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PubMed2002

New algorithms for processing and peak detection in liquid chromatography/mass spectrometry data.

Two new algorithms for automated processing of liquid chromatography/mass spectrometry (LC/MS) data are presented. These algorithms were developed from an analysis of the noise and artifact distribution in such data. The noise distribution was analyzed by preparing histograms of the signal intensity in LC/MS data. These histograms are well fit by a sum of two normal distributions in the log scale. One new algorithm, median filtering, provides increased performance compared to averaging adjacent scans in removing noise that is not normally distributed in the linear scale. Another new algorithm, vectorized peak detection, provides increased robustness with respect to variation in the noise and artifact distribution compared to methods based on determining an intensity threshold for the entire dataset. Vectorized peak detection also permits the incorporation of existing algorithms for peak detection in ion chromatograms and/or mass spectra. The application of these methods to LC/MS spectra of complex biological samples is described.

Algorithms↗

PubMed1991

[Morphological and functional characteristics of the heart in untreated hypertension].

UNLABELLED: To better define the different forms of hypertensive heart disease, we performed 2D guided M mode echo recording of the left ventricle (LV) and Doppler assessment of LV filling in 118 newly recognised (less than 1 year) and untreated hypertensive patients (mean age +/- SD: 49 +/- 10 years, 80 males, 38 females). All recordings were read "blindly". 86 patients underwent also 24 hours BP monitoring during daily routine. MAIN RESULTS: 1) The relative wall thickness (h/r) shows a normal distribution: mean = 0.39; SD = 0.08; 1st quartile = 0.33; 3rd = 0.43; 2) The septal/posterior wall ratio (ST/PWT) shows also a normal distribution: mean = 1.14; SD = 0.24; 1st quartile = 1; 3rd = 1.3; 3) Among patients with LVH (Devereux's criteria, n = 65) the 6 patients with h/r less than or equal to 0.33 are significantly different from the 18 patients with h/r greater than or equal to 0.43 for age (44 +/- 8 vs 51 +/- 10; p less than 0.03), casual (146 +/- 7 vs 166 +/- 13 mmHg; p less than 0.05) and ambulatory SBP (135 +/- 19 vs 146 +/- 16 mmHg; p less than 0.05), peak systolic stress (280 +/- 15 vs 187 +/- 31 Dynes/cm2; p less than 0.001) and E/A ratio (1.17 +/- 0.01 vs 0.94 +/- 0.27; p less than 0.05) but not for ponderal excess. 4) Patients with asymmetric LVH(ST/PWT greater than 1.3 in 22; greater than 1.5 in 10) are significantly different from patients with symmetric LVH for age (54 +/- 10 vs 47 +/- 10; p less than 0.03), diastolic diameter (51 +/- 5 vs 53 +/- 5 mm; p less than 0.02), ST (13.2 +/- 2.9 vs 10 +/- 1.9 mm; p less than 0.001) and PWT (8.9 +/- 1.5 vs 9.7 +/- 1.5 mm; p less than 0.02) but not for BP fractional shortening and LV filling. CONCLUSION: eccentric LVH may be found in young hypertensive patients with normal systolic function and LV filling despite high parietal stress; asymmetric LVH is more frequent in older patients in which LVH seems to develop rather on the septum than on free wall, independently of BP and without consequences on LV function.

Adult↗

PubMed2001

EUROPOEM, a predictive occupational exposure database for registration purposes of pesticides.

For registration of agricultural pesticides, the risks for humans, animals, and the environment must be determined. The risk assessment is based on an appraisal of the levels of exposure and the hazards of the active substance(s) in the plant protection product, that is, the agricultural pesticide. Funded by the European Commission (AIR3 CT93-1370), the EUROPOEM database has been developed by a group of experts, representing governments, industry, and academia. The currently available exposure database reflects exposure to operators (mixer/loaders and applicators). The EUROPOEM approach is based on a harmonized protocol for conduct of field studies of operator exposure (presently published as an Organization for Economic Cooperation and Development [OECD] Guidance Document) and a tiered approach to exposure and risk assessment. The database is constructed from exposure data obtained in representative field studies. These field studies are considered according to criteria reflecting the quality of documentation, study design, adequate methodology, number of replicates, and QA/QC elements, for use of the inhalation and dermal exposure data. The resulting exposure data were combined according to comparable use scenarios. From the resulting databases typical surrogate potential exposure values have been obtained, which are determined by their use for either acute or chronic health effects, and the size of the database. For large databases (over 50-100 data points), from many different field studies (10 or more), the 75th percentile is taken if the exposure is considered leading to chronic effects. For smaller databases, a more conservative 90th percentile is taken as surrogate value, or none at all for very small databases (15-20 or less data points from 3 or less different field studies). The choice for the 75th percentile is based on the assumed or observed lognormal distribution of the exposure data, as being the most relevant typical value for long-term effects, since the 75th percentile of log-normal distributions is nominally very similar to a calculated arithmetic mean (AM). The AM, as such however, is irrelevant for log-normal distributions.

