Plasma uric acid and plasma albumin in healthy subjects

Uric acid is a useful marker to differentiate between responsive and refractory status epilepticus

OBJECTIVES

Early recognition of refractory status epilepticus (RSE) is essential to select an appropriate treatment strategy and is closely associated with the outcome. Only few studies of RSE biomarkers exist; hence, we investigated the serum levels of uric acid (UA), albumin, and C-reactive protein (CRP) as potential serologic biomarkers for RSE.

PATIENTS AND METHODS

Consecutive status epilepticus (SE) patients who had serial conventional blood tests in a referral hospital over a period of 10 years were retrospectively analyzed. Patients with anoxic encephalopathy, renal failure, acute stroke, and myocardial infarction were excluded. RSE was defined as seizure continuing after the first- and second-line treatments. We also assessed SE severity in all included patients using the Status Epilepticus Severity Score (STESS). General demographics and blood test findings were compared between responsive SE and RSE patients.

RESULTS

A total of 141 patients (99 responsive and 42 refractory) were recruited from our SE registry. Compared to responsive patients, patients with RSE showed a higher STESS, lower initial albumin levels, lower initial UA levels, lower follow-up UA levels, and greater reduction of UA levels. The RSE group more frequently had acute symptomatic etiology, showed longer hospitalization, and had poorer functional outcomes compared to the responsive-SE group. All evaluated UA level parameters exhibited significant areas under the curve in receiver operating characteristic analyses, predictive of RSE. Initial UA levels, as well as changes therein, were significantly associated with RSE in multivariate logistic regression analysis.

CONCLUSION

UA levels at initial and follow-up evaluations, and changes therein differentiated responsive SE and RSE, demonstrating the feasibility of UA serum levels as a biomarker for RSE.

Reference distributions for the negative acute-phase proteins, albumin, transferrin, and transthyretin: a comparison of a large cohort to the world's literature

Clinical interpretation of the acute-phase proteins--albumin, transferrin, and transthyretin--has been hampered by the lack of accurate and precise methods for quantifying the levels and a stable and respected reference material. Now that these issues have been addressed, the community is faced with the need for credible age- and gender-specific reference values. The number of publications that address this issue, even for an analyte as familiar as albumin, is small and, in most cases, such publications lack the relevant data that would allow a combined experience to be created. We have identified 40 studies that meet our criteria: a description of the study participants' health status, of the statistical methodology, and of the laboratory technique and/or reference material used. Few of these studies reported values stratified by gender. A summary of the published median levels by age is presented for the three analytes, along with our own age- and gender-specific medians based on a large cohort. Ten of the studies presented a 95 percent reference range, in close agreement with ours where selection was based upon reported diagnosis rather than upon determination of individual health status. This meta-analysis provides support for the reliability of our recently published methodology and reference data for the clinical interpretation of individual albumin, transferrin, and transthyretin values. As with most laboratory measurements, clinical interpretation requires that other laboratory and clinical factors be considered.

Protein binding of aspirin and salicylate measured by in vivo ultrafiltration

OBJECTIVE

Methods for measuring protein binding of drugs generally require direct measurement of the concentration of unbound drug and thus may require a highly sensitive assay. In vivo ultrafiltration has been used to determine protein binding of endogenous substances. We have examined its value for measuring protein binding of drugs because it requires measurement of only the concentration of total drug, not unbound drug, in plasma.

METHODS

The protein binding of aspirin and its metabolite salicylate was measured in 29 healthy subjects 20 minutes after a single oral dose of 600 mg soluble aspirin, by the new method, in vivo ultrafiltration, as well as by a standard method, in vitro ultracentrifugation.

RESULTS

The data for salicylate were examined systematically to determine the optimal method of determining estimates of protein binding by in vivo ultrafiltration. Estimates of protein binding of salicylate were 81.7% +/- 10.1% (mean +/- SD) by the in vivo method and 81.6% +/- 11.3% by in vitro ultracentrifugation. Bland-Altman analysis of agreement showed that within-individual differences in percentage of protein binding determined by the two methods did not differ significantly from zero (mean difference, 0.07%; 95% confidence interval, -2.33 to +2.46). There was a highly significant correlation between estimates of protein binding by the two methods (r = 0.82; p = 0.001). Protein binding of aspirin was estimated of protein binding by the two methods (r = 0.82; p = 0.001). Protein binding of aspirin was estimated at 58.3% +/- 9.6% by in vivo ultrafiltration and could not be estimated by in vitro ultracentrifugation because the concentration of unbound aspirin in plasma was below the limit of detection for the assay.

CONCLUSION

In vivo ultrafiltration can be used to measure protein binding of drugs and has potential advantages over conventional methods. A sensitive assay may not be required because the unbound drug need not be measured, measurement in vivo may maintain more physiologic conditions, and it may be useful in measuring protein binding of drugs that are degraded rapidly in vitro.