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PubMed1999

[Biological inter- and intra-individual variations of serum immunochemical constituents and their allowable limits of analytical error].

The biological inter- and intra-individual variations of serum immunochemical constituents were estimated by the analysis of variance. Twelve samples taken at weekly intervals were analyzed for 22 healthy individuals. As for immunoglobulin (Ig) G, IgA, IgM, IgE, C-reactive protein, anti-streptolysin O, alpha-fetoprotein, complement component 3 and 4, and ferritin, the intra-individual variations (with coefficient of variations (CVs) ranging from 4.8% to 51.7%) were smaller than the inter-individual variations (with CVs ranging from 14.6% to 107.6%). The values for carcinoembryonic antigen (with CVs of inter- and intra-individual variation being 31.6% and 39.6%, respectively) and beta 2-microglobulin (with CVs of inter- and intra-individual variation being 14.4% and 13.1%, respectively) were similar. The biological variations of serum immunochemical constituents, examined in this study, were larger than those of serum chemical constituents. Based on our data, we propose allowable limits of analytical error, which is less than one-half of the average intra-individual variation for evaluation of imprecision and is less than one-quarter of the inter- plus intra-individual variation for evaluation of inaccuracy.

Analysis of Variance↗

PubMed1999

[Intra- and inter-individual variations in diets of the middle-aged and the elderly].

This study was conducted to examine intra- and inter-individual variations in diets of the middle-aged and the elderly (40 years or older, 46 men and 42 women). The coefficients of variations for intakes of nutrients and food groups were computed from four 4-day weighed dietary records performed at 3-month intervals from June 1996. The results were as follows: a) The highest intra-individual variation (%) for nutrient intake was observed in retinol (men 293.5, women 283.8) and the lowest in carbohydrate (men 17.7, women 22.1). b) The highest inter-individual variation (%) was found in retinol (58.2) in men, and in carotene (56.7) in women. The lowest inter-individual variation (%) was observed in magnesium (17.0) in men, and in carbohydrate (14.4) in women. c) Nuts and seeds showed the highest intra-individual variation (%) for food group intake (men 291.5, women 391.8), while rice presented the lowest (men 30.5, women 38.9). d) The highest inter-individual variation for food group intake (%) was seen in milk and dairy products (111.7) in men and in alcoholic beverages (162.3) in women. The lowest inter-individual variation was observed in potatoes and starches (20.7) in men and in pulses (26.0) in women. e) The number of days necessary to estimate true average nutrient intake was much longer for such vitamins as retinol and carotene (over 50 days) than for macronutrients (3-5 days) except for fat. More than one year was required to estimate intake of nuts and seeds in both sexes and alcoholic beverages or seaweeds in women, whereas only 9-15 days for intake of rice. In conclusion, energy, protein and carbohydrate can be estimated by short-period dietary recalls or records, since their intra-individual variations were relatively small. On the other hand, many days, were found to be required to estimate usual dietary intake of such vitamins as retinol or carotene and that of each food group except for rice. It would therefore be very difficult to estimate usual intake of these nutrients and food groups by short-period dietary recalls or records.

Diet↗

PubMed2000

Comparing methods for estimating the variation of risks of cancer between small areas.

BACKGROUND: Analysing the geographical variation of cancer incidence is an important issue in epidemiological research. It might suggest new aetiologic hypotheses, provide guidelines for the design of new surveys and give ideas for preventive campaigns. METHODS: Four different methods for estimating the variation of cancer risks between small areas and three homogeneity tests were evaluated by simulation. In three of the methods the systematic variation of the relative risks (RR) was estimated by subtracting the expected Poisson variation from the total variation. The last method assumes that RR are gamma distributed and the maximum likelihood estimate (MLH) of the systematic variation parameter is calculated. A likelihood ratio test (LRT) of heterogeneity of RR based on this method is also evaluated, and compared with an ordinary chi2 test and the Potthoff and Whittinghill test (P&W). RESULTS: For most of the simulated data-sets, the estimates obtained by MLH are most precise, even if the assumption of gamma distribution of RR is violated. The LRT and P&W tests of homogeneity are also shown to perform better than the chi2 test. Most of the real cancer data-sets exhibited at least some geographical variation. Cancer of the lung, melanoma and other skin cancers, and cancers of the urinary bladder, pancreas and stomach, have the highest systematic variation. DISCUSSION: The study suggests that likelihood-based approaches are suitable, both for estimating the variation between small areas and for testing the null hypothesis of equal RR. Such geographical analyses might suggest new aetiological hypothesis.

