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PubMedDate not supplied

[Fluctuations affecting the measurement of microfilaremia (author's transl)].

A statistical analysis was conducted, in order to compare the variations in values of a) blood samples obtained with several finger-pricks from the same individual in a short period of time, and b) blood samples obtained from the same finger-puncture. No significant difference was observed: both groups seem to follow a negative binomial distribution, the exponent of which is not dependent on the microfilarial count average. This common exponent is roughly equal to the volume of the blood sample, expressed in cmm.

Blood Specimen Collection↗
PubMedDate not supplied

[The filaria Dipetalonema dessetae: phenomena of regulation and parasite yield in the Aedes vector].

Numerical observations were made on the various steps of the cycle of Dipetalonema dessetae in Aedes aegypti: -- ingestion of microfilariae: the numbers of the ingested microfilariae correspond to a negative binomial distribution, but the over-dispersion is less important than in the Bancroft's filaria as observed by Pichon; in this last case the microfilariae are thicker and thus are more slowed in the capillari; -- crossing of the stomach wall: the "limitation" is caused by a precociously established stomacal barrier (2nd hour); however, this barrier is not perfect and allows some microfilariae to infiltrate; -- larval development and migration towards the head: in the well fed mosquitoes, all the microfilariae in the hemocoel reach the infective stage, but less rapidly in the heavily infected mosquitoes; 50 per cent of the microfilariae migrate towards the head, not depending with the level of infection. In this couple filaria-vector, the regulation of the transmission is depending nearly exclusively with the stomacal "limitation" and secondarily with different speeds of the development. The feeding of the mosquito -- preimago or adult -- is an essential factor for vector efficiency.

Adipose Tissue↗
PubMed1994

On the use of the quasi-likelihood method in teratological experiments.

This paper concerns the impact of litter effects on the inference of dose-response relationships in teratological experiments with binary response. Kupper et al. (1986, Biometrics 42, 85-98) concluded that when intra-litter correlations are dose-dependent, the use of a common intra-litter correlation likelihood based on the beta-binomial distribution could lead to severe bias in estimation of the parameter beta, which characterizes the dose-response relationship. We show here that the problems of bias and coverage probability for beta could still be substantial when one uses the likelihood with heterogeneous intra-litter correlations. We then examine through a simulation study the performance of the quasi-likelihood method (Wedderburn, 1974, Biometrika 61, 439-447) and recommend that this method with a common intra-litter correlation parameter be used when the number of litters is small or modest.

Analysis of Variance↗
PubMed1993

[Application of HBV gene subtyping method in study on familial transmission].

A cross-section epidemiological study for hepatitis B was conducted in the population of a village in Hebei Province. The prevalence rate of HBsAg was 3.75% (22/586), and HBV infection rate, 27.65% (162/586), without significant difference between males and females; and increasing with age. This village belongs to a low HBV incidence region in China. This phenomenon might possibly be related to the characteristic of the population (mostly blood donors) and high incidence of HCV (prevalence rate of anti-HCV was 10.31%, 59/572). The anti-HBc and overall HBV infection rate showed family clustering by binomial distribution analysis. The family clustering of HBV infection resulted mainly from the transmission from parents to their children and among the children. The overall positivity rate of HBV DNA was 24.77% (27/109), and the majority of the family members belonged to the same subtypes (72.22%). On the basis of HBV subtyping, familial transmission of HBV was classified into six types, ie. generational, horizontal, recessive, intra- and extra-familial, non-familial and undetermined ones.

Adolescent↗
PubMed1993

Prediction of postoperative visual acuity in patients with total glaucomatous cupping using the Potential Acuity Meter and automated perimetry.

We evaluated the effectiveness of using the Potential Acuity Meter (PAM) and automated perimetry to predict postoperative vision in 30 advanced glaucoma patients following combined cataract extraction and trabeculectomy. Using the binomial distribution at alpha = 0.05, PAM and automated perimetry individually were significantly useful in predicting postoperative vision of 20/40 or better. Automated perimetry, but not PAM, was useful in predicting worse than 20/40 vision. Used together, automated perimetry and PAM testing were significantly useful in predicting vision worse or better than 20/40.

Aged↗
PubMedDate not supplied

[Degree of aggregation of Ascaris lumbricoides according to age groups after a massive antihelmilthic intervention].

OBJECTIVE: The degree of aggregation is determined for the whole population and for different age-specific strata and is used for assessing the reinfection rate after a mass antihelminthic chemotherapeutic intervention. MATERIAL AND METHODS: The degree of aggregation of Ascaris lumbricoides is derived from prevalence and intensity of infection date obtained from an epidemiological study of ascariasis carried out in Coatzacoalcos, Veracruz, México by means of maximum likelihood estimation of the negative binomial distribution. RESULTS: The results show that the distribution of the parasite for the whole population differs from the distribution of the parasite within each age-specific stratum; the reinfection rate is not uniform, the dynamics of the host-parasite association exhibits a clear destabilization of its endemic equilibrium after a first round of mass treatment. CONCLUSIONS: It is suggested that the aggregation among the different age-groups is highly variable and hence the infection and reinfection rates are heterogeneous with regard to age; these states of the host-parasite system are transient. Given the heterogeneity of the infection, the selective treatment seems to be the most adequate strategy to diminish helminth infection rates.

