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PubMed1992

Effects of oxygen toxicity on cuprolinic blue-stained proteoglycans in alveolar basement membranes.

Effects of oxygen toxicity on distribution and density of proteoglycans in basement membranes of newborn rat lungs were assessed by electron microscopic analysis of tissues processed with cuprolinic blue, a cationic label that characteristically labels these anionically charged macromolecules. Newborn rats placed in greater than 95% oxygen at birth were killed at weekly intervals for 4 wk, and lung tissues fixed in 2.5% glutaraldehyde with 0.2% cuprolinic blue were processed for electron microscopy. Alveolar basement membranes from oxygen-treated and control animals were compared for differences in thickness and proteoglycan concentration and distribution. Results showed progressive thickening of alveolar basement membranes with increased duration of oxygen exposure. The normal distribution of proteoglycans, which is predominantly in the lamina rara externa of alveolar basement membranes, was frequently lost in thickened membranes found in oxygen-treated animals. Density of proteoglycans in these membranes decreased to 56% of normal by 2 wk of age and remained low with continued oxygen administration. Proteoglycan concentration in basement membranes on the interstitial side of alveolar capillaries in both control and oxygen-treated animals was low compared with proteoglycan concentration in basement membranes that opposed the alveolar air space, and administration of oxygen diminished these differences. These results demonstrate a direct alteration of proteoglycan distribution and density in the developing lung as a result of oxygen toxicity. This could result in decreased cell adhesion, influence the cellular response to lung injury, and contribute to the increased permeability seen with this disorder.

Animals↗

PubMed2003

Shrinkage-based similarity metric for cluster analysis of microarray data.

The current standard correlation coefficient used in the analysis of microarray data was introduced by M. B. Eisen, P. T. Spellman, P. O. Brown, and D. Botstein [(1998) Proc. Natl. Acad. Sci. USA 95, 14863-14868]. Its formulation is rather arbitrary. We give a mathematically rigorous correlation coefficient of two data vectors based on James-Stein shrinkage estimators. We use the assumptions described by Eisen et al., also using the fact that the data can be treated as transformed into normal distributions. While Eisen et al. use zero as an estimator for the expression vector mean mu, we start with the assumption that for each gene, mu is itself a zero-mean normal random variable [with a priori distribution N(0,tau 2)], and use Bayesian analysis to obtain a posteriori distribution of mu in terms of the data. The shrunk estimator for mu differs from the mean of the data vectors and ultimately leads to a statistically robust estimator for correlation coefficients. To evaluate the effectiveness of shrinkage, we conducted in silico experiments and also compared similarity metrics on a biological example by using the data set from Eisen et al. For the latter, we classified genes involved in the regulation of yeast cell-cycle functions by computing clusters based on various definitions of correlation coefficients and contrasting them against clusters based on the activators known in the literature. The estimated false positives and false negatives from this study indicate that using the shrinkage metric improves the accuracy of the analysis.

Algorithms↗

PubMed2000

Case management for people with severe mental disorders.

