12 research outputs found
Estimation of reference intervals from small samples: an example using canine plasma creatinine
Background: According to international recommendations, reference intervals should be determined from at least 120 reference individuals, which often are impossible to achieve in veterinary clinical pathology, especially
for wild animals. When only a small number of reference subjects is available, the possible bias cannot be known and the normality of the distribution cannot be evaluated. A comparison of reference intervals estimated by different methods could be helpful.
Objective: The purpose of this study was to compare reference limits determined from a large set of canine plasma creatinine reference values, and large subsets of this data, with estimates obtained from small samples selected randomly.
Methods: Twenty sets each of 120 and 27 samples were randomly selected from a set of 1439 plasma creatinine results obtained from healthy dogs in another study. Reference intervals for the whole sample and for the large
samples were determined by a nonparametric method. The estimated reference limits for the small samples were minimum and maximum, mean +/-2 SD of native and BoxâCox-transformed values, 2.5th and 97.5th percentiles by a robust method on native and BoxâCox-transformed values,
and estimates from diagrams of cumulative distribution functions.
Results: The whole sample had a heavily skewed distribution, which approached Gaussian after BoxâCox transformation. The reference limits estimated from small samples were highly variable. The closest estimates to
the 1439-result reference interval for 27-result subsamples were obtained by both parametric and robust methods after BoxâCox transformation but were grossly erroneous in some cases.
Conclusion: For small samples, it is recommended that all values be reported graphically in a dot plot or histogram and that estimates of the reference limits be compared using different methods
Nouvelles approches de la production d'intervalles de référence de populations
Les intervalles de référence décrivent les variations des marqueurs biologiques et sont utilisés quotidiennement par les cliniciens pour interpréter les résultats d'analyses. Ils sont déterminés chez des sujets supposés en bonne santé en tenant compte de nombreux facteurs de variations comme l'ùge ou le sexe. Leur détermination fait l'objet de recommandations internationales et l'objectif de ce travail a été d'en tester l'application dans des cas concrets puis d'évaluer de nouvelles méthodes en suivant principalement deux pistes : d'abord en travaillant sur des échantillons de référence de petite taille (soit en déterminant un intervalle de référence de novo, soit en transférant un intervalle de référence préexistant), ensuite en travaillant sur des échantillons de référence " pollués " par des valeurs issues d'individus non sains. Un outil informatique permettant de répondre rapidement et simplement aux questions précédentes a également été mis au point et est aujourd'hui disponible gratuitement.Reference intervals describe the variations of biological markers and they are commonly used by clinicians to interpret test results. They are determined in healthy individuals and take into account variation factors such as age or sex. Groups of experts are regularly updating the recommendations on "how to determine reference intervals?" The aim of this work was to test the latest international recommendations using practical examples and to test new approaches by two different ways: firstly working on small reference sample groups (determining the reference interval de novo or transferring a pre-existing reference interval), and secondly working on reference sample groups that are "contaminated" by non healthy individuals' test results. An easy-to-use freeware has also been created
Validation of the Medonic CA620/530 Vet 20-ml microcapillary sampler system for hematology testing of feline blood
The aim of the current study was to compare feline hematologic variables in blood collected in
microcapillary tubes (20 ml) and conventional blood tubes with the Medonic CA620/530 Vet in-house
hematologic analyzer. A comparison of results obtained in 60 cats presented at the clinics of the veterinary
school showed that the correlations between the 2 methods were 0.97 for white blood cell, 0.95 for red blood
cell, and 0.93 for platelet counts; 0.92 for hemoglobin concentration; and 0.99 for mean corpuscular volume.
