Search PubMed⌕ Search

Biomedical subjects

T Kouri

Publications and source records attributed to T Kouri.

At least 19 recordsLinked to original sources
PubMed2005

Pre-analytical factors and measurement uncertainty.

Pre-analytical factors are an important source of variation or errors in clinical laboratory measurements. Based on the new accreditation standards, medical and laboratory professions now seek to develop tools to deal systematically with these diverse factors. Several obvious pre-analytical uncertainty components were estimated in pragmatic experiments and combined with data on analytical variation and literature knowledge on biological variation, to estimate the measurement uncertainty of most common chemical and haematological examinations in clinical laboratories. The main aim was to assess quality specifications for regional laboratory services. The expanded measurement uncertainties (level of confidence 95%) of serum cholesterol, albumin and potassium remained within 13-16%. The major uncertainty component for cholesterol was biological variation, whereas those for albumin and potassium were sample collection and pretreatment. The measurement uncertainties for serum free thyroxin, thyrotropin and C-reactive protein, 20%, 42% and 125% respectively, were largely due to their biological variation. The measurement uncertainties of basic erythrocyte parameters (erythrocyte count and mean corpuscular volume, blood haemoglobin concentration) were less than 10%. Larger measurement uncertainties were obtained for thrombocyte and leukocyte counts, 24 and 31%, respectively, and for the reticulocyte fraction, 41%.

Adult↗
PubMed2001

Reference intervals for the markers of proteinuria with a standardised bed-rest collection of urine.

Reference intervals for markers of proteinuria or glomerular charge selectivity were measured in 61 healthy female and 61 healthy male individuals. Timed bed-rest and daytime collections were used to assess significance of preanalytical variability of results. Bed-rest collections are advisable for research on renal damage, whereas in routine care, robust protein/creatinine ratios work as practical estimates of protein excretion rates, the correlations to excretion rates improving with increasing proteinuria. For glomerular charge selectivity, pancreatic/salivary isoamylase clearance ratio showed lower within-subject biological variation than IgG/IgG4 clearance ratio, allowing more accurate classification into normal and reduced charge selectivity. With our method, the lower 2.5% reference intervals for isoamylase clearance ratio were 1.1 in men and 1.9 in women.

Acetylglucosaminidase↗
PubMed2000

Reference intervals for cystatin C in pre- and full-term infants and children.

Cystatin C is a non-glycated, 13-kDa basic protein produced by all nucleated cells. Recent studies have indicated that the plasma concentration of cystatin C is a better marker for glomerular filtration rate (GFR) than plasma creatinine, which is most commonly used for this purpose. We established reference values for plasma cystatin C in pre- or full-term infants and children. For comparison we also measured the creatinine concentration in the same samples. Cystatin C was measured by a commercially available immunoturbidimetric method with a Hitachi 704 analyzer in sera obtained from 58 pre-term infants, 50 full-term infants and 299 older children (132 girls, 167 boys, median age 4.17 years, range 8 days to 16 years). No sex differences were found. The pre-term infants had higher cystatin C concentrations (mean 1.88 mg/l, SD 0.36 mg/l) than the full-term (mean 1.70 mg/l, SD 0.26 mg/l, P=0.0145). The reference interval for pre-term infants calculated non-parametrically was 1.34-2.57 mg/l and for full-term infants 1.36-2.23 mg/l. The cystatin C concentration decreased rapidly after birth, and above 3 years of age did not depend on age. The reference interval for children 3-16 years of age calculated non-parametrically was 0.51-1.31 mg/l. Younger children (<1 year: 0.75-1.87 mg/l; 1-3 years: 0.68-1.60 mg/l) had slightly, but significantly, higher plasma cystatin C levels.

Adolescent↗
PubMed2000

Renal function and blood pressure five years after puumala virus-induced nephropathy.

BACKGROUND: Nephropathia epidemica (NE) is a mild form of hemorrhagic fever with renal syndrome caused by Puumala hantavirus. Its long-term prognosis is considered favorable. Some reports suggest, however, that a previous hantavirus infection increases the risk of hypertension. METHODS: We studied 46 previously healthy subjects (26 males and 20 females, mean age of 44 years) who had serologically confirmed NE three to seven years previously, and 38 healthy, seronegative controls (22 males and 16 females, mean age of 44 years). Ambulatory blood pressure (ABP) was monitored. Glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) were determined by 51CrEDTA and 131I-hippurate clearances, respectively. The filtration fraction (FF) was calculated. Quantitative 24-hour urinary protein excretion (UprotE) and timed overnight urinary excretion of alpha1-microglobulin were measured. RESULTS: The NE patients had a higher mean ambulatory systolic BP than the controls (123 +/- 13 vs. 117 +/- 9 mm Hg, P = 0. 008). GFR and FF were increased in patients compared with controls (GFR, 120 +/- 20 vs. 109 +/- 14 mL/min/1.73 m2, P = 0.006; FF, 19 +/- 3 vs. 18 +/- 3%, P = 0.030), but ERPF did not differ between the groups. The patients also had higher UPE than the controls (median 0. 18 g/day, range 0.12 to 0.38 vs. median 0.14 g/day, range 0.09 to 0. 24, P < 0.001, respectively). The overnight urinary excretion rate of alpha1-microglobulin exceeded 7 microg/min in nine patients. CONCLUSION: Three to seven years after NE, the patients had higher GFR and FF, more proteinuria, and higher ambulatory systolic BP compared with the healthy controls. NE may thus cause mild renal lesions and alterations in BP in some patients.