Chi-Square Distribution↗

PubMed2002

Spatial variations of Pb in the vertical zone of the soil-plant system in the Changbai Mountain National Nature Reserve.

The characteristics of vertical and horizontal variations of lead element(Pb) in soil-plant system of vertical zone in Changbai Mountain National Nature Reserve(CNNR) were studied. The results showed that Pb concentrations in soils of vertical zone are all above 25 mg/kg, and the average Pb concentration of each soil zone negatively correlates its degree of variation, i.e. brown coniferous forest soil zone has the lowest average Pb concentration of four soil zones, and the highest horizontal variation; however, mountain soddy forest soil has the highest average Pb concentration, and the lowest horizontal variation; the average concentration of plant Pb of each plant zone is lower than the worldwide average level of Pb in plant(Clarke), respectively, and plant Pb content order is consistent with soil Pb content order, but their horizontal variations are different from those in soil zones, the variation of mountain tundra forest zone is highest, but Betula ermanii forest zone the lowest. Vertical variation of plant Pb is obviously higher than that in soils with variation coefficient of 89.76%; the enrichment capability of plant for Pb is depended on the plant types and the different organs of plant; parent material and parent rock, pH values, soil organic matter and soil particle fraction etc. are the main factors influencing variations of Pb content in soil-plant system of vertical zone in CNNR.

Betula↗

PubMed2003

Seasonal variation in meningococcal disease in Denmark: relation to age and meningococcal phenotype.

Seasonal variation has been shown in meningococcal disease (MD), but it is not known whether seasonal variation depends on age, gender and meningococcal phenotype. Based on complete registration of MD in North Jutland County, Denmark, during 1980-1999 (n = 413 cases), a Poisson regression model of a sinusoidal form was used to examine: (i) whether the seasonal variation in MD follows a sinusoidal pattern; (ii) the magnitude of seasonal variation in MD; and (iii) whether seasonal variation is related to age and gender and meningococcal phenotype. The peak-to-trough ratio (PTR) was used as a measure of the magnitude of seasonal variation. An overall seasonal variation in MD was found [PTR 2.0, 95% confidence interval (95% CI) 1.5-2.6]. There were differences between age groups and between phenotypes, but not between genders. The highest PTRs were observed for the age groups 5-9 y (PTR 4.9, 95% CI 2.1-11.9) and 10-14 y (PTR 3.7, 95% CI 1.4-9.7). No seasonal variation was found for children < 1 y (PTR 1.4, 95% CI 0.6-3.2) or teenagers 15-19 y (PTR 1.6, 95% CI 0.8-3.0). Among phenotypes the highest PTR was observed for C:2a:P1.2,5 (PTR 3.8, 95% CI 1.3-11.2). Thus, seasonal variation depended on age and meningococcal phenotype, the most pronounced seasonality being in 5-14-y-olds and in cases with phenotype C:2a:P1.2,5.

Adolescent↗

PubMed1992

The variation in blood lipid levels described by various measures of overall and abdominal obesity in Danish men and women aged 35-65 years.

The purpose of the study was to describe the proportion of the variation in blood lipid levels [high-density lipoprotein cholesterol (HDLC), low-density lipoprotein cholesterol (LDLC), total cholesterol, very-low-density lipoprotein cholesterol (VLDLC) and triglycerides] explained by different measures of overall obesity [body fat (kg), percentage body fat, or body mass index (kg/m2)] and abdominal obesity [waist/hip ratio, waist/thigh ratio or waist circumference (cm)]. This was done in a Danish population sample of 1523 men and 1464 women aged 35-65 years. This was done to assess, on a population level, the effects on the different lipid levels to be expected from a possible reduction in the level of obesity. The proportion of the variation in lipid levels explained by the various measures of overall obesity differed only slightly, as did the proportion of the variation in lipid levels explained by the various measures of abdominal obesity. In men more of the variation in the blood lipids could be explained by overall obesity than by abdominal obesity, whereas in women the reverse was true. More of the variation in the lipids was explained by overall obesity in men than in women, but more of the variation was explained by abdominal obesity in women than in men. In women the obesity measures predicted between 0% and 11% of the variation in lipid level, and in men the obesity measures predicted between 0% and 14% of the variation. Between 16% and 30% in women and between 5% and 21% in men of the variation in the lipid levels could be explained by obesity, age and several lifestyle variables.(ABSTRACT TRUNCATED AT 250 WORDS)

Abdomen↗

PubMed2005

Sequence variation and the transcriptional activity of the upstream regulatory region in human papillomavirus 16 E7 variants in cervical cancer of Korean women.

