Age- and gender-specific reference values of estimated GFR in Caucasians: the Nijmegen Biomedical Study.

The Nijmegen Biomedical Study is a population-based cross-sectional study conducted in the eastern part of the Netherlands. As part of the overall study, we provide reference values of estimated glomerular filtration rate (GFR) for this Caucasian population without expressed risk. Age-stratified, randomly selected inhabitants received a postal questionnaire on lifestyle and medical history. In a large subset of the responders, serum creatinine was measured. The GFR was then measured using the abbreviated Modification of Diet in Renal Disease (MDRD) formula. To limit possible bias, serum creatinine was calibrated against measurements performed in the original MDRD laboratory. The study cohort included 2823 male and 3274 female Caucasian persons aged 18-90 years. A reference population of apparently healthy subjects was selected by excluding persons with known hypertension, diabetes, cardiovascular- or renal diseases. This healthy study cohort included 1660 male subjects and 2072 female subjects, of which 869 of both genders were 65 years or older. The median GFR was 85 ml/min/1.73 m(2) in 30-to 34-year-old men and 83 ml/min/1.73 m(2) in similar aged women. In these healthy persons, GFR declined approximately 0.4 ml/min/year. Our study provides age- and gender-specific reference values of GFR in a population of Caucasian persons without identifiable risk.

Adsorption of erythropoietin and growth hormone to peritoneal dialysis bags and tubing.

OBJECTIVE: To study the adsorption of erythropoietin and growth hormone to dialysis bags and tubing. DESIGN: In vitro study in which radiolabeled erythropoietin and recombinant human growth hormone were added to small-volume (50- and 250-mL) dialysis bags. Recovery was measured after 15-minute dwells. Experiments were performed in triplicate. SETTING: University hospital. RESULTS: Adsorption of erythropoietin and growth hormone was less than 7%. CONCLUSION: Adsorption of erythropoietin and recombinant human growth hormone to dialysis bags and tubing is minimal. This finding provides another argument in favor of intraperitoneal therapy in pediatric peritoneal dialysis.

Quantitative measurement of telomerase reverse transcriptase (hTERT) mRNA in urothelial cell carcinomas.

Telomerase reverse transcriptase (hTERT) messenger RNA has been detected in 95% of bladder tumors using RT-PCR. In this study, we quantified the expression of hTERT in 35 bladder urothelial cell carcinomas and in 6 normal bladder epithelia using a real-time quantitative PCR assay. hTERT expression was detected in all 35 urothelial cell carcinomas of varying grade and stage, but not in normal tissue samples. An increase in both pathological grade and clinical stage as prognostic parameters correlated with increased hTERT expression. Using different cutoff values for grades and stages, normalized hTERT expression values could discriminate among low, medium, and high grade tumors and between superficial and muscle-invasive tumors. We conclude that standardized real-time measurement of hTERT expression can be used for early tumor detection and may be used for determination of prognosis in urothelial cell carcinomas of the bladder.

A model for harmonization of routine clinical chemistry results between clinical laboratories.

Clinical chemistry laboratory results from different laboratories often show large between-laboratory variation due to factors such as differences in method principles, method applications, calibration procedures or the application of different instrument factor settings within the same calibration procedure. We have examined the possible use of common calibrators to reduce this variation. Three different calibrators were compared: A, freeze-dried preparations of pooled patients' serum samples, spiked to give three concentration levels; B, freeze-dried preparations of pooled patients' serum samples selected on the basis of elevated enzyme activities at three levels; C, a single calibrator consisting of frozen pooled serum samples. These calibrators were sent to 11 participating laboratories together with 14 fresh patients' serum samples. We report the variation of the results of 21 general clinical chemistry analytes obtained in the patients' serum samples before and after recalculation on the basis of the results of the calibrators. For most analytes the use of a multiple point linear regression calibration function is able to reduce the between-laboratory variation considerably from more than 30% (enzymes) to values well within the bias limits set by European quality specifications, when the necessary conditions are met. These conditions include the commutability of the calibrator(s) with fresh patients' material. For the enzymes, calibrator material originating from selectively pooled patients' samples appeared to be necessary, whereas for the substrates selectively pooled serum calibrators spiked with exogenous supplements may be used. For harmonization to be effective in practice, calibrators need to be stable over time and to carry assigned values set by certified reference laboratories, and the quality performance of participating laboratories should be appropriately monitored.

Real-time quantification of human telomerase reverse transcriptase mRNA in tumors and healthy tissues.