Acute Kidney Injury↗
PubMed2000

External quality assessment of urine analysis in Europe. Results of a round table discussion during the symposium 'From uroscopy to molecular analysis', Seeon, Germany, September 18-20, 1999.

Interlaboratory surveys on urine quantities have only recently been introduced in several European countries. Representatives of 10 European countries exchanged their experiences during an international urinalysis meeting held in September 1999. Although still not mandatory in most areas, more than 5000 laboratories participated in external quality assessment programs in the countries represented. Qualitative (test strips and microscopic morphology) as well as quantitative chemical and immunochemical quantities were included. The maximal allowable deviations are reported as well as methods used to determine target values. Consensus scales up to reference methods were applied. The participants agreed that quality criteria need to be defined separate from those already existing for plasma/serum analytes. Besides higher biological variables and different medical needs, less standardisation of methods to quantify urine constituents was observed as a major cause of higher interlaboratory differences.

Europe↗
PubMed2000

Bone isoenzyme of serum alkaline phosphatase and serum inorganic phosphate in metabolic bone disease of prematurity.

UNLABELLED: We wanted to improve detection of low bone mineral density in preterm infants by combining serum measurements of total alkaline phosphatase, its bone-type isoenzyme and serum inorganic phosphate in a prospective design. The subjects were 43 preterm infants. Total and bone isoenzyme activity of alkaline phosphatase was determined at 3 wk chronological age and at 3 and 6 mo corrected age. The main outcome measure, apparent bone mineral density (BMAD) at the distal forearm and forearm shaft, was assessed by dual energy X-ray absorptiometry at 3 and 6 mo corrected age. An apparent density below 95 mg/cm3 at 3 mo corrected age was considered to indicate bone disease, based on the distribution of BMAD values of children with non-complicated courses of prematurity. At 3 mo corrected age, total alkaline phosphatase activities exceeding 900 IU/l revealed low bone mineral density with 88% sensitivity and 71% specificity. Measurements of bone isoenzyme activity did not improve diagnostic performance. Serum inorganic phosphate levels below 1.8 mmol/l reflected low bone density with high specificity (96%), but the sensitivity was only 50%. CONCLUSION: A combination of the criteria "serum total alkaline phosphatase activity above 900 IU/l" and "serum inorganic phosphate concentrations below 1.8 mmol/l" yielded a sensitivity of 100% at a specificity of 70%. This was the best available screening method for low bone mineral density in preterms.

Absorptiometry, Photon↗
PubMed1999

Quality specifications for ordinal scale measurements with multiproperty (multiple) urine test strips.

Analytical quality specifications for ordinal scale measurements have not been presented so far. Criteria are suggested for multiproperty (multiple) urine test strips based on upper limits of healthy reference intervals, analytical performance and statistical tests applicable to ordinal scales. Trueness (accuracy) can be evaluated against an acceptable comparison method by applying sensitivity and specificity concepts, and defining a grey zone with a lower detection limit and an upper confirmation limit. Concordance (agreement) of two or more ordinal scale categories should be evaluated by subtracting random agreement, using Kappa statistics. Repeatability (precision) can be calculated for categorized results using binomial statistics.

Clinical Laboratory Techniques↗
PubMed1999

The occurrence of renal involvement in primary Sjögren's syndrome: a study of 78 patients.