In this study, we investigated the sequence variation and different transcriptional activities of the upstream regulatory region (URR) in HPV 16 E7 variants in cervical cancer tissue from Korean women. Using PCR-directed sequencing, the presence of sequence variations in URRs were analyzed and the sites of sequence variation were matched with the known transcriptional factor binding site (TFBS) in 26 HPV 16 E7 variants, 21 cases with A647G (KE7-1, high oncogenic potential) and 5 cases with T732C (KE7-2, low oncogenic potential). In addition, we determined the transcriptional activity of URR in a HPV 16 prototype, and in 4 cases of HPV 16 E7 variants, by using the functional chloramphenicol acetyl transferase (CAT) assay. The 26 HPV 16 E7 variants showed more than 11 sites of sequence variation in the URR. Ten sites of sequence variation were located in the known TFBS and the distribution of sequence variations in the URR showed clear differences between KE7-1 and KE7-2. The sequence variations T7781C and C7786T were matched with YY1 binding sites, G7193T and C7689A were matched with TEF1 binding sites, and C7394T and C7395T were matched with GRE binding sites. The other sequence variations, which were matched with the TFBS, were A7485C, G7489A, T7743G and G7842A. The URR activity of KE7-1 was significantly lower than that of the HPV 16 prototype, whilst KE7-2 was similar. Taken together with the results of the transcriptional activities of KE7-1 and KE7-2, our results suggest that the functional activity and sequence variations of HPV 16 URR may not be related to the oncogenic potential of HPV 16 E7 variants.

Cell Line, Tumor↗

PubMed2006

[Practice pattern and geographic variation in test ordering. A literature review].

OBJECTIVE: To review the available research results in order to identify evidence about geographical variation and practice variation in primary care in the diagnostic test ordering. METHODS: Electronic databases, Medline, Cochrane Library, Science Direct, and Ingenta Select were used to find relevant English language publication between 1989 and 2004. Hand search and the reference lists search for publications were also applied. In addition, researchers were also contacted for publications. Quality of the studies were assessed by using criteria such as sound description of research methodology, detailed and clear presentation of study results. RESULTS: There is a significant (2-4 fold) variation in laboratory test ordering between countries as well as between regions and praxis. There is larger (10-20 fold or more) variation between regions and praxis in the case of diagnostic tests which clinical usefulness is uncertain. The variation between diagnostic test ordering can be larger than variation between medical treatments or invasive interventions. Both geographical and praxis variation could be a result of multiple factors. None of the examined single factor alone was able to explain most of the variations. CONCLUSIONS: Variation in diagnostic test utilisation is significant, and could be caused by multiple factors. Optimisation of diagnostic test ordering and promotion of appropriate utilisation may require multifaceted intervention throughout the health system including changes in regulation, licensing, available capacity, reimbursement/incentive systems and continuous medical education as well as better patient information.

Diagnostic Tests, Routine↗

PubMed1989

Reproducibility of DNA measurements in imprints of thyroid adenoma. Variation sources.

DNA measurement represents a type of quantitative analysis which allows us to gain prognostic information on malignant tumors and to study the natural history of the epithelial neoplasia. However, there are sources of variation in evaluating the DNA content. These include variation due to field selection, variation between observers (interobserver variation), and variation between laboratories (interlaboratory variation). The influence of various variation sources was studied in 4 experiments. When DNA measurements were made from the same microscopic fields, the results did not differ remarkably. However, observer training proved to be important. Intra- and interobserver variation was lower among experienced morphometrists than among inexpert observers. Different laboratories and image analyzers may give different results when the same case is measured. To overcome at least part of the potential variation sources, undergraduates and postgraduates at the Departments of Pathology of Ancona and Kuopio Universities are specially trained in the use and application of morphometry. Special sampling rules should be applied and observers encouraged to follow the rules as uniformly as possible.