BACKGROUND: Since the 1960s, in many parts of the world, large psychiatric were closed down and people were treated in outpatient clinics, day centres or community mental health centres. Rising readmission rates suggested that this type of community care may be less effective than anticipated. In the 1970s case management arose as a means of co-ordinating the care of severely mentally ill people in the community. OBJECTIVES: To determine the effects of case management as an approach to caring for severely mentally ill people in the community. Case management was compared against standard care on four main indices: (i) numbers remaining in contact with the psychiatric services; (ii) extent of psychiatric hospital admissions; (iii) clinical and social outcome; and (iv) costs. SEARCH STRATEGY: Electronic searches of CINAHL (1997), the Cochrane Schizophrenia Group's Register of trials (1997), EMBASE (1980-1995), MEDLINE (1966-1995), PsycLIT (1974-1995) and SCISEARCH (1997) were undertaken. References of all identified studies were searched for further trial citations. SELECTION CRITERIA: The inclusion criteria were that studies should be randomised controlled trials that (i) had compared case management to standard community care; and (ii) had involved people with severe mental disorder mainly between the ages of 18-65. Studies of case management were defined as those in which the investigators described the intervention as 'case' or 'care' management rather than 'Assertive Community Treatment' or 'ACT'. DATA COLLECTION AND ANALYSIS: A study was carried out to test the reliability of the inclusion criteria. Categorical data were extracted twice and then cross-checked, any disagreements being resolved by discussion. Odds ratios and the number needed to treat were estimated. Continuous data collected by a measuring instrument was only included if the instrument (i) had been described in a peer-reviewed journal; (ii) was a self-report or had been completed by an independent rater; and (iii) provided a summary score for a broad area of functioning. Normally distributed continuous data were included if means and standard deviations were available. Non-normal data were included if analysed either after transformation or using non-parametric methods. Tests for heterogeneity were conducted. MAIN RESULTS: Case management increased the numbers remaining in contact with services (for case management odds ratio = 0.70; 99%CI 0.50-0. 98; n=1210). Case management approximately doubled the numbers admitted to psychiatric hospital (OR 1.84; 99% CI 1.33-2.57; n=1300). Except for a positive finding on compliance, from one study, case management showed no significant advantages over standard care on any psychiatric or social variable. Cost data did not favour case management but insufficient information was available to permit definitive conclusions. REVIEWER'S CONCLUSIONS: Case management ensures that more people remain in contact with psychiatric services (one extra person remains in contact for every 15 people who receive case management), but it also increases hospital admission rates. Present evidence suggests that case management also increases duration of hospital admissions, but this is not certain. Whilst there is some evidence that case management improves compliance, it does not produce clinically significant improvement in mental state, social functioning, or quality of life. There is no evidence that case management improves outcome on any other clinical or social variables. Present evidence suggests that case management increases health care costs, perhaps substantially, although this is not certain. In summary, therefore, case management is an intervention of questionable value, to the extent that it is doubtful whether it should be offered by community psychiatric services. It is hard to see how policy makers who subscribe to an evidence-based approach can justify retaining case management as 'the cornerstone' of community mental hea

Case Management↗

PubMed2007

Physico-chemical characterization of nanofiltration membranes.

This study presents a methodology for an in-depth characterization of six representative commercial nanofiltration membranes. Laboratory-made polyethersulfone membranes are included for reference. Besides the physical characterization [molecular weight cut-off (MWCO), surface charge, roughness and hydrophobicity], the membranes are also studied for their chemical composition [attenuated total reflectance Fourier spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS)] and porosity [positron annihilation spectroscopy (PAS)]. The chemical characterization indicates that all membranes are composed of at least two different layers. The presence of an additional third layer is proved and studied for membranes with a polyamide top layer. PAS experiments, in combination with FIB (focused ion beam) images, show that these membranes also have a thinner and a less porous skin layer (upper part of the top layer). In the skin layer, two different pore sizes are observed for all commercial membranes: a pore size of 1.25-1.55 angstroms as well as a pore size of 3.20-3.95 angstroms (both depending on the membrane type). Thus, the pore size distribution in nanofiltration membranes is bimodal, in contrast to the generally accepted log-normal distribution. Although the pore sizes are rather similar for all commercial membranes, their pore volume fraction and hence their porosity differ significantly.

Journal Article↗

PubMed2004

Hierarchical modelling of small area and hospital variation in short-term prognosis after acute myocardial infarction. A longitudinal study of 35- to 74-year-old men in Denmark between 1978 and 1997.

Models for analysis of trends in hospital and small area variation in case fatality after acute myocardial infarction are presented. The data are from administrative registries in Denmark. Hierarchical modelling in a logistic regression with a Bayesian approach is used. Model selection is undertaken using the deviance and the Bayesian information criteria. There is a modest trend for hospital variation in case-fatality rates that coincides with the introduction of new treatment strategies. This hospital variation is considerably larger than the variation at the area level. There is no trend for variation of the case-fatality rates at the area level. Unstructured random effects slightly outperform spatially correlated random effects at the area level. Somewhat high correlations over time within hospitals and within areas were detected for the case-fatality rates. Heavy-tailed distributions (T-distributions) could be an alternative for the random effect distribution in data from administrative registries and compete in the model selection with the normal distribution in this study.

Adult↗

PubMed2001

Epithelial development and differentiation in the mammary gland is not dependent on alpha 3 or alpha 6 integrin subunits.