OBJECTIVE: To ascertain the occurrence of renal involvement in patients with primary Sjögren's syndrome (pSS). METHODS: Urinary total protein excretion from 24 h urine collection, as well as urinary excretion rates of albumin, alpha-1 microglobulin (alpha1m) and IgG from overnight 8 h collections, were determined from 78 pSS patients (75 females, three males). Urine acidification capacity after oral ammonium chloride load was tested in 55 of these patients. RESULTS: Mild proteinuria (0.15-0.42 g/24 h) was observed in 34 patients (44%). Increased urinary excretion rates of albumin (>/=20 microgram/min), alpha1m (>/=7.0 microgram/min) or IgG (>/=5.0 microgram/min) were detected in nine (12%), nine (12%) and 11 patients (14%), respectively. Latent or overt distal renal tubular acidosis (dRTA) was observed in 18 out of 55 patients with pSS (33%). These patients had a longer duration of the disease (10+/-4 vs 8+/-4 yr; P</=0.05); they also had proteinuria (67 vs 27%; P</=0.025) and hypertension (44 vs 14%; P</=0.05) more frequently, and significantly higher serum creatinine (92+/-39 vs 78+/-13 micromol/l; P</=0.025) and serum beta-2 microglobulin (beta2m) levels (3.3+/-1.6 g/l vs 2.6+/-0. 6 g/l; P</=0.025) as compared to patients with normal urine acidification capacity. CONCLUSIONS: Inadequate renal acidification capacity, as well as mild proteinuria, were frequently found in patients with pSS. Those with dRTA had longer disease duration, a higher level of serum beta2m, and they had proteinuria and hypertension more frequently than those with normal renal acidification capacity.

Acidosis, Renal Tubular↗
PubMed1999

Randomised controlled trial of vitamin D supplementation on bone density and biochemical indices in preterm infants.

AIMS: To test the hypothesis that a vitamin D dose of 200 IU/kg, maximum 400 IU/day, given to preterm infants will maintain normal vitamin D status and will result in as high a bone mineral density as that attained with the recommended dose of 960 IU/day. METHODS: Thirty nine infants of fewer than 33 weeks of gestational age were randomly allocated to receive vitamin D 200 IU/kg of body weight/day up to a maximum of 400 IU/day or 960 IU/day until 3 months old. Vitamin D metabolites, bone mineral content and density were determined by dual energy x-ray absorptiometry, and plasma ionised calcium, plasma alkaline phosphatase, and intact parahormone measurements were used to evaluate outcomes. RESULTS: The 25 hydroxy vitamin D concentrations tended to be higher in infants receiving 960 IU/day, but the differences did not reach significance at any age. There was no difference between the infants receiving low or high vitamin D dose in bone mineral content nor in bone mineral density at 3 and 6 months corrected age, even after taking potential risk factors into account. CONCLUSIONS: A vitamin D dose of 200 IU/kg of body weight/day up to a maximum of 400 IU/day maintains normal vitamin D status and as good a bone mineral accretion as the previously recommended higher dose of 960 IU/day. Vitamin D is a potent hormone which affects organs other than bone and should not be given in excess to preterm infants.

25-Hydroxyvitamin D 2↗
PubMed1998

Immune responses and clinical outcome of massive human osteoarticular allografts.

Cell mediated immune responses as measured by lymphocyte proliferation induced by the mitogens phytohemagglutinin and concanavalin A and antigen extracts of donor derived bone were studied within 2 years after wide resection of bone tumors in 18 patients receiving fresh frozen massive osteoarticular allografts. No uniform changes were seen in mitogen induced responses in 18 patients. However, five of nine patients tested with antigen extracts of donor derived bone showed elevated immune responses, one moderate and four weak. The incorporation of the allograft (evaluated by repeated radiographs; specific isotope techniques; clinical outcome assessed by the functional rating scores of Mankin-Waber and the Musculoskeletal Tumor Society; and histologic biopsy findings on new bone formation) did not differ in these patients from those in patients without any response to donor derived tissue. During a long term followup (mean, 11 years; range, 2-20 years), degenerative joint and sclerotic density bone changes developed after 2 to 4 years without correlation to immune responses. Histologic specimens showed no signs of immunologic reaction, and no clinical rejection episodes were recorded. A slightly variable immune response to allograft bone seems to occur, but its clinical significance for outcome of the grafts remains to be determined. The low immune responses might reflect a low antigen release rate through an indirect pathway or immunologic tolerance to antigens or proteins shed from massive allografts that are nonliving scaffold implants during the creeping substitution process, corresponding to the low immune response and the slow histologic repair.

Adolescent↗
PubMed1997

Multicentre evaluation of the urine analyser Miditron Junior.

A multicentre evaluation of the urine analyser Miditron Junior was performed at four laboratories. The Miditron Junior analyser provides semi-quantitative results for erythrocytes, bilirubin, urobilinogen, ketone bodies, glucose, protein, nitrite, leukocytes, pH and relative density. Accuracy of the Miditron Junior analyser was evaluated by comparison to quantitative analytical chemistry methods (glucose, total protein), physical methods (pH, relative density), and microscopic methods (erythrocytes, leukocytes). Agreement was defined as identical or neighbouring concentration block. The level of agreement found with chemical, physical or microscopic methods for the six analytes tested varied from 79 to 99%. The within-run precision was determined as repeatability by using 31 native urines. The results of repeated measurements (n = 10) fell in the same concentration block, or in case of borderline concentration were spaced between two adjacent colour blocks. Day-to-day precision covering a minimum of 20 days using commercially available control solutions yielded results within +/- one colour block from the mean.