BACKGROUND: Expression of the hTERT gene, which codes for the catalytic subunit of telomerase, is associated with malignancy. We recently developed a real-time reverse transcription-PCR assay, based on TaqMan technology, for accurate and reproducible determination of hTERT mRNA expression (Lab Investig 1999;79:911-2). This method may be of interest for molecular tumor diagnostics in tissues and corresponding body fluids, washings, or brushes. METHODS: In this study, we measured hTERT expression in a subset of healthy tissues and tumors to select those tumor types with the best potential for quantification of hTERT in corresponding body fluids. To demonstrate the use of the method in body fluids, we quantified hTERT expression in voided urine of patients with bladder cancer and controls. RESULTS: Real-time measurement of hTERT expression could discriminate between all healthy and malignant tissue samples from pancreas, lung, esophagus, and bladder, but not for colon tissues. Moreover, in five of nine (55%) urine samples, hTERT could be quantified. CONCLUSIONS: The present study demonstrates that accurate quantitative measurement of hTERT expression has high potential for discrimination between healthy and tumor cells in tissues and urine and supports future measurements in pancreatic fluid, bronchoalveolar lavage fluid, esophageal brushings, and urine or bladder washings.

Follow-up study of peritoneal fluid kinetics in infants and children on peritoneal dialysis.

OBJECTIVES: To study longitudinal changes in transcapillary ultrafiltration (TCUF) and marker clearance (MC), as a reflection of lymphatic absorption, in children on peritoneal dialysis (PD). To present data on fluid kinetics in infants younger than 2.5 years, using an intraperitoneal volume of 1200 mL/m2 body surface area (BSA). DESIGN: The study involved a 4-hour dwell of 1200 mL/m2 BSA of dialysis fluid containing 3.86% glucose with Dextran 70 as volume marker. Cumulative TCUF and cumulative MC were measured. SETTING: A tertiary-care university hospital. PATIENTS: A follow-up period of 33 months of serial (1 - 4) peritoneal equilibration tests (PETs) was studied in 20 children with a median age of 6.4 years (range 2.1 - 15.4 years). Fluid kinetics in 5 additional infants with a median age of 1.4 years (range 0.5 - 2.5 years) was measured. RESULTS: Cumulative TCUF was 1041 mL/1.73 m2 at 1 - 3 months after start of PD, 1026 mL/1.73 m2 at 7 - 9 months, 1021 mL/1.73 m2 at 11 - 13 months, and 756 mL/1.73 m2 at 26 - 33 months (NS). Cumulative MC was 235 mL/1.73 m2 at 1 - 3 months after start of PD, 311 mL/1.73 m2 at 7 - 9 months, 395 mL/1.73 m2 at 11 - 13 months, and 509 mL/1.73 m2 at 26 - 33 months (NS). In infants, cumulative TCUF was 755 +/- 237 mL/1.73 m2; cumulative MC was 400 +/- 214 mL/1.73 m2. CONCLUSIONS: Transcapillary ultrafiltration and marker clearance do not change in children > 2.5 years during the period studied. Fluid kinetics does not differ between infants < 2.5 years and older children when intraperitoneal volumes of 1200 mL/m2 BSA are used.

Effect of intraduodenal bile salt on pancreaticobiliary responses to bombesin and to cholecystokinin in humans.

Bile salts modulate postprandial gallbladder emptying and pancreatic enzyme secretion, possibly by interfering with plasma cholecystokinin (CCK) responses. The regulatory role of bile salts in the absence of nutrients from the gut is poorly understood. Therefore, we studied the effect of intraduodenal sodium chenodeoxycholate on bombesin (BBS)- or CCK-stimulated plasma CCK levels, plasma pancreatic polypeptide levels, gallbladder motility, and pancreatic enzyme secretion. In a crossover design, saline without or with chenodeoxycholate was perfused intraduodenally for 3 hours in healthy volunteers. During the last hour, either BBS (n = 9) or CCK (n = 10) was infused intravenously. Chenodeoxycholate inhibited BBS-stimulated gallbladder emptying from 59% +/- 4% to 34% +/- 6% (P <.05) and intraduodenal bilirubin output from 41 +/- 9 to 21 +/- 5 micromol/h (P <.05), but it increased integrated plasma CCK levels from 157 +/- 19 to 184 +/- 19 pmol/L. 60 min (P =.01). Similarly, chenodeoxycholate administration inhibited gallbladder emptying and bilirubin output in response to intravenous CCK. Chenodeoxycholate also tended to reduce pancreatic polypeptide release and intraduodenal amylase output in response to intravenous BBS or CCK. It is concluded that intraduodenal chenodeoxycholate administration inhibits BBS- or CCK-stimulated gallbladder emptying, probably by diminishing target organ sensitivity to circulating CCK.

Peritoneal protein loss in children with nephrotic syndrome during peritoneal dialysis.