No clinically relevant differences between the 2 blood sampling techniques were observed for any variable,
which suggests that both techniques are interchangeable in cats. Moreover, microcapillary tubes would allow
easier repeated sampling in the same cat and would likely be useful in other small species
Reference values: a review
Reference values are used to describe the dispersion of variables in healthy individuals. They are usually reported as population-based reference intervals (RIs) comprising 95% of the healthy population. International recommendations
state the preferred method as a priori nonparametric determination from at least 120 reference individuals, but acceptable alternative methods include transference or validation from previously established RIs. The most critical steps in the determination of reference values are the selection of reference individuals based on extensively documented inclusion and exclusion criteria and the use of quality-controlled analytical procedures. When only small numbers of values are available, RIs can be estimated by
new methods, but reference limits thus obtained may be highly imprecise. These recommendations are a challenge in veterinary clinical pathology, especially when only small numbers of reference individuals are available
Canine reference intervals for coagulation markers using the STA Satellite and the STA-R Evolution analyzers
The aim of the current study was to determine canine reference intervals for prothrombin time (PT), activated partial thromboplastin time (APTT), fibrinogen, and antithrombin (AT) according to international recommendations. The STA Satellite coefficients of variation of within-laboratory imprecision were 3.9%, 1.3%, 6.9%, and 5.1% for PT, APTT, fibrinogen, and AT, respectively. At 4uC, citrated specimens were stable up to 8 hr for whole blood and 36 hr for plasma, except for APTT, which increased slightly (<1 sec). Nonparametric reference intervals determined in citrated plasma from 139 healthy fasting purebred dogs were 6.9â8.8 sec, 13.1â17.2 sec, 1.24â4.30 g/l, and 104â188% for PT, APTT, fibrinogen, and AT, respectively. Based on PassingâBablok comparison between STA Satellite and STA-R Evolution using 60 frozen specimens from a canine plasma bank, the corresponding reference intervals were transferred to the STA-R Evolution: 7.1â9.2 sec, 12.9â17.3 sec, 1.20â4.43 g/l, and 94â159% for PT, APTT, fibrinogen, and AT, respectively
Comparison of measurements of canine plasma glucose, creatinine, urea, total proteins, alanine aminotransferase, and alkaline phosphatase obtained with the APOLOWAKO and Vitros 250 analyzers
The APOLOWAKO is an entirely automatic benchtop biochemistry analyzer that uses stabilized liquid reagents. It was tested for canine blood and plasma glucose, creatinine, urea, total proteins, alanine aminotransferase, and alkaline phosphatase. The APOLOWAKO gave very similar results for whole blood and the corresponding plasma (n = 32). Within-laboratory imprecision was below 2.2% and 5.8% for substrates and enzymes, respectively. Comparison of results with whole blood by APOLOWAKO and with the corresponding plasma by Vitros 250 (n = 139) showed very good correlations. PassingâBablokâs regression slopes ranged from 0.83 to 1.12 and intercepts were close to zero, except for ALP where the results obtained by APOLOWAKO were approximately 1.5 times higher than by Vitros. The APOLOWAKO system can be a reliable instrument in veterinary practices where larger systems are not available but it should be further validated and reference intervals should be determined
Comparaison de lâexactitude du dosage du sodium et du potassium sanguins chez le chien par les analyseurs ECS 2000 et Vitros 250
La mesure des concentrations plasmatiques de sodium et de potassium est un besoin important en mĂ©decine vĂ©tĂ©rinaire, notamment lors des soins intensifs aux animaux choquĂ©s ; les rĂ©sultats doivent donc ĂȘtre obtenus de façon rapide, prĂ©cise et simple. Lâobjectif de cette Ă©tude a Ă©tĂ© de comparer chez le chien les rĂ©sultats obtenus avec un analyseur de laboratoire validĂ© et soumis Ă un contrĂŽle de qualitĂ©, le Vitros 250, Ă ceux donnĂ©s par lâECS 2000, rĂ©cemment mis sur le marchĂ©. Soixante et onze plasmas hĂ©parinĂ©s canins ont Ă©tĂ© analysĂ©s par les deux appareils ; les rĂ©sultats obtenus sur sang total et plasma par lâECS 2000 ont Ă©tĂ© comparĂ©s sur 36 spĂ©cimens. La corrĂ©lation
entre les résultats des deux analyseurs a été excellente pour le dosage du potassium (KECS = 0,90 x KVitros + 0,29 ; r = 0,96) et satisfaisante pour le dosage du sodium (NaECS = 1,19 x NaVitros - 24,38 ; r = 0,79). Les natrémies
mesurĂ©es par lâECS 2000, avec une imprĂ©cision de 1,2%, ont Ă©tĂ© significativement plus Ă©levĂ©es que celles obtenues par le Vitros 250 avec un biais proportionnel, allant de 0,6 Ă 4,9 mmol/L. Les kaliĂ©mies mesurĂ©es par lâECS 2000, avec une imprĂ©cision de 1,6%, ont Ă©tĂ© modĂ©rĂ©ment mais significativement plus faibles quâavec le Vitros 250 et le biais Ă©tait Ă©galement proportionnel, allant de 0,11 Ă 0,44 mmol/L. La discrimination clinique des rĂ©sultats â normaux â vs. â Ă©levĂ©s â ou â bas â, selon des intervalles de rĂ©fĂ©rence du Vitros 250, a Ă©tĂ© la mĂȘme dans 94% des cas pour le sodium et 90% pour le potassium. Aucune diffĂ©rence significative entre les mesures rĂ©alisĂ©es avec lâECS 2000 sur sang total et sur plasma nâa Ă©tĂ© mise en Ă©vidence
pour la kaliémie, alors que les natrémies déterminées sur sang total ont été significativement plus faibles que celles déterminées sur plasma. Néanmoins, les dosages de K+ et Na+ effectués sur sang total était trÚs fortement
corrĂ©lĂ©s Ă ceux effectuĂ©s sur plasma. La centrifugation du spĂ©cimen nâaugmente donc pas la qualitĂ© analytique de lâappareil et cet analyseur, rapide et facile dâutilisation, constitue une bonne alternative aux analyseurs plus onĂ©reux et techniquement plus dĂ©licats pour les cliniques vĂ©tĂ©rinaires
A new approach for the determination of reference intervals from hospital-based data
Background: Reference limits are some of the most widely used tools in the medical decision process. Their determination is long, difficult, and expensive, mainly because of the need to select sufficient numbers of reference individuals according to well-defined criteria. Data from hospitalized patients are, in contrast, numerous and easily available. Even if all the information required for a direct reference interval computation is usually not available, these data contain information that can be exploited to derive at least rough reference intervals.