Agriculture↗

PubMed1982

Mathematical aspects of the paternity index I = X/Y, especially in relation to the chance of non-exclusion of non-fathers.

In a previous paper the author mentioned some aspects of the paternity index I (= X/Y): Among false triplets the frequency of those with I equal to or higher than an (observed) I value of Ix is considerably lower than 1/Ix; among false triplets the mean value of I is equal to 1, and among non-excluded non-fathers it is equal to the inverse of the chance of non-exclusion; among true triplets the mean value of 1/I (= i) is equal to the chance of non-exclusion of non-fathers. In a statistical material rather strong deviations from some of these expectations were observed. In the present paper further characteristics of the distribution of I values were taken into consideration, and especially those that should hold if lnI would fit in with a normal distribution. It was supposed that with the aid of such a distribution the deviations mentioned above could be recognized as chance variability. It appears, however, that neither the logarithms of the paternity index, nor those of the zygosity index of twins (chosen as an analogous model that is more easily analysable than the paternity index) are really normally distributed. This, in turn, makes that estimates of probability of paternity, based on such a supposition, are of doubtful reliability. Besides it is concluded that also for other reasons other estimates than Essen-Möller's W (or I or i), as probability of first type errors, lead in practice to conclusions that are equally subdue to a priori suppositions as are W values and may be, in fact, much more erroneous than those. Special attention is paid to the statistical analysis of paternity studies with more than one alleged father, and it is concluded that in such cases the general formula that may be considered to be equivalent with Essen-Möller's formula for one-man paternity cases, i.e., W = X/(X + Y) or I/(I + 1), must be W1 = I1/(sigma I + n); W2 = I2/(sigma I + n) etc. and certainly not W1 = I1/(sigma I + 1); W2 = I2/(sigma + 1) etc.

Adult↗

PubMed1996

Commingling analysis of the distribution of a phenotype conditioned on two marker genotypes: application to plasma angiotensin-converting enzyme levels.

Commingling analysis is a statistical method for distinguishing between one (usually normal) distribution and a mixture of two or more distributions. It is used in genetic studies, since one mechanism giving rise to a mixture of distributions is the effect of a major gene. Plasma levels of angiotensin-converting enzyme (ACE) have been shown to be related to an insertion/deletion (I/D) polymorphism in the ACE gene. Recently, Cambien et al. [(1994) Circulation 90:669-676] used commingling analysis in a study of ACE, extending the method to condition on information about the I/D polymorphism in the gene. A further common polymorphism has been discovered recently by our group [Foy et al. (1995) Blood Coagulation Fibrinolysis 6:590] in the promoter region of the gene. In this paper we extend the method of commingling analysis to condition on two marker loci. The method is illustrated by application to plasma ACE levels in subjects for whom genetic information at both the I/D and promoter loci has been recorded. The results confirm strong evidence for a mixture of three normal distributions in preference to one or two, and also show that neither polymorphism is identical to a putative functional polymorphism. To assess the performance of the method, a simulation study was carried out. Parameters may be estimated more efficiently conditioning on two marker loci than on one or none, but this is not always the case if the underlying distributions are well separated. Conditioning on marker loci can increase the power to distinguish between alternative hypotheses of interest.

Adult↗

PubMed2003

No clear-cut evidence for cadmium-induced renal tubular dysfunction among over 10,000 women in the Japanese general population: a nationwide large-scale survey.