Age Distribution↗
PubMed1997

Prevalence of infection, mean worm burden and degree of worm aggregation as determinants of prevalence of disease due to intestinal helminths.

Theoretical predictions of disease prevalence due to helminth infections based upon a simple probabilistic model which considers the infection prevalence, the mean worm burden and the degree of worm aggregation are presented. A numerical reappraisal of the likely estimates of the degree of aggregation based upon maximum likelihood estimates of the negative binomial distribution is presented. The prevalence of disease shows a positive relationship with the mean worm burden. This association is hyperbolic when helminth parasites are severely aggregated but is s-shaped when helminth parasites tend to be overdispersed. The prevalence of disease decreases with the degree of worm aggregation when the values of the mean intensity are low; as the mean intensity increases this association becomes positive. The relationship between prevalence of disease and prevalence of infection is hyperbolic for severe degrees of parasite aggregation and is s-shaped for intermediate degrees of aggregation. However, if the mean intensity is low and the degree of aggregation is high there could be a negative relationship between the prevalence of disease and the prevalence of infection. The presence of disease due to helminth parasites is feasible for determined ranges of values of the infection prevalence, mean intensity and the degree of worm clumping.

Animals↗
PubMed1996

[Laterality in twins].

The literature on twins and laterality is reviewed: Both monozygotic (MZ) and dizygotic twins (DZ) show a low concordance in all functional and morphological asymmetries. The proportions of R-R, R-L and L-L pairs in MZ twins and in DZ twins are in binomial distribution. The incidence of left-handedness is the same in MZ twins and DZ twins, but higher than in singletons. Other laterality signs do not show this tendency. The whole issue of twinning is as yet unresolved, yet it is clear already that no simple genetic model for the inheritance can be applied. The present review discusses three genetic models and associated problems with each. The overall tendency to a higher rate of left-handedness in twins could be due to such pathological factors (associated with twinning) as intrauterine crowding and perinatal stress, but is not due to so-called "mirror imaging"-phenomena in twins.

Functional Laterality↗
PubMed1998

Investigation of haematophagous arthropods for borreliae--summarized data, 1988-1996.

Blood-sucking arthropods, collected in South Moravia, Czech Republic, were examined by darkfield microscopy for borreliae from 1988 to 1996. Among host-seeking ixodid ticks (8481 Ixodes ricinus (L.), 372 Dermacentor reticulatus (Fabr.), 167 Haemaphysalis concinna Koch), borreliae were only observed in adult (23.2%), nymphal (17.2%) and larval (6.3%) I. ricinus. The prevalence of borreliae in I. ricinus did not vary considerably among habitats except for lower values in agroecosystems, xerothermic oak woods and grasslands. The frequency of intensity of spirochaetal infection (log10 counts of borreliae per tick) in I. ricinus approximated the negative binomial distribution. The proportions of host-seeking female and nymphal ticks containing > 100 borreliae were 5.0% and 1.7%, respectively. Among preimaginal ticks (749 I. ricinus, 222 D. reticulatus, 82 H. concinna) parasitizing free-living forest birds and small mammals, borreliae were detected in 6.1% of larval and 10.3% of nymphal I. ricinus, and in one larval H. concinna; 3.2% of the birds and 19.4% of the mammals carried infected ticks. Among 3464 female mosquitoes (Culicidae) of 6 species, 4.1% contained spirochaetes: 1.4% of Aedes vexans Meig., 1.3% of A. cantans (Meig.), 2.2% of A. sticticus (Meig.), 2.2% of Culex pipiens pipiens L. and 5.9% of C. p. molestus Forskal. Borreliae were also detected in 8.4% of 142 fleas (Siphonaptera, largely Ctenophthalmus agyrtes Heller and Hystrichopsylla talpae Curtis) collected from small mammals. Twelve isolates of B. burgdorferi sensu lato have been identified to genospecies: 6 strains from I. ricinus (4 Borrelia garinii Baranton et al., 1 B. afzelii Canica et al. and 1 B. lusitaniae Le Fleche et al.), 1 strain from A. vexans (B. afzelii), 2 strains from C. agyrtes (B. afzelii), and 3 strains from host rodents (B. afzelii).

Animals↗
PubMed1998

[Arm folding--an overview].