In the mammary gland, both laminin and integrins have been shown to be required for normal ductal morphogenesis during development in vivo, and for functional differentiation in culture models. Major integrin receptors for laminins in the mammary gland are alpha 3 beta 1, alpha 6 beta 1, and alpha 6 beta 4. However, the specific subunits that contribute to laminin-mediated mammary cell function and development have not been identified. In this study, we use a genetic approach to test the hypothesis that laminin-binding integrins are required for the function of the mammary gland in vivo. Rudiments of embryonic mammary gland were shown to develop in the absence of these integrin subunits. Postnatal development of the mammary gland was studied in integrin null tissue that had been transplanted into the mammary fat pads of syngeneic hosts. In mammary epithelium lacking alpha 6 integrin, the beta 4 subunit was not apparent and hemidesmosome formation was only rudimentary. However, despite this deficiency, normal ductal morphogenesis and branching of the mammary gland occurred and myoepithelial cells were distributed normally with respect to luminal cells. Mammary alveoli devoid of alpha 3 or alpha 6 integrin formed in pregnancy and were histologically and functionally identical to those in wild-type mammary gland. The tissue underwent full morphological differentiation, and the epithelial cells retained the ability to synthesize beta-casein. This work demonstrates that mammary tissue genetically lacking major laminin-binding integrin receptors is still able to develop and function.

Animals↗

PubMed1982

Recurrent decreases of erythrocyte electrophoretic mobility in rats exposed to 1.0 R whole-body x-radiation.

Circulating erythrocytes from rats were examined up to 30 weeks post whole-body exposures of 1.0 R for alterations in the expression of net negative surface charge as measured by whole-cell microelectrophoresis in saline sorbitol. Erythrocyte electrophoretic mobility was determined in an apparatus composed of a horizontal transilluminated cylindrical chamber, equipped with a reversible, blacked platinum electrode, immersed in a water bath maintained at 25.0 +/- 1.0 degree C (Rank Brothers). In two separate experiments, recurrent decreases in the expression of net negative surface charge occurred at 10, 17, and 30 weeks post-irradiation. At these times distributional analyses of recorded erythrocyte electrophoretic mobility (EEPM) values revealed a skewing of the normally distributed EEPM population values to lower EEPM. Total sialic acid content released from hydrolyzed erythrocyte membrane preparations revealed no significant differences between erythrocytes from sham and irradiated animals. In vivo post-irradiation labeling of erythrocytes with diisopropyl-[32P] phosphorofluoridate at 4 and 33 weeks (separate experiments) indicated only a minor abbreviated erythrocyte life span at 33 weeks. Therefore, effects from low dose (1.0 R) whole-body irradiation would appear to include a recurrent defect in the expression of the net negative surface charge.

Animals↗

PubMed1987

Measurements of serum-free thyroid hormone concentrations by ultrafiltration--a comparison with equilibrium dialysis and mathematical calculation.

An ultrafiltration method (UF) for measuring free thyroxine (FT4) and free triiodothyronine (FT3) using the Diaflow YM membrane (Centricon-10) is described. The results are compared with those by equilibrium dialysis (ED) and also by mathematical calculations derived from T4, T3, and binding protein concentrations. The precision with the UF method was excellent. The normal ranges of FT4 and FT3 by the three methods are all comparable. There was a high degree of correlation of FT4 or FT3 results by UF with those by ED and by calculation (r = 0.940-0.974, n = 161, P less than 0.001). FT4 and FT3 by all methods agreed well for hyperthyroidism, hypothyroidism, and for patients with low T4-binding globulin. The mean FT3 in pregnancy was lower than the normal value for all methods, and FT4 concentrations by UF and calculation also decreased in late pregnancy. The mean FT4 by UF and ED in low T3 syndrome were significantly higher than in the normal controls, while the calculated FT4 was lower. The FT3 in low T3 syndrome distributed normal to subnormal in all methods. These results indicate that a) the UF method is a reliable reference method for measuring FT4 and FT3 concentrations; b) the UF results agree well with those by ED and also with theoretically derived values in subjects with thyroid diseases and TBG abnormalities; c) for patients with low T3 syndrome, the FT4 results obtained by UF and ED are similarly discrepant from the calculated results, implying the existence of binding inhibitor(s) which affect both UF and ED measurements.

Adult↗

PubMed1999

Comparison of MPTP-induced changes in spontaneous neuronal discharge in the internal pallidal segment and in the substantia nigra pars reticulata in primates.