OBJECTIVE: To examine whether environmental exposure to cadmium has been inducing kidney dysfunction among middle-aged women in the general population in Japan. METHODS: This study was conducted in 2000 and 2001. Morning spot urine samples were collected from 10,753 women (mostly aged 35 to 60 years) in ten prefectures all over Japan (thus about 1,000 women per site). Urine samples were analyzed for cadmium (Cd-U), calcium (Ca-U), magnesium (Mg-U), zinc (Zn-U), alpha(1)- and beta(2)-microglobulins (alpha(1)- and beta(2)-MG-U). The urinary analyte concentrations were corrected for creatinine (cr) concentration (i.e., Ucr). The data thus obtained were subjected to statistical evaluation by chi-square test, ANOVA, multiple comparison test, and simple regression analysis (SRA) as well as multiple regression analysis (MRA) including logistic regression analysis (LRA). Log-normal distribution was assumed for Cd-Ucr, alpha(1)-MG-Ucr and beta(2)-MG-Ucr, whereas normal distribution was considered for age, Ca-Ucr, Mg-Ucr and Zn-Ucr. RESULTS: Geometric mean values (GM) of Cd-Ucr were distributed unevenly, depending on the sampling areas, with a grand GM of 1.3 microg/g cr, the highest (3.2 microg/g cr) and lowest GM values(0.8 microg/g cr) being significantly different from GMs of other areas. Correlation matrix analysis with subjects of all ages showed that log alpha(1)-MG-Ucr and log beta(2)-MG-Ucr correlated significantly (r=0.272 and 0.202, respectively) with log Cd-Ucr, but they correlated also with age (r=0.280 and 0.213, respectively). The same analysis with the two selected age groups (41-50 and 51-60 years), however, failed to show close correlation of alpha(1)-MG-Ucr and log beta(2)-MG-Ucr with Cd-Ucr. Both MRA and LRA indicated that age was a confounding factor in the evaluation of the effect of Cd-U on the two MG levels. Whereas the LRA with the all-age group showed a positive influence of log Cd-Ucr on log alpha(1)-MG-Ucr and log beta(2)-MG-Ucr, such effect disappeared in parallel with the disappearance of age effects when LRA was conducted with the two selected age groups. An exceptional observation was the influence of log Cd-Ucr on log alpha(1)-MG-Ucr (but not on log beta(2)-MG-Ucr) in LRA when a cut-off value of 5.00 mg for alpha(1)-MG-U/g cr was applied. Comparison between the low and high Cd-U groups showed that both alpha(1)-MG-Ucr and beta(2)-MG-Ucr were higher in the high Cd-U groups, but prevalence of cases with alpha(1)-MG-Ucr and beta(2)-MG-Ucr in excess of the cut-off values did not differ between the two groups except when a cut-off value of 5.00 mg/g cr was employed for alpha(1)-MG-U. CONCLUSIONS: In over-all evaluation, no clear-cut evidence was obtained in the present study to show that environmental exposure to Cd has induced tubule dysfunction among middle-aged women in the general population in Japan. It might be the case, however, that an increase in alpha(1)-MG-U was associated with Cd exposure. In this sense, it is apparently desirable from public health viewpoints to make further efforts to reduce the intensity of the general population's exposure to environmental Cd.

Adult↗

PubMed1989

Resistance development to fluoroquinolones in Europe.

We did not observe an increase in quinolone-resistant strains in recent years despite a dramatic increase in drug usage. P. aeruginosa strains should be carefully monitored in the future since a trend to increased MICs seems obvious. Epidemiologic data on resistance have to be evaluated carefully, and special interest must be focused on the breakpoint in relation to the normal distribution of MICs. Conclusions can be drawn only if the increased numbers of strains are clearly separated from the normal distribution.

4-Quinolones↗

PubMed2026

Flap Versus Tunneling for Horizontal Ridge Augmentation With FDBA and i-PRF: A Randomized Controlled Clinical Trial.

AIM: This study evaluated the efficacy of conventional flap and tunneling techniques for horizontal alveolar ridge augmentation using freeze-dried bone allograft (FDBA) particles combined with injectable platelet-rich fibrin (i-PRF). MATERIALS AND METHODS: Forty-five patients were randomly allocated to one of three groups (n = 15 each): conventional flap (CF), tunneling with membrane (TM), or tunneling without membrane (TnM). Preoperative ridge width was measured via cone beam computed tomography (CBCT). All augmentation procedures incorporated FDBA and i-PRF; an absorbable collagen membrane was applied in the CF and TM groups. Follow-up assessments, including CBCT imaging and histomorphometric analysis, were conducted 6 months postoperatively. For normally distributed data, ANOVA with Tukey's post hoc test and paired samples t-test were applied. Non-normally distributed data were analyzed using Kruskal-Wallis, Mann-Whitney U, and Wilcoxon signed-rank tests. RESULTS: Statistical analysis was performed on 43 patients. All groups demonstrated an increase in ridge width after 6 months. At the 2 mm level, the mean width gain was 1.28 mm (95% CI: 0.17 to 2.40) in the TM group, 2.85 mm (95% CI: 1.80 to 3.89) in the TnM group, and 1.95 mm (95% CI: 1.07 to 2.83) in the CF group. However, statistical analysis revealed no significant intergroup variation (p > 0.05). Histomorphometric assessments similarly demonstrated comparable outcomes across all groups, with no statistically significant differences observed (p > 0.05). CONCLUSION: Within the limitations of this study, the tunneling technique, regardless of membrane use, appears to be a clinically viable alternative to the conventional flap method for horizontal alveolar ridge augmentation. However, further studies with longer follow-up periods are required to substantiate these findings. TRIAL REGISTRATION: irct.behdasht.gov.ir identifier: IRCT 20101204005305N21.

