False-positive Troponin I Assay elevation due to occult Mixed Cryoglobulinemic Vasculitis

A 53-year-old man with active hepatitis C and cirrhosis presented with a vasculitic rash, myalgias, and fatigue, and was found to have an elevated cardiac troponin I up to 15.7 ng/mL with normal electrocardiogram, echocardiogram, and coronary angiogram prior to being discharged. Subsequently, during a similar presentation to another academically affiliated hospital, the patient had a normal cardiac troponin T (< 0.01 ng/mL). Upon his third presentation with significantly elevated troponin I to 15.98 ng/mL, the patient was found to have cryoglobulinemic vasculitis and elevated rheumatoid factor due to active hepatitis C, causing interference with the troponin I immunoassay. In conclusion, troponin I assays may have high false-positive values due to interference by rheumatoid factor and/or a polyclonal antibody found in cryoglobulinemia.

Patients,' Nephrologists,' and Predicted Estimations of ESKD Risk Compared with 2-Year Incidence of ESKD

BACKGROUND AND OBJECTIVES

The rate of progression to ESKD is variable, and prognostic information helps patients and physicians plan for future ESKD. We assessed the estimations of ESKD risk of patients with CKD and physicians and compared them with risk calculators and outcomes at 2 years.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This prospective observational study assessed 257 adult patients with CKD stages 3-5 and their nephrologists at University of California, San Diego and Veterans Affairs San Diego CKD clinics. Patients' and nephrologists' estimations of 2-year ESKD risk were evaluated, and objective estimation of 2-year risk was determined using kidney failure risk equations; actual incidence rates of ESKD and death were ascertained by chart review. Participants' baseline characteristics were compared across kidney failure risk equation risk levels and according to whether patients' estimations were more optimistic or pessimistic than physicians' estimations. We examined correlations between estimations and compared estimations with outcomes using c statistics and calibration plots.

RESULTS

Average age was 65 (±13) years old, and eGFR was 34 (±13) ml/min per 1.73 m². Overall, 13% reached ESKD, and 9% died. About one quarter of patients gave estimates that were >20% more optimistic than physicians, and more than one in ten gave estimates that were >20% more pessimistic. Physicians' and kidney failure risk equation estimations had the strongest correlation (r=0.72; P<0.001) compared with 0.50 (P<0.001) between physicians and patients and 0.47 (P<0.001) between patients and kidney failure risk equation. Although all three estimations provided reasonable risk rankings (c statistics >0.8), physicians and patients overestimated risk compared with actual outcomes; no patient whose physician estimated a risk of ESKD <15% reached ESKD at 2 years. The kidney failure risk equation was best calibrated to actual ESKD risk.

CONCLUSIONS

Compared with actual ESKD incidence, the kidney failure risk equation outperformed patients' and physicians' estimations of ESKD incidence. Patients and physicians overestimated risk compared with the kidney failure risk equation.

The Relation of Serum Potassium Concentration with Cardiovascular Events and Mortality in Community-Living Individuals

BACKGROUND AND OBJECTIVES

Hyperkalemia is associated with adverse outcomes in patients with CKD and in hospitalized patients with acute medical conditions. Little is known regarding hyperkalemia, cardiovascular disease (CVD), and mortality in community-living populations. In a pooled analysis of two large observational cohorts, we investigated associations between serum potassium concentrations and CVD events and mortality, and whether potassium-altering medications and eGFR<60 ml/min per 1.73 m2 modified these associations.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Among 9651 individuals from the Multi-Ethnic Study of Atherosclerosis (MESA) and the Cardiovascular Health Study (CHS), who were free of CVD at baseline (2000-2002 in the MESA and 1989-1993 in the CHS), we investigated associations between serum potassium categories (<3.5, 3.5-3.9, 4.0-4.4, 4.5-4.9, and ≥5.0 mEq/L) and CVD events, mortality, and mortality subtypes (CVD versus non-CVD) using Cox proportional hazards models, adjusting for demographics, time-varying eGFR, traditional CVD risk factors, and use of potassium-altering medications.

RESULTS

Compared with serum potassium concentrations between 4.0 and 4.4 mEq/L, those with concentrations ≥5.0 mEq/L were at higher risk for all-cause mortality (hazard ratio, 1.41; 95% confidence interval, 1.12 to 1.76), CVD death (hazard ratio, 1.50; 95% confidence interval, 1.00 to 2.26), and non-CVD death (hazard ratio, 1.40; 95% confidence interval, 1.07 to 1.83) in fully adjusted models. Associations of serum potassium with these end points differed among diuretic users (Pinteraction<0.02 for all), such that participants who had serum potassium ≥5.0 mEq/L and were concurrently using diuretics were at higher risk of each end point compared with those not using diuretics.

CONCLUSIONS

Serum potassium concentration ≥5.0 mEq/L was associated with all-cause mortality, CVD death, and non-CVD death in community-living individuals; associations were stronger in diuretic users. Whether maintenance of potassium within the normal range may improve clinical outcomes requires future study.

Fibroblast Growth Factor-23 and Frailty in Elderly Community-Dwelling Individuals: The Cardiovascular Health Study

OBJECTIVES

To evaluate whether fibroblast growth factor 23 (FGF-23) is related to frailty and to characterize the nature of their joint association with mortality.

DESIGN

Cross-sectional analysis for frailty and longitudinal cohort analysis for mortality.

SETTING

Cardiovascular Health Study.

PARTICIPANTS

Community-dwelling individuals (N = 2,977; mean age 77.9 ± 4.7, 40% male, 83% white).