The literature concerning arm folding is reveiwed. This analysis could be based on 121 populations. In addition to this the paper discusses incidence, sex, age differences and genetical problems including twinning. The incidence of left arm folding ranges from 20% to 65% (mean value 54%). The review shows a predominance of the left-type in Europe. Age and sex differences are only small. Between arm folding and handedness no relationship could be found, and only a very weak one between arm folding and hand clasping. 13 authors examined arm folding in families, and 2 in twins. The family data suggest that arm folding may be under a certain genetic control, yet it is clear that no simple genetic model concerning the inheritance can be assumed. Monozygotic as well as dizygotic twins show a low rate of concordance, and the frequencies of R-R, R-L and L-L pairs in monozygotic and dizygotic twins show a binomial distribution.

Female↗
PubMed2006

Interdependence and distribution of subclinical mastitis and intramammary infection among udder quarters in dairy cattle.

The objective of the present study was to determine the distribution of subclincial mastitis and intramammary infection (IMI) across udder quarters and to quantify, if any, the level of interdependence between quarters. Subclinical mastitis was defined as an udder quarter somatic cell count of > or =250,000. Intramammary infection was defined as the presence of pathogens in an udder quarter. The data used in the analyses consisted 6577 test-day records from 2034 lactations with observations on subclinical mastitis and 8428 test-day records from 2575 lactations with observations on IMI; each test-day record consisted data on all four udder quarters. Records were from animals on three research herds in southern Ireland. Observed distributions of IMI were compared to expected distributions, estimated using a binomial probability distribution, assuming independence among quarters. Generally, the observed frequencies deviated significantly from the expected frequencies, indicating some level of interdependence between quarters. Intraclass correlations were estimated from a mixed model including cow and test-day record nested within cow as random effects; fixed effects in the model included herd, year of calving, month of calving, parity, days in milk at sampling and interactions. Intraclass correlations within test-day record ranged from 0.14 to 0.50 for subclinical mastitis and from 0.02 to 0.40 for IMI. Thus, substantial interdependence between quarters exists which should be accounted for when analysing data from experiments across udder quarters. Failure to do so may result in incorrect inferences from statistical tests.

Animals↗
PubMed1984

The effects of sample size on reticulocyte counting and stool examination. The binomial and poisson distributions in laboratory medicine.

In tests that involve counting or searching for discrete objects, clinical laboratory specimens that are too small produce insensitive and imprecise test results. We found that ten of 57 surveyed New England hospital laboratories examine less than a 50-mg stool sample for parasite eggs; they are, therefore, unlikely to detect infections characterized by low concentrations of eggs in stool. Conversely, all 57 laboratories use the traditional, appropriate sample size of at least 1,000 RBCs for reticulocyte counting. In this report, we discuss theoretical and practical considerations in small sample testing.

Blood Cell Count↗
PubMed1989

Analysing rearrangement breakpoint distributions by means of binomial confidence intervals.

Non-randomness in the distribution of rearrangement breakpoints can be assessed by means of a binomial probability model. Using the binomial model, we compute confidence intervals for the observed number of breakpoints in chromosome bands and use these confidence intervals to test for non-randomness in a set of 452 constitutional rearrangement breakpoints. This method is useful because it describes the observed data and is not dependent on comparison with a pre-existing hypothesis regarding the distribution.

Biometry↗
PubMed1995

Basic models for disease occurrence in epidemiology.

BACKGROUND: One of the epidemiologist's most basic tasks is estimation of disease occurrence. To perform this task, the epidemiologist frequently models variability in disease occurrence using one of three distributions--the binomial, the Poisson or the exponential distribution. Although epidemiologists often use them and their properties appear in standard texts, we know of no text or review that compares and contrasts epidemiological application of these distributions. METHODS: In this commentary, we discuss these three basic distributions. We note key assumptions as well as limitations, and compare results from analyses based on each distribution. RESULTS AND CONCLUSIONS: We illustrate that the three distributions, although superficially different, often lead to similar results. We argue that epidemiologists should often obtain similar results regardless of which distribution they use. We also point out that application of all three distributions can be inappropriate if assumptions of independence or homogeneity of risks fail to hold. Finally, we briefly review how these basic distributions can be used to justify use of other distributions, such as the Gaussian distribution, for studying disease-exposure associations.

Binomial Distribution↗
PubMed1977

Consultation frequencies in general practice.

Some models of the process by which individuals seek medical care suggest the negative binomial as the underlying distribution of the frequencies of consultations in a given practice. Data from the 1970-71 National Morbidity Survey of General Practice are used to test these competing models. It is shown that the negative binomial distribution successfully fits consultation frequencies in aggregate and in subdivisions according to age, sex, and duration of registration. In this article is is assumed that the consultation process has two components: the patient's decision to visit his doctor for a new illness and the follow-up visits that results from this new problem. Supplementing previous evidence that the distribution of episodes of new illnesses follows a negative binomial distribution, this article shows that consultation frequencies among individuals presenting with one new illness also follow a negative binomial distribution. A unifying model is required to synthesize these findings.

Adolescent↗