BACKGROUND: The passage of proteins across the glomerular filtration barrier is mainly determined by the size of the protein. In nephrotic syndrome (NS) the glomerular permselectivity is affected, causing proteinuria. Some authors suggest the existence of a generalized basement membrane defect. The permeability characteristics of the peritoneal basement membrane in children with NS are not known. METHODS: The transperitoneal transport of proteins with a different molecular weight (beta2-microglobulin MW 11800 D, albumin MW 69000 D, IgG MW 160000 D, and alpha2-macroglobulin MW 820000 D) was studied in a study group (group A) consisting of six stable nephrotic children (three with glomerulosclerosis and three with congenital nephrotic syndrome, one of them with mesangial sclerosis) and compared to a control group (group B) consisting of eight stable children on peritoneal dialysis. After a dwell of 6 h with Dianeal 1.36% dialysate and serum samples were collected. For each patient the dialysate to plasma (D/P) ratios of the four proteins were calculated. The D/P ratios of the nephrotic patients in group A were compared to the D/P ratios of the patients in the control group B. Data were expressed as mean +/- SD. RESULTS: The values for the D/P ratios (in percentage) of beta2-microglobulin, albumin, IgG and alpha2-macroglobulin in group A were 19.6+/-9.9, 2.7+/-1.7, 1.6+/-0.9, and 0.5+/-0.4, compared to 24.9+/-10.2, 4.0+/-2.3, 2.2 +/- 1.2, and 0.7 +/- 0.3 in the control group B. The ratios were plotted against MW on a double logarithmic scale. In all patients a linear relationship between molecular weight and D/P ratio of the proteins was obtained. The D/P ratios of the study group did not differ significantly from the control group. CONCLUSION: We conclude that the size selectivity of the capillary permeability is not affected in the peritoneal membrane in children with NS due to glomerulosclerosis and congenital nephrotic syndrome.

Inhibition of pancreaticobiliary secretion by loperamide in humans.

Loperamide, a peripherally acting opiate receptor agonist with antidiarrheal action, inhibits ileal and colonic motor function. It was determined whether loperamide also affects gallbladder emptying and pancreatic enzyme secretion in humans. Plasma cholecystokinin (radioimmunoassay), gallbladder volume (ultrasonography), and intraduodenal bilirubin and amylase output (spot sampling) were measured at regular intervals before and during intraduodenal perfusion of an amino acid meal in 8 healthy subjects: once without and once with pretreatment of 8 mg loperamide, ingested 13 and 4 hours before the start of the meal. Loperamide decreased basal amylase output from 3.2 +/- 0.5 to 1.0 +/- 0.5 kU/h (P < .005) and abolished basal bilirubin output (21 +/- 5 vs. 0 +/- 0 micromol/h; P < .005) into the duodenum. Loperamide increased basal gallbladder volume from 28 +/- 4 to 39 +/- 4 mL (P < .0001) but was without effect on basal plasma cholecystokinin (2.7 +/- 0.3 vs. 3.0 +/- 0.3 pmol/L). During the amino acid meal, pretreatment with loperamide inhibited amylase output from 5.1 +/- 0.8 to 1.6 +/- 0.4 kU/h (P < .001), bilirubin output from 39 +/- 6 to 18 +/- 6 micromol/h (P < .0005) and gallbladder contraction from 47% +/- 3% to 26% +/- 6% (P < .05), whereas loperamide enhanced amino acid-stimulated plasma cholecystokinin from 4.5 +/- 1.6 to 7.6 +/- 1.0 pmol/L (P < .05). It is concluded that loperamide inhibits basal and amino acid-stimulated gallbladder motility and intraduodenal output of bilirubin and amylase, despite an enhanced postprandial cholecystokinin release.

Cholestyramine influences meal-stimulated pancreaticobiliary function and plasma cholecystokinin independent of gastric emptying and food digestion.

BACKGROUND: Cholestyramine enhances gallbladder emptying and plasma cholecystokinin responses to oral ingestion of a mixed meal. It is not known whether this effect occurs independently of alterations in gastric emptying or maldigestion of nutrients. METHODS: We perfused 15 g of an amino acid meal intraduodenally for 60 min in seven healthy volunteers, once with and once without cholestyramine. Intraduodenal perfusion of saline with or without cholestyramine (6 g/h) was started 60 min before the amino acid meal and continued for 2 h. RESULTS: Cholestyramine markedly enhanced the incremental plasma cholecystokinin response to the meal from 36 +/- 12 to 139 +/- 25 pmol/l x 60 min (P < 0.005), incremental amylase output from 2.4 +/- 0.7 to 5.7 +/- 0.7 kU/h (P < 0.05), and incremental integrated gallbladder contraction from 1948 +/- 235 to 2840 +/- 189% x 60 min (P < 0.05). CONCLUSION: The enhancing effect of cholestyramine on postprandial gallbladder contraction, pancreatic enzyme secretion, and plasma cholecystokinin release is not dependent on gastric emptying rates or appropriate digestion of nutrients.

