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Background: The current dogma of establishing intra-laboratory reference limits (RLs) and their periodical reviewing cannot be fulfilled by most laboratories due to the expenses involved. Thus, most laboratories adopt RLs from external sources often neglecting the problems of transferability. Presently accepted validation concepts still require experimental expenses. Several attempts were undertaken to derive RLs from the large data pools stored in modern laboratory information systems. Former indirect procedures were not generally accepted, but were recently further developed and combined with direct exclusion criteria and applied to estimate RLs of the catalytic activity concentrations of enzymes. This approach was now applied to several electrolytes in serum and plasma most commonly applied in clinical chemistry.Methods: A smoothed kernel density function was estimated for the distribution of the mixed data of the sample group (combined data of non-diseased and diseased subjects). It was assumed that the 'central' part of the distribution of all data represents the non-diseased ('healthy') population (non-pathological values) with high probability. The central part was defined by truncation points using an optimisation method, and was used to estimate a Gaussian distribution of the values of non-diseased subjects. This distribution was now considered as the distribution of the non-diseased subgroup. The percentiles of this parametrical distribution were calculated to obtain unimodal reference intervals.Results: The RLs obtained from different laboratories were similar to recently published values established by direct procedures. Stratification for gender was not necessary, but in some cases for age. With rising age, an increase of the upper RL and of the reference range was observed for potassium. Hospitalisation affected the RLs of sodium, potassium, calcium and magnesium, but not of phosphate. In the case of sodium, the data of at least five regional laboratories could be combined to common RLs. The presented indirect procedure was further validated with a large dataset of potassium concentrations from the NHANES III study with five groups of different health status.Conclusions: The proposed strategy of combining exclusion criteria with an indirect method led to RLs from intra-laboratory data pools for electrolytes which were plausible in comparison to published data obtained by the generally accepted direct approach. The combined concept, however, still requires further investigations. Therefore, it is presently only recommended for checking and reviewing already existing RLs. [ABSTRACT FROM AUTHOR]

Blood and serum values in the Göttingen miniature pig 6. Effect of endogenous and exogenous factors on parameters of carbohydrate metabolism and of acid-base balance as well as on blood sedimentation: In the present series of communications on blood and serum values of the Göttingen miniature pig emphasis is placed on the importance of endogenous and exogenous factors for reference values. The investigation involved 120 pigs of the white and 84 pigs of the coloured line. The experimental animals were 60 to 276 days old and had been selected for this investigation. In a special preliminary experiment (catheter programme) the effect of blood sampling method on the predictive value of the results was studied. In the present communication its effect on parameters of carbohydrate metabolism and of acid-base balance as well as on blood sedimentation is considered. Under the present experimental conditions the following resultats were obtained: 1. Catheter and puncture methods provide different predictive values for the various groups of parameters. For investigating the parameters of carbohydrate metabolism and acid-base balance the catheter method is recommended, while for investigating blood sedimentation puncturing of the animals is more advantageous. 2. Parameters of carbohydrate metabolism and of acid-base balance, except pH value, show normal distributions. For pH about 70 % and for blood sedimentation nearly 80 % of all values are within one standard deviation. Variability of pH value is low also with puncturing. 3. All parameters are age-related. For blood sedimentation the two endogenous factors, genetic line and sex, must be considered in addition. 