The basal ganglia are currently viewed as components of segregated corticosubcortical reentrant circuits. One of these circuits, the "motor" circuit, is critically involved in the development of parkinsonian motor signs. Current pathophysiologic models postulate that parkinsonism is associated with increased activity in the basal ganglia output nuclei. The neuronal activity in the motor portion of one of these output nuclei, the internal segment of the globus pallidus (GPi), has been characterized in detail in intact and parkinsonian animals, but the neuronal activity in the second major basal ganglia output nucleus, the substantia nigra pars reticulata (SNr), has received far less attention. This study in primates represents a comparison of the effects of parkinsonism, induced by injections of the dopaminergic neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), on the neuronal discharge in the GPi and SNr. These electrophysiologic recording experiments were carried out in three African green and two rhesus monkeys. One hundred and twenty-four neurons were recorded in the GPi before treatment with MPTP, and 93 neurons thereafter. In the SNr, 55 cells were recorded before treatment with MPTP, and 41 cells thereafter. MPTP induced a non-significant increase in the average discharge rate and a significant decrease in the median interspike interval length (ISI) in the GPi (by 13%), whereas no changes were detected in either parameter in the SNr. The average ISI distributions were markedly asymmetric in both structures, and could be modeled by a logarithmic normal distribution. With the MPTP treatment, the mode of the ISI distribution fell by 24% in the GPi (P< or =0.01), whereas it did not change significantly in the SNr. An algorithm that detects burst discharges in the raw ISI data (based on the method by Legendy and Salcman) detected a significant increase in the proportion of action potentials that participated in bursts of discharge in both structures (increase by 257% in the GPi, and by 67% in the SNr). Power spectral and autocorrelation analysis revealed that treatment with MPTP increased the proportion of cells with oscillatory burst patterns at 3-8 Hz in both structures (from 0.8% to 27% of all neurons in the GPi, and from none to 10% in the SNr). The results show that neuronal discharge in the SNr is affected in parkinsonism, but that the changes in the SNr are less pronounced then those seen in the GPi.

Animals↗

PubMed2001

Migration of fallout-radionuclides in the soil: effect of non-uniformity of the sorption properties on the activity-depth profiles.

Experimentally observed activity-depth profiles of fallout radionuclides in the soil frequently exhibit a comparatively fast moving tail in soil layers below the peak concentration (tailing). Monte Carlo calculations on the basis of the convection-dispersion model show that this phenomenon can be explained by assuming that either the hydraulic properties of the soil (characterised by the diffusion/dispersion coefficient and pore water velocity) or the sorption properties of the soil (characterised by the distribution coefficient Kd), or both, exhibit a horizontal variability according to a log-normal distribution. Modifications of the activity-depth profile due to a Kd value which decreases linearly with depth were examined by using a random walk approach, based also on the convection-dispersion model. In this case, however, a pronounced tailing effect of the activity-depth profile did not result. Interpretation and realistic modelling of an experimentally observed activity-depth profile which exhibits a tailing effect is thus not unambiguously possible without any additional information on the spatial variability of the hydraulic parameters and, independently, also for the sorption properties.

Absorption↗

PubMed2006

Derivative ratio as a measure of effect: sex over age of occurrence of myocardial infarction in Brazil.

The concept of relative risk (RR) as an incidence rate ratio is extended to a ratio of derivatives of cumulative occurrences of events with respect to any continuous variable whose domain is partitioned in sub-domains of study and referent groups to be contrasted. RR, thus expressed as a function, allows the identification of key values of the independent variable through which effect, as a relation between sub-domains, is modulated. The effect of sex over age of occurrence of myocardial infarction in a sample of Brazilian patients is analysed. Male sex, as contrasted to female, is acknowledged as a risk factor for the disease but it is known that this risk wanes with aging. Derivatives of cumulative occurrences with respect to age are calculated for men and women. Given the normal distribution of these occurrences, derivatives are found to be very similar to the corresponding normal density functions, with difference not greater than 0.005. This provides an easy way of identifying the derivatives whose ratio is likewise easily calculated. Results suggest that, in the Brazilian sample of patients studied, the greatest men to women RR is 1.9 at the age of 23.5 years and that at the age of 61.2 years risks become evens.

Adult↗

PubMed1992

Bimodality of plasma apolipoprotein B levels in familial combined hyperlipidemia.