Humans↗

PubMed1983

Heat distribution over normal and abnormal joints: thermal pattern and quantification.

We have identified regular thermal patterns over normal knee, ankle, and elbow joints and demonstrate how synovitis affecting these joints may be identified by alteration or loss of the thermal pattern. Sixty healthy volunteers were thermographed on a total of 190 occasions, and 614 out of 618 joints conformed to the normal thermal pattern. Eighty-five patients with synovitis of at least one of the specified joints were thermographed on a total of 339 occasions, and 322 out of 1362 thermograms were abnormal. No joint with clinical evidence of synovitis had a normal thermal pattern. As temperature-based parameters have been found to show marked diurnal variation and relative frequency distributions do not have this drawback, we suggest that quantification of synovitis by thermography should in future be based on abnormalities of thermal pattern rather than absolute skin temperature values.

Adolescent↗

PubMed1978

Changes in numbers and heparin content of peritoneal fluid mast cells of growing rats measured by flow cytofluorometry.

A cytofluorometric method, based on berberine staining of mast cell heparin, was used for flow cytofluorometric counting and heparin quantitation of mast cells in crude peritoneal suspensions of growing rats. The automatic flow cytofluorometric counting of mast cells correlated well with hemocytometer cell counts. The mean mast cell heparin content obtained by flow cytofluorometry showed good agreement with such obtained by cytofluorometry of microscopically identified mast cells. The number of peritoneal mast cells and the mean mast cell heparin content was found to increase as the animals grew older. The results of the microscope fluorometric measurements suggested that the heparin content was normally distributed within mast cell populations of both young and old rats. However, the heparin distributions obtained by flow cytofluorometry were often positively skewed but did not fulfill the condition of the log-normal distribution.

Aging↗

PubMed1979

Interrelation of the pituitary-thyroid system at birth in man.

Samples of cord blood derived from 105 normal babies after uncomplicated deliveries were assayed for thyroxine (T4), tri-iodothyronine (T3), reverse tri-iodothyronine (rT3), thyroxine-binding globulin (TBG) and thyrotrophin (TSH). The values for T3, rT3 and TSH were log-normally distributed (geometric means 0.62 nmol/l, 3.28 nmol/l and 10.9 mu./l respectively) and those for T4 and TBG were normally distributed (means 126 nmol/l and 13.7 mg/l), The data were systematically analysed and no evidence was obtained to suggest that the concentration of TSH, which varied widely, was regulated by any of the thyroid hormones alone or in combination. There was a direct relation between the concentrations of T4 and T3 in the cord blood at birth but not between either of these and rT3. There is thus no evidence of a functional interdependence of the hypothalamic-pituitary-thyroid system in man at birth.

Fetal Blood↗

PubMed1993

Bronchoalveolar lavage and lung biopsy in rheumatoid arthritis. In vivo effects of disease modifying antirheumatic drugs.

