SUMMARY.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 C,8 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 pmo1/24 h. The range for plasma oxalate concentration is 0.6-2.8 pmol/L or 0.7-3.9 pmol/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.

SUMMARY. The acidification response to NH 4 Clloading (0·1 glkg 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. pl-l, 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 m 2 • 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.

Use of point-of-care testing (POCT) equipment by paramedics for triage may reduce unnecessary attendance in emergency departments and inconvenience to patients. A hospital pathology service and an ambulance trust wanted a system for safe and effective use of diagnostic devices by paramedics at the patient bedside. A suite of POCT devices to perform an expanded repertoire of pathology tests was provided, along with technology for electronic data capture, temperature control and monitoring, in a specially designed kit bag—the Labkit. Following a proof-of-concept phase, three Labkit bags were deployed as a pilot in rapid response vehicles and used by specialist paramedics in urgent and emergency care who had been trained in their use. The paramedics used the bag in 25% of patient interactions, typically three times every 24 hours. Having POCT results available at the time of paramedic assessment reduced conveyance to the emergency department by 21%. There was also a 10% rise in admission of patients where pathology results indicated problems that required urgent treatment which would otherwise have gone unnoticed. Overall, 31% of conveyance decisions were changed as a direct consequence of the Labkit results. Patients reported high levels of satisfaction, and paramedics said it added value in 97% of cases where it was used to support decision-making. Reliable, quality-assured POCT by paramedics has the potential to improve efficiency in the healthcare system and benefit patients.

SUMMARY. 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 970/0 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 JLmol/L) oxalate concentrations and better than CV 7% at higher concentrations (greater than 270 JLmol/L)Urinary oxalate values obtained with the new enzymic procedure correlated more closely with HPLC values (r = O' 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. Additional key phrases: urolithiasis; solid phase extraction; centrifugal analysis; ascorbate interferenceThe importance of urinary oxalate measurement is now well recognized.' Increased urinary oxalate excretion facilitates formation of the sparingly soluble calcium oxalate in the urinary tract, significantly increasing the likelihood of renal stone formation.Elevated urinary oxalate concentrations may result from ingestion of foods rich in oxalate or its precursors, increased formation of oxalate due to primary hyperoxaluria or other inborn errors of metabolism, or increased absorption of oxalate as a consequence of gastrointestinal disease or previous gut surgery.Many methods for analysis of urinary oxalate have been described.v" Of those methods suitable for routine use in clinical chemistry laboratories, an enzymic kit methodology Correspondence: Dr B J Starkey. 186 marketed by Sigma Chemical Co. has found wide acceptance. In its initial form however, the procedure was shown to be prone to significant interference from ascorbic acid." Attempts to erradicate this problem by treatment with ferric chloride, sodium nitrite or ascorbate oxidase met with only partial success.! Other interferences, together with the reported pH-dependence of oxalate recovery? detracted from the quality of performance of the assay. These deficiencies in the method led to the development and marketing of a modified procedure in which pretreatment of diluted urine with activated charcoal was claimed to remove the interferences.We have previously developed a simple, high performance liquid chromatographic assay for urinary oxalate." Initially we studied the comparative analytical performance of this HPLC procedure and the enzymic kit in its original form.

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.

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