Adenoma↗

PubMed1988

Sources of variation introduced into a phagocytosis assay as a result of the isolation of neutrophils from bovine blood.

A study was conducted to examine sources of variation introduced into a phagocytosis assay as a result of the isolation of neutrophils from bovine blood, including variation attributable to isolation of neutrophils from blood, variation between duplicate determinations of percentage phagocytosis, and the variation in the ability of neutrophils isolated from blood (over repeated collections from the jugular vein) to phagocytose. For the phagocytosis assay, jugular venous blood from each of 4 cows was divided into 2 equal portions. The neutrophils were isolated by lysis of red blood cells with 0.2% sodium chloride. The neutrophils (2 x 10(7)) were incubated in duplicate with 32P-labeled Staphylococcus aureus ([32P]SA; 2 x 10(8)) in skimmed milk samples (2.5% final concentration) prepared from 4 cows. This process was repeated thrice on neutrophils isolated from 4 cows at 2-week intervals. The proportions of variation in percentage of 32P-labeled S aureus phagocytosed between duplicate neutrophil isolations and between duplicate assay determinations were 0 and 1%. Differences among skimmed milk sources and among runs, using blood neutrophils taken at different times from the same donor cow, accounted for 62 and 36% of the total variation. The results indicated that variation arising from blood neutrophil isolation introduced into a phagocytosis assay within a single-day trial is of no concern. The large variation among skimmed milk sample sources indicated differences among cows in the ability of their milk to support phagocytosis. The variation in neutrophil isolations over time for any cow was considered too large to allow for evaluation of physiologic and environmental effects on phagocytosis of neutrophils isolated from blood.

Analysis of Variance↗

PubMed1995

Small area variations in health care delivery in Maryland.

OBJECTIVE: Our purpose is a descriptive analysis of variations in hospital use among small areas of Maryland. DATA SOURCE: The data are Maryland patient discharge records from acute care hospitals for 1985-1987 and small area population estimates by age, gender, race, and income. FINDINGS: The common finding was excess geographic variability among Maryland's 115 areas. The hypothesis of uniform rates was rejected for most DRGs, including low-variation mastectomy and hernia repair. Clustering of high-use rates occurred in neighboring areas for orthopedic, vascular, and elective procedures. Admission rates for most nondiscretionary procedures and medical DRGs were reduced in affluent areas while discretionary surgery increased with income level. Elective procedures had extreme variation and were related to income. Coronary artery disease rates declined with income while coronary artery procedure rates increased, indicating that access and patient selection were factors in the use of coronary bypass and angioplasty. CONCLUSIONS: The issue is not the ubiquitous variation among small areas but its extent and identification of geographic patterns. Hospital use is related to demography, morbidity, medical resources, access, selection for care, and physician practice patterns. Heterogeneity of these factors ensures that uniform delivery of health care rarely holds. There is little evidence that incidence of surgical disease is the main source of variation in use of discretionary surgery. Rather, variations reflect differing medical opinion on appropriate use. Without evaluation, excessive use cannot be distinguished from underservice. Morbidity explains the variability of nondiscretionary surgery and conditions related to lifestyle. Access plays an important role for discretionary surgery. Geographic analysis can identify variation and relate incidence to socioeconomic and specific local effects. Hospital data do not permit direct assessment of appropriate care. Understanding the reasons for variation requires information beyond incidence data. The challenge is to identify and explain small area variations or to fix them.

Catchment Area, Health↗

PubMed1996

Physiological variation of serum prostate specific antigen in the 4.0 to 10.0 ng./ml. range in male volunteers.

PURPOSE: Because some patients show a surprising variation in serial serum prostate specific antigen (PSA) values, we determined the intra-individual or physiological variation in serum PSA by collecting sera 2 to 3 week apart without any prostatic manipulation. MATERIALS AND METHODS: Because 4.0 to 10.0 ng./ml. PSA is the critical range for decision making, we asked all men with a PSA in this range to return 2 to 3 weeks later for a second measurement. Total serum PSA was determined by the Hybritech Tandem-R, automated Tosoh AIA-600 and Delfia section immunoassays. Free and complexed serum PSA was determined by the Delfia assays. Between assay variation (first blood specimen retested on a separate day with the second blood specimen) was compared to the physiological variation (first versus second blood specimens). RESULTS: Mean coefficient of variation (95% confidence limits) was 10.5% for between assay and 23.5% for physiological evaluations. The preferred analysis of ratio difference variation provided a factor of 0.138 (between assay) and 0.298 (physiological) for 95% confidence limits. Changes in free or complexed PSA were not the cause of physiological variation. CONCLUSIONS: The intra-individual physiological variation is 2 to 3 times the between assay variation for sera drawn 2 to 3 weeks apart with a PSA of 4 to 10 ng./ml. A serum PSA of 4.0 ng./ml. can increase to 5.2 ng./ml. (4.0 x 0.298) and still be within the physiological variability for 95% confidence limits.