4. Due to the high heritability of the parameters studied the animals' relationships with one another must be taken into account mainly in the case of blood sedimentation results and they should be controlled in lactate analysis. Under the present conditions (puncturing) those exogenous factors not related to the blood sampling method are of minor importance. Zusammenfassung In der vorliegenden Mitteilungsreihe über Blut- und Serumwerte des Göttinger Miniaturschweines wird insbesondere auf die Bedeutung endogener und exogener Faktoren für den Referenzwert hingewiesen. Im Untersuchungsprogramm standen 120 Tiere der weißen und 84 Tiere der bunten Linie im Altersabschnitt vom 60. bis zum 276. Lebenstag. Sie waren speziell für diese Untersuchung zusammengestellt worden. In einem gesonderten Vorversuch ('Katheterprogramm') wurde an 16 Tieren der Einfluß der Blutentnahmemethode auf die Aussagefähigkeit von Untersuchungsergebnissen überprüft. In dieser Mitteilung werden Merkmale des Kohlenhydratstoffwechsels, des Säure-Basen-Haushaltes und die Blutkörperchensenkung zusammengefaßt. Unter den gegebenen Bedingungen gehen folgende Ergebnisse hervor: 1. Katheter- und Punktionswerte haben für keine Merkmalsgruppe eine gleichwertige Aussagefähigkeit. Für die Merkmale des Kohlenhydratstoffwechsels und für den Säure-Basen-Haushalt wird der Katheter, für die Blutkörperchensenkung die Punktion der Tiere anempfohlen. 2. Die Merkmale des Kohlenhydratstoffwechsels und des Säure-Basen-Haushaltes sind - mit Ausnahme des pH - in etwa normalverteilt. Beim pH liegen etwa 70 %, bei der BSG fast 80 % aller Werte innerhalb einer Standardabweichung. Die Variabilität des pH ist auch bei Punktion der Tiere niedrig. 3. Alle Merkmale sind altersabhängig. Bei der Blutkörperchensenkung sind zudem die endogenen Faktoren Linie und Geschlecht zu beachten. 4. Aufgrund der hohen Heritabilität sind insbesondere bei der BSG die Verwandtschaftsverhältnisse der Tiere zu beachten, und sie sollten beim Lactat überprüft werden. Unter den gegebenen Bedingungen (Punktion) haben die nicht der Blutentnahme zugeordneten exogenen Faktoren eine eher bescheidene Relevanz. [ABSTRACT FROM AUTHOR]

Blood and serum values in the Göttingen miniature pig 5. Influence of endogenous and exogenous factors on serum electrolytes: In this communication attention is drawn to the influence of endogenous and exogenous factors on blood serum reference values. Under the experimental conditions of the investigation the following results were obtained: 1. Catheter and puncture values provide nearly the same information for all electrolytes studied. However, this is valid only with some reservation as the electrolytes varied within relatively narrow limits and, furthermore, in a rather unsystematic way so as to provide an unfavourable basis for statistical analysis. 2. Most of the electrolytes studied show a normal distribution. Only calcium is an exception. 3. There is some influence of genetic line on iron, age, on phosphorus and of degree of relationship on inorganic phosphorus and calcium. In castrated males the effect of sex on electrolytes is only small. 4. There is evidence of a high systematic environmental effect on potassium. Therefore, standardized experimental conditions and maximum welfare of the animals are of the utmost importance also for the reliability of the results. Zusammenfassung In der vorliegenden Mitteilungsreihe über Blut- und Serumwerte beim Göttinger Miniaturschwein wird insbesondere die Bedeutung endogener und exogener Faktoren für den Referenzwert angesprochen. Unter den gegebenen Versuchsbedingungen kann für die Serumelektrolyte folgendes festgestellt werden: 1. Katheter- und Punktionswerte haben in etwa eine gleichwertige Aussagefähigkeit. Diese Feststellung gilt jedoch nur eingeschränkt, weil sich die Merkmale zumeist in relativ engen Grenzen und dort wiederum unsystematisch veränderten, so daß die Voraussetzungen für die statistische Analyse ungünstig ausfallen mußten. 2. Die Merkmale sind weitgehend normalverteilt, lediglich das Calcium erfüllt die Voraussetzungen nicht. 3. Die Linie hat nur beim Merkmal Eisen, das Alter bei den Phosphorwerten, der Verwandtschaftsgrad beim anorganischen Phosphor und Calcium eine größere Bedeutung. Das Geschlecht hat bei Kastration der männlichen Tiere nur minimale Einflüsse. 4. Beim Kalium konnte eine hohe systematische Umweltabhängigkeit nachgewiesen werden; eine Standardisierung der Versuchsbedingungen bei größtmöglichem Wohlbefinden der Tiere ist somit auch für die Aussagefähigkeit des Experiments von besonderem Interesse. [ABSTRACT FROM AUTHOR]