Colorimetry↗
PubMed1995

Estimation of reference change limits using patient data.

Two approaches for deriving reference change limits from patient data are described. In the direct method, hospital database information is used for the selection of appropriate reference groups. If database information is not sufficient or reliable enough, but still most of the source data can be considered as health-related, an indirect method can be applied in the calculation of rough estimates for reference change limits. A computer program developed by us, GraphROC for Windows, includes both methods for the estimation of change limits from patient data. Time between specimen collections should be included as one classifying factor in the selection of source data. When only one previous result is available for comparison, change limits based on the reference sample group form the only available guide for clinical interpretation. However, when several previous results are available and the within-subject variances for the considered analyte are known to be heterogeneous between individuals, the clinical interpretation should rather be based on application of time series analysis.

Data Interpretation, Statistical↗
PubMed1995

Reliability and adequacy of discharge diagnosis databases in the production of reference values.

Discharge diagnoses provide a possibility to select patients individually and then to establish reference values for both "pathological" and control groups. Currently, the available diagnostic information is still at its infancy and should be carefully evaluated before the reference values based on those groups are utilized. It is anticipated that electronic storage of diagnostic and therapeutic information will be applied more commonly in the future as the development of computers makes it easier. The advanced utilization of laboratory data challenges physicians both in the clinical and laboratory side to participate in this development in order to make the information systems serve their actual needs more closely.

Clinical Laboratory Information Systems↗
PubMed1994

Reference intervals developed from data for hospitalized patients: computerized method based on combination of laboratory and diagnostic data.

We utilized the databases of a hospital information system to select for determination of reference values various individual hospitalized patients on the basis of their diagnoses at discharge. The nonparametric 2.5-97.5% "health-related" reference intervals were calculated for hemoglobin concentration, mean corpuscular volume (MCV), and erythrocyte count for both sexes. After excluding patients with diseases possibly affecting erythrocyte variables, we obtained a final group of 1786 women and 1450 men, ages 20-65 years, who were studied in age groups of 20-30, 30-45, 45-55, and 55-65 years. The upper reference limits of the MCV results obtained from hospitalized patients were higher than those produced conventionally from healthy individuals, as would be intuitively suggested by clinical experience. This method, based on selection by diagnosis, could be applicable to various analytes measured in hospital laboratories, provided sufficient data are available as databases.

Adult↗
PubMed1994

Performance of NycoCard:::U-Albumin and Micral-Test rapid methods for detecting microalbuminuria.

NycoCard:::U-Albumin and Micral-Test semiquantitative methods were evaluated against nephelometric measurements of nightly albumin excretion rates from 159 consecutive diabetic patients. Both methods can be safely applied for screening of intact renal function even at a strict prediction limit for incipient nephropathy of albumin excretion rate = 15 micrograms/min (standardised specimens collected at bed-rest), since the predictive values of negative tests were 95-100% for both tests. Predictive values of positive tests were 38% (NycoCard:::U-Albumin) and 44% (Micral-Test), if the designated value of 10 mg/l was used as the limit of positivity. By using 20 mg/l as the limit, the predictive values of positive tests were 62% (NycoCard:::U-Albumin) and 72% (Micral-Test), indicating the need for quantitative measurements in patients with positive screening results at both these limits.

Albuminuria↗
PubMed1992

Quality control of multichannel hematology analyzers. Bivariate on-line comparison of MCV and MCH values for the detection of random errors.

Volume and hemoglobin content of red blood cells are physiologically interdependent variables but are measured independently in multichannel hematologic analyzers. Therefore correlation of these results to each other can be used as an additional step in internal quality control. To facilitate precise correlation, data were collected from 44,873 consecutive routine determinations of red blood cell parameters. Gaussian distributions were fitted to the original distributions and bivariate elliptical acceptance limits were calculated for simultaneous evaluation of mean corpuscular volume and mean corpuscular hemoglobin results. With the proposed method, rare combinations of the three directly measured red blood cell parameters (hemoglobin, red blood cell count, and mean corpuscular volume) can be identified for the detection of random analytical or preanalytical errors. This mean corpuscular volume-mean corpuscular hemoglobin rule could be added to internal quality-control programs of hematologic analyzers to improve detection of unusual results and possible random errors.

Diagnosis, Computer-Assisted↗