Serum cholesterol concentration before and after streptokinase in acute myocardial infarction.

OBJECTIVE: To determine if serum cholesterol concentration should be measured before or after streptokinase therapy within the first 24 h of myocardial infarction. DESIGN: Prospective study of patients receiving streptokinase therapy for acute myocardial infarction (AMI). SETTING: Coronary care unit of a district general hospital. SUBJECTS: Thirty-one patients (26 men aged 38-74 years, mean 60 years) admitted with a definite diagnosis of myocardial infarction. INTERVENTION: Streptokinase therapy given intravenously at a mean of 5 h (range 1.5-15 h) after the onset of chest pain. MAIN OUTCOME MEASURES: Serum cholesterol concentration just prior to, and 11.5 h (range 4-20.5 h) after streptokinase administration. RESULTS: There was a significant mean fall of 0.4 mmol l-1 (P = 0.002, 95% CI = 0.2-0.6) in serum cholesterol concentration from a pre-streptokinase concentration of 7.0 (range 5.3-9.9) to a post-streptokinase concentration of 6.6 (range 4.9-9.9). In the patients who showed a fall in cholesterol concentration, the magnitude of fall correlated with the baseline cholesterol concentration (r = 0.66, P < 0.01) but not with peak cardiac enzyme activities (r = 0.05, P > 0.2 for aspartate aminotransferase; r = 0.10, P > 0.2 for lactate dehydrogenase), time from onset of chest pain to post-streptokinase measurement (r = 0.27, P > 0.2) or time from streptokinase administration to post-streptokinase measurement (r = 0.01, P > 0.2). CONCLUSION: Serum cholesterol concentration may be underestimated when measured after streptokinase therapy, particularly when the true basal value is high. Further management of this risk factor may be based more accurately on its measurement before than after streptokinase therapy within the first 24 h of AMI.

Comparison of a commercial enzymic kit for urinary oxalate analysis with a high performance liquid chromatographic method.

A new commercial enzymic kit for urinary oxalate determination has been adapted for use on a centrifugal analyser. It has been evaluated and compared with an established high performance liquid chromatographic (HPLC) procedure developed in our laboratory. Mean recovery of oxalate from urine samples augmented with oxalic acid exceeded 97% by both methods. The precision of the HPLC method was superior to that of the enzymic kit but both methods gave between batch precision values better than CV 12% at low (less than 100 mumol/L) oxalate concentrations and better than CV 7% at higher concentrations (greater than 270 mumol/L). Urinary oxalate values obtained with the new enzymic procedure correlated more closely with HPLC values (r = 0.84) than did values previously obtained using the forerunner of the kit (r = 0.62) which was known to be susceptible to ascorbate interference. No significant interference from ascorbic acid or from high urinary calcium concentrations could be demonstrated using either the improved kit or the HPLC procedure. Its easy adaptation to automated analysers available in most laboratories, coupled to its acceptable analytical performance render the enzymic kit a reasonable alternative to HPLC or other more complex procedures for urinary oxalate analysis.

The determination of oxalate in urine and plasma by high performance liquid chromatography.

We describe a simple, sensitive assay for oxalate in urine or plasma. Acidified urine is pretreated by dilution with neutral phosphate buffer and passage through a C18 cartridge. Stabilized plasma is diluted with neutral acetate buffer and oxalate extracted using a strong anion exchange cartridge. Treated samples are applied to an ion-paired chromatographic system and oxalate detected electrochemically. Recovery of oxalate from augmented samples exceeded 97% from both urine and plasma. Within- and between-assay coefficients of variation assessed at three concentrations were, respectively, better than 4.1% and 8.4% for urine and 3.9% and 5.2% for plasma. The reference range for urinary oxalate excretion is 109-497 mumols/24 h. The range for plasma oxalate concentration is 0.6-2.8 mumols/L or 0.7-3.9 mumols/L after an overnight fast or without dietary restriction, respectively. Urine and plasma oxalate concentrations from this method, gave correlation coefficients (r) of 0.97 and 0.98, respectively, when compared with those from established oxalate oxidase based assays.

The acidification response of normal subjects to ammonium chloride using a 3-day loading test.

The acidification response to NH4 Cl loading (0.1 g/kg bw/day) was tested in 16 normal healthy subjects in the basal fasting state on Day 4, the subjects having taken the salt daily for the 3 previous days. The response was measured in terms of blood pH and in urine, creatinine, phosphate, pH, titratable acidity, ammonium, net acidity and creatinine clearance. To minimise inter-subject variation the urine values were adjusted to a standard body surface area of 1.73 m2. A normal range for the blood pH of the mean value +/- 2 SD, encompassed the observed range of values. However, to fit the observed range of acid-base values in urine into the 2 SD range required a logarithmic transformation of the data. Statistical analysis confirmed a significant correlation between blood [H+] net acid secretion, urine titratable acidity and ammonium. Urine net acid secretion was positively correlated with urinary phosphate, titratable acidity and ammonium.