Blood Specimen Collection↗

PubMed1997

Variation of free and total prostate-specific antigen levels: the effect on the percent free/total prostate-specific antigen.

OBJECTIVE: Recent studies have shown that calculations of the percent free/total prostate-specific antigen (PSA) improves the specificity of PSA testing. Characterizing the variability of free PSA and total PSA is necessary to evaluate the utility of an isolated free/total PSA measurement. We investigated the total variation of free and total PSA levels to determine how the percent free/total PSA was affected. DESIGN: Serum was obtained from nine urological patients on 5 different days over a 2-week period. Free and total PSA levels were measured on the day of collection. The total variation expressed in terms of percent coefficient of variation (%CV) was calculated, and the biological variation was derived taking analytical variation into consideration. SETTING: Patients were from Seattle (Wash) Urological Associates, and samples were processed at the Dynacare Laboratory of Pathology, Seattle, Wash. PATIENTS: Nine men (aged 48 to 69 years) were evaluated; three had been diagnosed with prostate cancer, three with benign prostatic hyperplasia, one with chronic prostatitis, one with high-grade prostatic intraepithelial neoplasia, and one was clinically normal. MAIN OUTCOME MEASURES: Total variation for free, total, and percent free/total PSA. RESULTS: The average total variation was 13.9% CV, 7.5% CV, and 10.6% CV for free, total, and percent free/ total PSA, respectively. Biological variation was derived to be 13.0% CV, 5.6% CV, and 8.0% CV for free, total, and percent free/total PSA, respectively. CONCLUSIONS: When applied, these results suggest that there are significant random changes in the numerator and denominator of the free PSA-total PSA ratio that could result in clinical misinterpretation. Clinicians must be aware that free PSA and total PSA levels will fluctuate owing to nonpathologic variation.

Adenocarcinoma↗

PubMed1991

Intraobserver variation in the radiological measurement of the anorectal angle.

Seven experts drew the rectal axes of 18 representative proctographic images on two occasions, with a 1-year interval, in order to assess intraobserver variation in the determination of the anorectal angle (ARA). Intraobserver variation (6%) and interobserver variation (17%) were smallest when the central rectal axis was used to determine the ARA. A strong relation was found between inter- and intraobserver variation (r = 0.77). Intraobserver variation tended to be rather small for pictures made during straining, but a relation with the magnitude of the ARA was not found. Although none of the seven experts could reproduce the rectal axes with less than or equal to 10% variation in all 18 pictures, redrawing of the central rectal axis delivered less than or equal to 10% variation in 86% of determinations. It is concluded that intraobserver variation is influenced by the expertise of the investigator, the method of analysis, and the anorectal configuration to be analyzed. Radiologic assessment of the ARA may yield reliable data on the dynamics of the anorectum if performed by a single investigator on x-ray films that allow confident analysis.

Anal Canal↗

PubMed1994

Rapid enzyme assays investigating the variation in the glycolytic pathway in field-caught populations of Fundulus heteroclitus.

Variation in enzyme expression may be important in evolutionary adaptation, yet is seldom studied. Furthermore, no studies have examined the expression of all enzymes in a defined metabolic pathway. Enzyme concentration is a measure of enzyme expression and was ascertained by assaying maximal activity. Presented here is an analysis of variation of maximal enzyme activity for all the enzymes in a single metabolic pathway, glycolysis, from three clinically distributed populations of the fish, Fundulus heteroclitus. Techniques for rapidly analyzing maximal enzyme activity for all the enzymes of an entire metabolic pathway from many individuals are described. The high degree of repeatability (mean coefficient of variation for replicates, 4.4%) and sensitivity (less than 3 mg of tissue is required to measure all 10 enzymes) of these assays demonstrate the utility of such an approach for analyzing variation among populations for a large numbers of enzymes. Results from these studies indicate that (1) the average coefficient of variation for all enzyme determinations within a population is 45.3% and (2) between populations, the activity of 5 of the 10 glycolytic enzymes are significantly different. This considerable variation occurs even in populations where there is little allelic variation. These data demonstrating substantial variation in enzyme expression support the idea that changes in gene regulation may be as important as, or even more important than, changes in biochemical kinetic parameters in evolutionary processes.

