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 Box–Cox-transformed values, 2.5th and 97.5th percentiles by a robust method on native and Box–Cox-transformed values, and estimates from diagrams of cumulative distribution functions. Results: The whole sample had a heavily skewed distribution, which approached Gaussian after Box–Cox 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 Box–Cox 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

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 6.9–8.8 sec, 13.1–17.2 sec, 1.24–4.30 g/l, and 104–188% for PT, APTT, fibrinogen, and AT, respectively. Based on Passing–Bablok 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: 7.1–9.2 sec, 12.9–17.3 sec, 1.20–4.43 g/l, and 94–159% for PT, APTT, fibrinogen, and AT, respectively

Continuous control of ionization wave chaos by spatially derived feedback signals

In the positive column of a neon glow discharge, two different types of ionization waves occur simultaneously. The low-dimensional chaos arising from the nonlinear interaction between the two waves is controlled by a continuous feedback technique. The control strategy is derived from the time-delayed autosynchronization method. Two spatially displaced points of observation are used to obtain the control information, using the propagation characteristics of the chaotic wave.Comment: Elsevier-Tex-File, 8 pages, 6 figures, submitted to PL

Curved plasma channels: Kerr lens and Airy prism

We analytically calculate the transverse energy fluxes that would be respectively induced in high-power Airy beams by the Kerr self-focusing and the Airy profile itself if they were the only active process. In experimental condition representative of laser filamentation experiments of high-power ultrashort laser pulses in air and condensed media, the Kerr lens induces transverse energy fluxes much larger than the Airy "prism" at the main peak. As a consequence, the curved plasma channels in Airy beams are not only a plasma spark on a curved focus, but indeed self-guided filaments, and their curved trajectory appears as a perturbation due to the linear Airy propagation regime.Comment: 10 pages, 4 figures (6 panels

Magnetic field and pressure effects on charge density wave, superconducting, and magnetic states in Lu5_5Ir4_4Si10_{10} and Er5_5Ir4_4Si10_{10}

We have studied the charge-density-wave (CDW) state for the superconducting Lu$_5$Ir$_4$Si$_{10}$ and the antiferromagnetic Er$_5$Ir$_4$Si$_{10}$ as variables of temperature, magnetic field, and hydrostatic pressure. For Lu$_5$Ir$_4$Si$_{10}$, the application of pressure strongly suppresses the CDW phase but weakly enhances the superconducting phase. For Er$_5$Ir$_4$Si$_{10}$, the incommensurate CDW state is pressure independent and the commensurate CDW state strongly depends on the pressure, whereas the antiferromagnetic ordering is slightly depressed by applying pressure. In addition, Er$_5$Ir$_4$Si$_{10}$ shows negative magnetoresistance at low temperatures, compared with the positive magnetoresistance of Lu$_5$Ir$_4$Si$_{10}$.Comment: 12 pages, including 6 figure

Comparaison de l’exactitude 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 médecine vétérinaire, notamment lors des soins intensifs aux animaux choqués ; les résultats doivent donc être obtenus de façon rapide, précise et simple. L’objectif de cette étude a été de comparer chez le chien les résultats obtenus avec un analyseur de laboratoire validé et soumis à un contrôle de qualité, le Vitros 250, à ceux donnés par l’ECS 2000, récemment mis sur le marché. Soixante et onze plasmas héparinés canins ont été analysés par les deux appareils ; les résultats obtenus sur sang total et plasma par l’ECS 2000 ont été comparés sur 36 spécimens. La corrélation 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 mesurées par l’ECS 2000, avec une imprécision de 1,2%, ont été significativement plus élevées que celles obtenues par le Vitros 250 avec un biais proportionnel, allant de 0,6 à 4,9 mmol/L. Les kaliémies mesurées par l’ECS 2000, avec une imprécision de 1,6%, ont été modérément mais significativement plus faibles qu’avec le Vitros 250 et le biais était également proportionnel, allant de 0,11 à 0,44 mmol/L. La discrimination clinique des résultats “ normaux ” vs. “ élevés ” ou “ bas ”, selon des intervalles de référence du Vitros 250, a été la même dans 94% des cas pour le sodium et 90% pour le potassium. Aucune différence significative entre les mesures réalisées avec l’ECS 2000 sur sang total et sur plasma n’a été mise en évidence 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 très fortement corrélés à ceux effectués sur plasma. La centrifugation du spécimen n’augmente donc pas la qualité analytique de l’appareil et cet analyseur, rapide et facile d’utilisation, constitue une bonne alternative aux analyseurs plus onéreux et techniquement plus délicats pour les cliniques vétérinaires