To investigate possible genetic influences on plasma apolipoprotein (apo) B levels in familial combined hyperlipidemia (FCHL), commingling analysis was performed on data from seven large kindreds, including 183 individuals. The overall frequency distribution of apo B was skewed and was compatible with the presence of two normally distributed subdistributions (mean values, 117 and 172 mg/dl). The analysis was repeated after stratification of individuals by low density lipoprotein (LDL) subclass phenotype. Among subjects with phenotype A (predominance of large, buoyant LDL), a single apo B distribution was found (mean, 115 mg/dl). Among subjects with phenotype B (predominance of small, dense LDL), the distribution was bimodal, with mean values, 116 and 167 mg/dl, similar to the unstratified data set. Thus the skewing of the overall apo B distribution in FCHL family members may be due to a distinct subset of individuals with phenotype B who are genetically susceptible to even higher elevations of apo B. The higher apo B/phenotype B subjects also showed significantly higher levels of triglyceride and LDL-cholesterol than the lower apo B/phenotype B subjects. The lower apo B/phenotype B subjects had higher triglyceride and lower LDL-cholesterol than the phenotype A subjects. The enhanced information regarding apo B and lipid levels in the three subgroups of individuals identified here may facilitate a better understanding of genetic susceptibility to coronary heart disease.

Adolescent↗

PubMed1986

Simulation of the spatial distribution of muscle fibres in human muscles.

A composite muscle cross section model was simulated on a VAX 780 computer. The various motor unit territories in the cross section area were circular, partially overlapping each other. The radii of the territories of the motor units, their centres, and the number of muscle fibres in each motor unit were treated as random variables. Two different models were generated, one with a uniform distribution of the fibres in the motor unit territories, and the other with a normal distribution of the fibres. An algorithm for simulation of fibre density measurements was written, and the effects of varying the parameters of the model on fibre density measurements were investigated. The results of the computer simulation were in agreement with analytical and laboratory findings.

Computers↗

PubMed1985

A threshold model for punctuated gradualism.

A model for continuous and discontinuous evolutionary change is proposed that accommodates both punctuated equilibrium and phyletic gradualism. Natural selection operating on a gaussian distribution of phenotypes subjected to severe stress will result in a skewing of the normal distribution in the direction of the favoured phenotype. If a reproductive isolation threshold is imposed upon this model, rapid crossing of the threshold by large numbers of individuals within the skewed distribution will result in the sudden achievement of a critical descendant population mass. Mild directional selection however, will result in gentle shifts of the gaussian mean thus leading us to suggest that stasis and incipient speciatior are extremes of the same spectrum, defined by the rates of mean-shift in response to varying severities of selection pressure. Both punctuated and gradualistic evolution as accommodated in our model may further be described within Thom's cusp catastrophe theory.

Biological Evolution↗

PubMed2004

Activity size distributions of some naturally occurring radionuclides 7Be, 40K and 212Pb in indoor and outdoor environments.

The activity size distributions of natural radionuclides (7)Be and (40)K were measured outdoor in El-Minia city, Egypt by means of gamma spectroscopy. A low-pressure Berner cascade impactor was used as a sampling device. The activity size distribution of both (7)Be and (40)K was described by one log-normal distribution, which was represented by the accumulation mode. The activity median aerodynamic diameter (AMAD) of (7)Be and (40)K was determined to be 530 and 1550 nm with a relative geometric standard deviation (delta, which was defined as the dispersion of the peak) of 2.4 and 2, respectively. The same sampling device (Berner impactor) and a screen diffusion battery were used to measure the activity size distribution, activity concentration and unattached fraction (f(P)) of (212)Pb in indoor air of El-Minia City, Egypt. The mean activity median aerodynamic diameter (AMAD) of the accumulation mode for attached (212)Pb was determined to be 250 nm with a mean geometric standard deviation (delta) of 2.6. The mean value of the specific concentration of (212)Pb associated with that mode was determined to be 460+/-20 mBq m(-3). The activity median thermodynamic diameter (AMTD) of unattached (212)Pb was determined to be 1.25 nm with delta of 1.4. A mean unattached fraction (f(p)) of 0.13+/-0.02 was obtained at a mean aerosol particle concentration of 1.8 x 10(3) cm(-3). The mean activity concentration of unattached (212)Pb was found to be 19+/-3 mBq m(-3). It was found that the aerosol concentration played an important role in varying the unattached, attached activity concentration and unattached fraction (f(P)).

Journal Article↗

PubMed2001

Expiratory and inspiratory forced vital capacity and one-second forced volume in asymptomatic never-smokers in Norway.