MEASUREMENTS

The predictor was serum FGF-23 concentration (C-terminal enzyme-linked immunosorbent assay), and the outcomes were frailty status (determined according to frailty phenotype criteria of weight loss, weakness, exhaustion, slowness, and low physical activity) and mortality. Multinomial logistic regression was used to assess the cross-sectional association between FGF-23 and frailty and prefrailty, adjusting for demographic characteristics, cardiovascular disease and risk factors, and kidney markers. Proportional hazards Cox proportional hazards regression was used to assess the association between FGF-23, frailty, and all-cause mortality.

RESULTS

Mean estimated glomerular filtration rate (eGFR) was 64 ± 17 mL/min per 1.73 m(2) . Median FGF-23 was 70.3 RU/mL (interquartile range 53.4-99.2); 52% were prefrail, and 13% were frail. After multivariate adjustment, each doubling in FGF-23 concentration was associated with 38% (95% confidence interval (CI) = 17-62%) higher odds of frailty than of nonfrailty and 16% (95% CI = 3-30%) higher odds of prefrailty. FGF-23 (hazard ratio (HR) = 1.16, 95% CI = 1.10-1.23) and frailty (HR = 1.82, 95% CI = 1.57-2.12) were independently associated with mortality, but neither association was meaningfully attenuated when adjusted for the other.

CONCLUSION

In a large cohort of older adults, higher FGF-23 was independently associated with prevalent frailty and prefrailty. FGF-23 and frailty were independent and additive risk factors for mortality. FGF-23 may be a marker for functional outcomes.

GFR Estimating Equations and Liver Disease

It is important to accurately assess the glomerular filtration rate (GFR) of patients with liver disease to deliver care and allocate organs for transplantation in a way that improves outcomes. The most commonly used methods to estimate GFR in this population are based on creatinine, which is biased by these patients' low creatinine production and potentially by elevated serum bilirubin and decreased albumin levels. None of the creatinine-based estimated glomerular filtration rate (eGFR) equations have been specifically modified for a population with liver disease, and even measurement of a 24-hour creatinine clearance has limitations. In liver disease, all creatinine-based estimates of GFR overestimate gold standard-measured GFR, and the degree of overestimation is highest at lower measured GFR values and in more severe liver disease. Cystatin C-based eGFR has shown promise in general population studies by demonstrating less bias than creatinine-based eGFR and improved association with clinically important outcomes, but results in the liver disease population have been mixed, and further studies are necessary. Ultimately, specific eGFR equations for liver disease or novel methods for estimating GFR may be necessary. However, for now, the limitations of currently available methods need to be appreciated to understand kidney function in liver disease.

Relationship Between 24-Hour Ambulatory Blood Pressure and Cognitive Function in Community-Living Older Adults: The UCSD Ambulatory Blood Pressure Study

BACKGROUND

Twenty-four-hour ambulatory blood pressure (BP) patterns have been associated with diminished cognitive function in hypertensive and very elderly populations. The relationship between ambulatory BP patterns and cognitive function in community-living older adults is unknown.

METHODS

We conducted a cross-sectional study in which 24-hour ambulatory BP, in-clinic BP, and cognitive function measures were obtained from 319 community-living older adults.

RESULTS

The mean age was 72 years, 66% were female, and 13% were African-American. We performed linear regression with performance on the Montreal Cognitive Assessment (MoCA) as the primary outcome and 24-hour BP patterns as the independent variable, adjusting for age, sex, race/ethnicity, education, and comorbidities. Greater nighttime systolic dipping (P = 0.046) and higher 24-hour diastolic BP (DBP; P = 0.015) were both significantly associated with better cognitive function, whereas 24-hour systolic BP (SBP), average real variability, and ambulatory arterial stiffness were not.

CONCLUSIONS

Higher 24-hour DBP and greater nighttime systolic dipping were significantly associated with improved cognitive function. Future studies should examine whether low 24-hour DBP and lack of nighttime systolic dipping predict future cognitive impairment.

GFR Estimating Equations and Liver Disease

It is important to accurately assess the glomerular filtration rate (GFR) of patients with liver disease to deliver care and allocate organs for transplantation in a way that improves outcomes. The most commonly used methods to estimate GFR in this population are based on creatinine, which is biased by these patients' low creatinine production and potentially by elevated serum bilirubin and decreased albumin levels. None of the creatinine-based estimated glomerular filtration rate (eGFR) equations have been specifically modified for a population with liver disease, and even measurement of a 24-hour creatinine clearance has limitations. In liver disease, all creatinine-based estimates of GFR overestimate gold standard-measured GFR, and the degree of overestimation is highest at lower measured GFR values and in more severe liver disease. Cystatin C-based eGFR has shown promise in general population studies by demonstrating less bias than creatinine-based eGFR and improved association with clinically important outcomes, but results in the liver disease population have been mixed, and further studies are necessary. Ultimately, specific eGFR equations for liver disease or novel methods for estimating GFR may be necessary. However, for now, the limitations of currently available methods need to be appreciated to understand kidney function in liver disease.

The Elderly are Different: Initiating Dialysis in Frail Geriatric Patients

Decisions and discussions about the initiation of dialysis in the elderly are often challenging because of the high prevalence of comorbidities and frailty in this population. Mortality is high, functional decline is likely, and quality of life tends to be lower in the elderly on dialysis. It is thus important to counsel these patients on the risks, benefits, and burdens of dialysis to assist them in making an informed choice that is in line with their goals, preferences, and expectations. For some patients, dialysis may be a desirable choice. For others, the alternative of palliative care may provide a more favorable balance of benefits versus burdens. Elderly patients who choose to proceed with dialysis often benefit from an interdisciplinary team that helps to manage and monitor their health status, while maximizing the benefits of treatment and decreasing its potential harms. These goals can be promoted by effective communication and through individualized decisions about vascular access, medication choices, and dietary limitations. Finally, close monitoring of functional status will help to determine whether dialysis remains in a patient's best interest and when alternatives should be offered.