Alleles↗

PubMed2006

Two phases of the contingent negative variation in humans: association with motor and mental functions.

The question of the relationship between contingent negative variation and the mechanisms controlling motor and mental functions has received inadequate study. The aims of the present work were to investigate the relationship between the early and late phases of contingent negative variation and the state of motor and mental functions in patients with Parkinson's disease and to study the effects of levodopa on contingent negative variation. Patients with Parkinson's disease showed significant decreases in the amplitudes and areas of both phases of contingent negative variation as compared with subjects of similar age. Correlation analysis demonstrated a negative relationship between the extent of impairment of coordinatory muscle interactions and the amplitudes of both phases of this variation (p < 0.01). There was a positive relationship between the magnitudes of both phases and the state of mental functions, particularly memory (p < 0.05). Treatment of patients with Parkinson's disease with levodopa was followed by a significant increase in the late phase (p < 0.05). The results obtained here provide evidence for the important role of structures supporting both direct motor control and mental functions in forming both phases of contingent negative variation. The greater effect of levodopa on the late phase of contingent negative variation suggests that the efferent system of the basal ganglia has a greater role in generating the late phase than in organizing the early phase of the variation.

Acoustic Stimulation↗

PubMed1984

Ploidy class-dependent variations during 24 h of glucose-6-phosphate and succinate dehydrogenase activity and single-stranded RNA content in isolated rat hepatocytes.

The time-dependent variations over 24 h of glucose-6-phosphate dehydrogenase (G6PDH) activity, succinate dehydrogenase (SDH) activity and single-stranded RNA (ssRNA) content have been investigated by cytophotometric analysis of cytochemically stained isolated hepatocytes of different ploidy classes from adult male rats. A marked variation of 48% over the day in G6PDH activity of the mononuclear diploid cells was revealed, but no significant variation in the binuclear tetraploid cells. The cells of the inbetween ploidy classes showed an amplitude of variation of 38% (binuclear diploid cells) and 24% (mononuclear tetraploid cells), respectively. All cells showed a maximum activity of the enzyme at the middle of the day and a minimum during the night. The relative enzyme activity per mononuclear diploid cell was significantly higher than the relative activity in the other cells, especially at its maximum. The variation of the SDH activity in hepatocytes isolated from the same rats was similar in all cells, irrespective of their ploidy class. The activity was highest at the end of the activity phase of the animals. The SDH activity per cell was directly proportional to the quantity of genome copies. The ssRNA content of the hepatocytes showed a time-dependent variation with a maximum during the resting phase of the animals and a minimum during their activity phase. The variation was larger in the mononuclear diploid cells than in the cells of other ploidy classes and the ssRNA content was also significantly higher in these cells than in the hepatocytes of other ploidy classes when calculated on the basis of genome copies. It is concluded that the large amplitude of variation over the day and the high relative amount of G6PDH activity and ssRNA content in mononuclear diploid cells is related to the function of these cells as stem cells of the liver parenchyma.

Animals↗

PubMed1994

Quantification of patient to patient variation of skin erythema developing as a response to radiotherapy.

A method is described to determine accurately skin redness during a course of radiotherapy using reflectance spectroscopy utilizing information from across the visible spectrum according to the L*a*b* color coordinate system. The method was used to quantify the development of skin erythema during and after electron beam irradiation of the chest wall following mastectomy. A number of factors were identified which could influence the wide variation in response seen between patients. These were: intra- and inter-observer variation; intra- and inter-patient variation and variation in the actual dose delivered. Statistical analysis, including an analysis of variance of inter- and intra-patient variation, revealed that the major factor that accounts for the observed difference between patients is a true inter-patient variation, with a coefficient of variation, corrected for intra-patient variation, of 43%. Within the narrow dose range administered in this study, there was no demonstrable dose-effect relationship, raising questions about the role of cell death in the basal layer of the epidermis in the pathogenesis of radiation induced erythema.

Adult↗