Methods: In this article, we propose a method for the indirect estimation of reference intervals. It relies on a
statistical method which has become a gold-standard in other sciences to separate components of mixtures.
It relies on some distributional assumptions that can be checked graphically. For the determination of reference intervals, this new method is intended to separate the healthy and diseased distributions of the measured analyte. We assessed its performance by using simulated data drawn from known distributions and two previously published datasets (from human and veterinary clinical chemistry).
Results and discussion: The comparison of results obtained by the new method with the theoretical data of the simulation and determination of the reference interval for the datasets was good, thus supporting the application of this method for a rough estimation of reference intervals when the recommended procedure cannot be used
Comparaison des techniques de dépistage des protéinuries du Chien
Le dĂ©pistage dâune protĂ©inurie est nĂ©cessaire au diagnostic et au pronostic des affections rĂ©nales du chien. Il repose sur lâutilisation de bandelettes rĂ©actives ou de tests de dĂ©naturation par les acides nitrique ou sulfosalicylique qui
nâont pas Ă©tĂ© validĂ©s chez le Chien. Cette Ă©tude a donc Ă©valuĂ© leur efficacitĂ© dans 151 urines canines par comparaison au dosage quantitatif des protĂ©ines totales dans lâurine par le rouge de pyrogallol. Pour des concentrations protĂ©iques urinaires comprises entre 0,06 g/L et 13,4 g/L, il a Ă©tĂ© montrĂ© que : 1/ les bandelettes dĂ©pistaient toutes les protĂ©inuries supĂ©rieures Ă 0,3 g/L ou 0,5 g/L mais donnaient un pourcentage Ă©levĂ© de faux positifs ; 2/ le test Ă lâacide sulfosalicylique donnait des rĂ©sultats trĂšs dispersĂ©s ; 3/ la rĂ©action de Heller Ă lâacide nitrique ne donnait que trĂšs peu de faux positifs au seuil de 0,5 g/L. En pratique, le caractĂšre permanent dâune protĂ©inurie devant ĂȘtre dĂ©montrĂ© par la rĂ©pĂ©tition des analyses au moins trois fois Ă au moins deux semaines dâintervalle, les bandelettes sont des moyens suffisants avant dâaborder la quantification de la protĂ©inurie et/ou la dĂ©termination du rapport protĂ©ines/crĂ©atinine urinaire
Comparaison des rĂ©sultats dâanalyses urinaires rapides en fonction du type de bandelette rĂ©active utilisĂ©
Objectif.â Cette Ă©tude a comparĂ© les rĂ©sultats dâanalyses urinaires obtenus par quatre marques diffĂ©rentes de bandelettes urinaires.
MatĂ©riel et mĂ©thode.â Cette Ă©tude clinique prospective a Ă©tĂ© menĂ©e sur 85 Ă©chantillons dâurine provenant de quatre espĂšces, sĂ©lectionnĂ©es sur le seul critĂšre du volume disponible. Les bandelettes multiparamĂ©triques testĂ©es ont Ă©tĂ© les suivantes : Combur 10 Test ([C]Roche, Scil, Strasbourg, France), Multistix ([M]Bayer Diagnostics, Tarrytown, Ătats-Unis), Combiscreen ([CS]Analyticon Biotechnologies AG, Lichtenfels, Allemagne), URS-10 ([U]Teco Diagnostics, Anahein, Ătats-Unis). Toutes les analyses ont Ă©tĂ© faites par la mĂȘme personne, dans un dĂ©lai
infĂ©rieur Ă 15 minutes et les rĂ©sultats ont Ă©tĂ© obtenus en comparant visuellement les colorations des bandelettes aux grilles dâinterprĂ©tation fournies par ces fabricants. La comparaison des rĂ©sultats a reposĂ©, analyte par analyte, sur le calcul du pourcentage dâaccord entre les bandelettes et sur leur comparaison deux Ă deux par le test kappa.
RĂ©sultats.â Les principes analytiques et la structure des bandelettes sont similaires. Les gammes analytiques et de couleur sont trĂšs semblables. Le pourcentage dâaccord entre les bandelettes est excellent Ă trĂšs bon pour toutes les plages Ă lâexception des plages « densitĂ© » et « pH ».
Discussion.â La grande similaritĂ© technique des bandelettes laissait supposer le fort pourcentage dâaccord entre les bandelettes. Selon la marque, les Ă©chelles semi-quantitatives des bandelettes nâont pas la mĂȘme valeur. Les conditions de conservation et dâutilisation des
bandelettes sont la principale source dâerreur