Bronchoalveolar lavage (BAL) and histology of transbronchial forceps biopsy was performed in 59 patients with rheumatoid arthritis (RA) to evaluate the in vivo effects of disease modifying drugs (DMARD). All patients had no clinical pulmonary symptoms and there was no evidence of drug induced alveolitis. Patients were divided into 5 subgroups according to drug treatment: 9 patients taking chloroquine, 15 patients gold, 8 patients penicillamine, 8 patients methotrexate (MTX) and 19 patients not taking DMARD. Duration of DMARD regimen was more than 3 months. No patient was treated with corticosteroids. BAL results revealed an increased percentage of lymphocytes and a diminished proportion of alveolar macrophages in patients treated with gold, penicillamine, MTX and no DMARD. In contrast, patients receiving chloroquine had a normal distribution of lymphocytes and macrophages as seen in a control group of 15 persons. Patients taking MTX showed a normal distribution of T and B lymphocytes and DR positive cells, whereas patients receiving chloroquine, gold, or penicillamine had an elevated proportion of T lymphocytes and DR positive cells and a diminished percentage of B lymphocytes. The latter was also observed in patients not taking DMARD. The percentage of natural killer cells was significantly elevated only in the penicillamine group. Patients receiving gold had higher absolute values of CD3, CD4 and DR positive cells. Abnormal lung histology was associated with an increased percentage of lymphocytes and with higher DR positive cells in BAL. Patients not receiving DMARD had a significantly higher percentage (42.1%) of abnormal histologic features of lung tissue than patients receiving DMARD (17.5%).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗

PubMed1986

[Does the determination of basal TSH level replace the TRH test?].

With the help of the newly developed "supersensitive" assays for thyrotropin it is possible to determine concentrations down to 0.03 mU/l. Patients with a manifest hyperthyroidism show, as a rule, very low TSH levels and they react not at all or only very weakly to TRH stimulation. Therefore, various authors have claimed that estimation of the basal TSH level is sufficient as a screening test for the exclusion of a hyperthyroidism. To check the reliability of this statement we determined the reference interval of the parameter "basal TSH". It is a log-normal distribution; the reference interval of healthy people (95. percentile) is 0.25-4.0 mU/l. The TSH response to TRH stimulation also follows a log-normal distribution, the reference interval being 3.0-20 mU/l. There is a poor correlation between both parameters (r = 0.83). Histograms of populations with reduced, normal, or increased reactivity to TRH stimulation show broad overlapping zones. A valid prediction (with a plausibility greater than 90%) of the TSH response to TRH stimulation is therefore possible in the extreme ranges only (less than 0.2 mU/l for reduced, greater than 5 mU/l for increased reactivity respectively). In between there is a wide "gray zone", where reliable prediction is not possible on the basis of laboratory data only (without clinical findings).

Adult↗

PubMed2003

Evaluation of the effect of flights in supersonic fighters on sinus rhythm variability parameters.

Heart rate variability is a widely used method to evaluate vagal and sympathetic influences on the heart. The purpose of this study was to assess the relationship of autonomic nervous system components' interaction in supersonic fighter pilots by means of a sinus rhythm variability analysis. The following frequency domain parameters were analyzed: low-frequency (LF) power spectral of 0.05 to 0.15 Hz (ms2); high-frequency (HF) power spectral of 0.15 to 0.45 Hz (ms2); LF and HF power spectral index; total spectral power (HF + LF); percent, LF distribution in total spectral power; percent HF, HF distribution in total spectral power; and an average heart rate per minute. The study comprised 30 healthy military pilots (age, 24-48 years) in whom heart rate variability parameters were determined 10 to 12 minutes before take off, 10 to 12 minutes after four successive flights, and 1, 2, and 12 to 16 hours after completing the flights. The control group was comprised of 20 healthy nonpilots (age, 24-49 years). The statistical significance was estimated by means of the following methods: Student's t test for normal distribution and a rank test for the non-normal one (between the groups of the same subjects); and the Cochran-Cox test for normal distribution and the Wilcoxon test for the non-normal one (between the groups of different subjects). Higher activity of sympathetic components of the autonomic nervous system was shown in pilots in the course of the first examination before flights as compared with the controls (higher LF, LF/HF, percent LF). Predominance of the sympathetic nervous system in pilots might reflect adaptation to repeated short-term exposures to high values of accelerations acting in head-leg axis.

Adult↗

PubMed1975

Biostatics of the tibial shaft.