Adequate dialysis? Measurement of KT/V in a pediatric peritoneal dialysis population.

OBJECTIVE: To measure the urea and creatinine kinetics in a pediatric population. PATIENTS AND METHODS: In 19 children treated with peritoneal dialysis (PD) KT/V, urea and creatinine clearances (Ccr) were measured. Thirteen children were on continuous ambulatory peritoneal dialysis (CAPD) and 6 on highly intermittent peritoneal dialysis (NIPD). RESULTS: Mean KT/V per week was 2.31 +/- 0.78 and mean creatinine clearance 74 +/- 47 L/week/1.73 m2. There was no difference in dialytic KT/V between patients treated with CAPD and NIPD (1.75 +/- 0.21 vs 1.76 +/- 0.50). The correlation between KT/V urea and creatinine clearance was 0.9 (p < 0.001). There was a clear relationship of these parameters with residual renal function, but not with age or blood urea level. A weak positive correlation was found with serum albumin and protein intake. CONCLUSIONS: Mean KT/V in this patient group was higher than the values reported for most adult patient groups. Residual renal function considerably contributes to this high KT/V. It is not clearly defined which KT/V should be aimed for, since criteria for adequate dialysis are multifactorially determined and therefore difficult to interpret.

The characterisation of leukaemias with the Sysmex NE-8000.

Blood samples from 118 patients with acute and chronic leukaemia and with more than 50% leukaemic cells were processed with the automated haematology analyser Sysmex NE-8000. For 92 out of these 118 the differences in the histograms and scattergrams of the NE-8000 could be used in an attempt to characterise the leukaemia. This interpretation of the histograms and scattergrams appeared to be highly suggestive of the distinction between lymphatic leukaemia and myeloid leukaemia, and could be indicative of the presence of either the chronic or acute form of both the lymphatic and myeloid leukaemias.

Role of intraduodenal proteases in plasma cholecystokinin and pancreaticobiliary responses to protein and amino acids.

BACKGROUND & AIMS: The role of small intestinal proteolytic activity in the regulation of upper gastrointestinal function in humans is poorly understood. The aim of this study was to determine the importance of proteolytic activity for protein- or amino acid-induced cholecystokinin release and pancreaticobiliary secretion. METHODS: In 9 healthy subjects, saline was perfused intraduodenally for 3 hours either with or without the synthetic protease inhibitor camostate. During the last hour, albumin or amino acids in the same molecular composition as albumin were also perfused. RESULTS: Perfusion with camostate, in concentrations that abolished intraduodenal proteolytic activity, had no effect on unstimulated plasma cholecystokinin concentrations or gallbladder emptying, but markedly (P < 0.05) increased unstimulated pancreatic enzyme output. Perfusion with protein distinctly stimulated cholecystokinin release, gallbladder emptying, and pancreatic enzyme output (P < 0.05). Perfusion with camostate resulted in significantly lower protein-stimulated plasma cholecystokinin, gallbladder, and pancreatic enzyme responses (P < 0.05). Perfusion with amino acids also stimulated plasma cholecystokinin, gallbladder emptying, and pancreatic enzyme output (P < 0.05). Camostate did not inhibit these values. CONCLUSIONS: This study shows that appropriate digestion of protein is required to stimulate plasma cholecystokinin release, gallbladder emptying, and pancreatic enzyme secretion in humans.

Testing the accuracy of total cholesterol assays in an external quality-control program. Effect of adding sucrose to lyophilized control sera compared with use of fresh or frozen sera.

We studied the suitability of various types of human serum preparations to test the accuracy of total cholesterol measurements in the External Quality Assessment scheme in The Netherlands, in which approximately 180 laboratories participate. Checked against the certified Abell/Kendall Reference Method, large reagent-dependent negative biases were observed with lyophilized serum that was insufficiently cryoprotected. The biases for the reagents of Du Pont, Roche, and Beckman averaged -16.7%, -9.2%, and -7.6% respectively; the least bias, -0.4%, was obtained with reagent from Boehringer Mannheim. The beneficial effect of cryoprotection with sucrose was demonstrated by the decrease in interreagent variation from 5.4% to 1.9%, the latter value being comparable with the values for fresh and once-frozen pooled serum (1.3% and 1.7%, respectively). We conclude that the detrimental effect of lyophilization on serum matrix can be minimized by suitable cryoprotection with 200 g/L sucrose.