACKGROUND

Metabolic acidosis, which reduces serum bicarbonate levels, contributes to the progression of chronic kidney disease (CKD). The difference between sodium and chloride (Na-Cl) may theoretically predict serum bicarbonate levels. This study aimed to evaluate serum Na-Cl level as a risk factor for renal function decline among patients who participated in the chronic kidney disease Japan cohort (CKD-JAC) study.

METHODS

The association between low Na-Cl concentration (< 34 mmol/L) and composite renal function decline events (any initiation of renal replacement therapy or 50% decline in estimated glomerular filtration rate) was evaluated among 2143 patients with CKD stage G3a-4. Using Cox regression analysis, hazard ratios (HRs) were estimated after adjusting for the following covariates: age, sex, diabetes mellitus, diabetic nephropathy, cardiovascular disease, anemia, angiotensin-converting enzyme inhibitors and angiotensin II receptor antagonists, loop diuretics, cigarette smoking, body mass index, serum albumin, systolic blood pressure, urine albumin-to-creatinine ratio, and CKD stage.

RESULTS

Composite renal function decline events were observed in 405 patients (18.9%) over the 4-year follow-up period. Low serum Na-Cl level (< 34 mmol/L) was independently associated with a greater risk for composite renal function decline events (HR 1.384; 95% confidence interval [CI], 1.116-1.717). Subgroup analyses identified that the association between low Na-Cl level and composite renal function decline events was stronger among patients with CKD stage G4 and those with anemia.

CONCLUSIONS

Our investigation suggests that Na-Cl is an independent predictor of CKD progression, especially among patients with CKD stage G4 and those with anemia.

Approach to the Patient With a Negative Anion Gap

When anion gap calculation generates a very small or negative number, an explanation must be sought. Sporadic (nonreproducible) measurement errors and systematic (reproducible) laboratory errors must be considered. If an error is ruled out, 2 general possibilities exist. A true anion gap reduction can be generated by either reduced concentrations of unmeasured anions such as albumin or increased concentrations of unmeasured cations such as magnesium, calcium, or lithium. This teaching case describes a patient with aspirin (salicylate) poisoning whose anion gap was markedly reduced (-47 mEq/L). The discussion systematically reviews the possibilities and provides the explanation for this unusual laboratory result.

A survey of preoperative blood tests in primary open-angle glaucoma patients versus cataract surgery patients

PURPOSE

To investigate biomarker differences in routine preoperative blood tests performed on primary open-angle glaucoma (POAG) case and control patients presenting for anterior segment eye surgery.

METHODS

POAG cases and age-related cataract surgery patients (controls) who underwent anterior segment surgery at Massachusetts Eye and Ear from January 2009 through March 2012 were identified by retrospective record review. Patients with diabetes mellitus, secondary glaucoma, and cataract due to trauma or steroid exposure were excluded. Data on demographic features, preoperative ophthalmological and medical diagnosis, blood pressure, anthropometric measures, basic metabolic panel, and complete blood count were extracted from the medical records. Univariate differences in lab values between POAG cases and controls were assessed using unpaired t tests. Multivariate logistic regression analysis was completed to determine the independent associations of biomarkers with POAG.

RESULTS

A total of 150 cases and 150 age-related controls were included. In multivariate analysis, higher AG was inversely associated with POAG (odds ratio [OR] = 0.90; 95% confidence interval [CI], 0.80-1.00), and higher Cl- level was positively associated with POAG (OR = 1.15; 95% CI, 1.02-1.29). The lower AG in POAG patients could be explained by higher IgG levels as the available data in post hoc analysis showed a nonsignificant trend toward higher IgG in cases compared to controls (17 vs 23; 1142 ± 284 mg/dl vs 1028 ± 291 mg/dl; P = 0.22). Furthermore, in multivariable analysis, a higher red blood cell count was also associated with POAG (OR = 1.91; 95% CI, 1.11-3.28).

CONCLUSIONS

Patients with POAG presenting for anterior segment surgery had a lower AG compared to age-related cataract surgery patients. The etiology of this reduced gap is unclear but the possible contribution of IgG warrants further exploration. The etiology of higher red blood cell counts in POAG cases is unknown and deserves further exploration.

The serum anion gap in the evaluation of acid-base disorders: what are its limitations and can its effectiveness be improved?

The serum anion gap has been utilized to identify errors in the measurement of electrolytes, to detect paraproteins, and, most relevant to the nephrologist, to evaluate patients with suspected acid-base disorders. In regard to the latter purpose, traditionally an increased anion gap is identified when it exceeds the upper limit of normal for a particular clinical laboratory measurement. However, because there is a wide range of normal values (often 8-10 mEq/L), an increase in anion concentration can be present in the absence of an increased anion gap. In addition, the type of retained anion can affect the magnitude of the increase in anion gap relative to change in serum [HCO3(-)] being greater with lactic acidosis compared with ketoacidosis. This review examines the methods of calculation of the serum anion gap in textbooks and published literature, the effect of perturbations other than changes in acid-base balance, and its effectiveness in identifying mild and more severe disturbances in acid-base balance. Limitations of the present methods of determining the normal anion gap and change in the anion gap are highlighted. The possibility of identifying the baseline value for individuals to optimize the use of the calculation in the detection of metabolic acidosis is suggested.

Ion-selective electrode and anion gap range: What should the anion gap be?

Background

Using flame photometry technique in the 1970s, the normal value of anion gap (AG) was determined to be 12 ± 4 meq/L. However, with introduction of the autoanalyzers using an ion-selective electrode (ISE), the anion gap value has fallen to lower levels.

Methods

A retrospective study of US veterans from a single medical center was performed to determine the value of the anion gap in subjects with normal renal function and normal serum albumin and in patients with lactic acidosis and end-stage renal disease on dialysis.

Results

In 409 patients with an estimated glomerular filtration rate ≥60 mL/min/1.73 m² body surface area and serum albumin ≥4 g/dL, the mean AG was 7.2 ± 2 (range 3–11) meq/L. In 299 patients with lactic acidosis (lactate level ≥4 meq/L) and 68 patients with endstage renal disease on dialysis, the mean AG was 12.5 meq/L and 12.4 meq/L, respectively. A value <2 meq/L should be considered a low anion gap and a possible clue to drug intoxication and paraproteinemic disorders.

Conclusion

With the advent of ISE for measurement of analytes, the value of the anion gap has fallen. Physicians need to be aware of the normal AG value in their respective institutions, and laboratories need to have an established value for AG based on the type of instrument they are using.