In all, 56 tibiae from Lapps and 56 tibiae from Norwegians have been studied. These ethnic groups represent different weight bearing situations. Only measurements referring to the diaphysis are presented. The bones are studied in the AP and ML planes and at different transverse sections. The material is analyzed statistically. The distribution form is examined. Chiefly positive skewness occurs. Platykurtosis is found twice as often as leptokurtosis. A differentiated pattern of distribution seems to be the case regarding measurements in the lower extremities. This corresponds to the influence of variable hereditary and external factors. Divergencies from standard normal distribution is compared with differences between groups. In some cases differences are influenced by platykurtosis and skewness. Divergence from standard normal distribution could not be traced back to measuring errors, special features of the bone or special sex characteristics. The divergencies are not supposed to affect the results to any noteworthy extent. Female Lapps show small variances, female Norwegians great variances. In linear variables Lapps generally show smaller values than Norwegians, females smaller values than males. Regarding linear measurements, sex differences are a little more marked than differences between the two ethnic groups. The opposite is the case regarding the angular measurements and the indices. The sex differences in linear measurements are smaller in Lapps than in Norwegians. The opposite is the case regarding the length of the bone. In Lapps, angular measurements and indices show no significant sex differences. Regarding linear measurements, differences between the ethnic groups are mostly due to differences between the males. The opposite may be said about the indicnes. The variations of the tibia recorded and discussed in the present paper are the results of mechanical factors influencing the basic processes in functional bone remodelling. The periosteal ossification is particularly involved in the dimensions of the shaft, the epiphyseal cartilage in the length dimensions. Particularly important is the relation between the weight bearing line and the diaphysial axis of the bone, and the muscles activated by variation is this relation.

Adult↗

PubMed1993

Tissue-specific lipoprotein lipase: relationships to body composition and body fat distribution in normal weight humans.

Twenty-six normal weight subjects (22 female, 4 male) were studied to determine the relationships of fasting levels of lipoprotein lipase in gluteal adipose tissue (ATLPL) and skeletal muscle (SMLPL) to body composition and body fat distribution. No relationship was found between fasting gluteal ATLPL and percent (%) body fat. There was, however, an inverse relationship between fasting SMLPL (from the vastus lateralis) and %body fat (p=0.005). A strong inverse correlation was also seen between fasting ATLPL and waist/hip ratio (p=0.0006), a measurement of body fat distribution. These relationships existed with or without the male subjects included. The tissue-specific relationships of lipoprotein lipase to body composition and body fat distribution could relate to the development of obesity or the maintenance of normal body weight by the effects of the lipase on the partitioning of lipoprotein triglyceride fatty acids.

Adipose Tissue↗

PubMed1984

Admixture analysis of plasma cholesterol levels in a Jewish population sample in Jerusalem.

The frequency distribution of total plasma cholesterol levels (TC) in 17-year-old Jerusalem youngsters and their parents (n = 6,170) was examined for evidence of admixture of normal distributions. Probability plots indicated bimodality of age-adjusted TC in both sexes. Using a maximum likelihood procedure, two normal distributions fitted the age- and sex-adjusted data significantly better than 1, with 0.9% males and 1.2% females coming from a lower distribution 2-3 standard deviations below the major mode and 0.2% males and 1.1% females belonging to the higher distribution. These results suggest that single genes may determine high as well as low cholesterol levels, but are open to other interpretations, and thus require confirmation by segregation analysis. Jews originating from Europe showed the highest TC levels followed by those from Israel, Asia, and Africa. Adjustment of TC for ethnicity did not alter the above estimates. Analysis of bimodality within countries of origin showed greater separation of the distributions in Asian and Israeli origin groups than in European and North African groups, in whom there was less evidence for admixture.

Adolescent↗

PubMed2004

Evaluation of methodologies for small area life expectancy estimation.

STUDY OBJECTIVE: To evaluate methods for calculating life expectancy in small areas, for example, English electoral wards. DESIGN: The Monte Carlo method was used to simulate the distribution of life expectancy (and its standard error) estimates for 10 alternative life table models. The models were combinations of Chiang or Silcocks methodology, 5 or 10 year age intervals, and a final age interval of 85+, 90+, or 95+. SETTING: A hypothetical small area experiencing the population age structure and age specific mortality rates of English men 1998-2000. PARTICIPANTS: Routine mortality and population statistics for England. MAIN RESULTS: Silcocks and Chiang based models gave similar estimates of life expectancy and its standard error. For all models, life expectancy was increasingly overestimated as the simulated population size decreased. The degree of overestimation depended largely on the final age interval chosen. Life expectancy estimates of small populations are normally distributed. The standard error estimates are normally distributed for large populations but become increasingly skewed as the population size decreases. Substitution methods to compensate for the effect of zero death counts on the standard error estimate did not improve the estimate. CONCLUSIONS: It is recommended that a population years at risk of 5000 is a reasonable point above which life expectancy calculations can be performed with reasonable confidence. Implications are discussed. Within the UK, the Chiang methodology and a five year life table to 85+ is recommended, with no adjustments to age specific death counts of zero.

Aged↗