The objectives of this study were to examine within and between individual variation detected during forced expiratory (FE) and forced inspiratory (FI) manoeuvers in a general population and to investigate the dependence of these variables on age, body size, and gender. A random sample of asymptomatic never smokers who had never been exposed occupationally to quartz or asbestos and who were living on the south-western coast of Norway were examined by spirometry; 81% of the individuals invited to attend did so. Of the 488 subjects between 18 and 73 years of age, 98% contributed three acceptable recordings for forced expiratory vital capacity (FVC) and one-second forced expiratory volume (FEV1), 94% contributed three acceptable recordings for forced inspiratory vital capacity (FIVC) and 85% contributed three acceptable recordings for one-second forced inspiratory volume (FIV(1)). The within-subject variation increased with body height and was considerably larger for FIV(1) than for FVC, FEV(1) or FIVC. A four-parameter model of pulmonary function measurement divided by height squared, including a gender term and a linear and quadratic term of age, fit the median of the observed values well. The residuals had a close-to-normal distribution, and the fifth-percentile values were estimated as the lower limit of normal. The peak value of dynamic lung volumes was observed into the middle of the fourth decade of life, and the decline thereafter did not differ greatly between the genders or among the different indices. The forced inspiratory volumes are the first reported in any reference population.

Adolescent↗

PubMed1999

Normal ranges and reproducibility of statistical, geometric, frequency domain, and non-linear measures of 24-hour heart rate variability.

Diabetic cardiovascular autonomic neuropathy (CAN) carries an increased risk of mortality. The early detection and characterization of CAN has traditionally been based on the results of autonomic reflex tests (AFTs). A variety of different measures to quantify 24-hour heart rate variability (HRV) have recently been introduced, but their normal ranges, reliability, and validity in patients with CAN have not been adequately studied. We established the normal ranges of statistical (SDNN index, CV, SNN50, RMSSD), geometric (triangular index (TI), triangular interpolation (TINN), top angle index [TAI]), frequency domain (spectral power in the VLF, LF, and HF bands, LF/HF ratio, LF in normalized units [NU]), and non-linear measures (CV1 and CV2 of the Poincaré plot) of 24-hour HRV in 94 healthy control subjects. Day-to-day reproducibility was evaluated on two occasions in 17 healthy subjects and 9 diabetic patients. The parameters of HRV were computed over time periods representing the day (6:00-24:00 hours), night (00:00-6:00 hours), and 24 hours in total. The results of all indexes, except for the LF/HF ratio and LF-NU, declined significantly with increasing age (p<0.05), but were independent of sex and BMI. The statistical, geometric, and non-linear measures (p<0.05), but not the frequency-domain parameters decreased significantly with increasing heart rate. Since the HRV data showed log normal distribution, log transformation was used to define the age-related lower limits of normal at the 2.5th centile. Intraindividual reproducibility was highest for the geometric measures. The nonlinear and statistical parameters also showed high reliability, except for the SNN50. The repeatability of the frequency domain measures was somewhat lower but still satisfactory. Reproducibility was lower in the diabetic than in the control group, higher during the day than during the night, and better than that reported previously for the AFTs. In conclusion, in healthy subjects the measures of 24-h HRV are not related to sex or BMI, but strongly dependent on age and heart rate, the latter except for the frequency domain measures. The majority of the HRV measures, in particular the geometric parameters, show a relatively high intraindividual reproducibility which underlines their suitability for the use in prospective studies.

Adult↗

PubMed1989

[Serum beta-carotene: a simple static laboratory parameter for the diagnosis of steatorrhea].

The value of serum beta-carotene concentration as an indicator of steatorrhoea was investigated in 50 patients with steatorrhoea (fecal fat greater than 7 g/day), 53 controls, and 22 patients with gastrointestinal disease without steatorrhoea. In the control group, beta-carotene concentrations were normally distributed when plotted logarithmically. The mean value was 131 micrograms/dl. The lower limit of normal, based on a 2-SD confidence interval, was 47 micrograms/dl. beta-Carotene concentrations and fecal fat excretion were correlated in a reciprocal, hyperbolic function (r = -0.66). Twenty-nine of the 50 patients with steatorrhoea had beta-carotene concentrations less than 47 micrograms/dl (sensitivity 58%; specificity 93%). Referring to an additional cut-off point of 100 micrograms/dl, beta-carotene concentration had a sensitivity of 88%. These data show that low plasma beta-carotene concentrations (less than 47 micrograms/dl) can be regarded a specific and useful indicator of steatorrhoea and thus obviate fecal fat analysis. Values greater than 47 micrograms/dl, however do not exclude steatorrhoea. Based on a two-step interpretation beta-carotene is thus both a useful screening test for steatorrhoea (with a cut-off point of 100 micrograms/dl) and, more important, a valid, simple, and clinically practical alternative for fecal fat analysis (if values are less than 47 micrograms/dl).

Carotenoids↗