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PubMed2002

Analysis of solvent central nervous system toxicity and ethanol interactions using a human population physiologically based kinetic and dynamic model.

The effect of acute ethanol-mediated inhibition of m-xylene metabolism on central nervous system (CNS) depression in the human worker population was investigated using physiologically based pharmacokinetic (PBPK) models and probabilistic random (Monte Carlo) sampling. PBPK models of inhaled m-xylene and orally ingested ethanol were developed and combined by a competitive enzyme (CYP2E1) inhibition model. Human interindividual variability was modeled by combining estimated statistical distributions of model parameters with the deterministic PBPK models and multiple random or Monte Carlo simulations. A simple threshold pharmacodynamic model was obtained by simulating m-xylene kinetics in human studies where CNS effects were observed and assigning the peak venous blood m-xylene concentration (C(V,max)) as the dose surrogate of toxicity. Probabilistic estimates of an individual experiencing CNS disturbances given exposure to the current UK occupational exposure standard (100 ppm time-weighted average over 8 h), with and without ethanol ingestion, were obtained. The probability of experiencing CNS effects given this scenario increases markedly and nonlinearly with ethanol dose. As CYP2E1-mediated metabolism of other occupationally relevant organic compounds may be inhibited by ethanol, simulation studies of this type should have an increasingly significant role in the chemical toxicity risk assessment.

Administration, Oral↗
PubMed2005

The role of cardiac troponin I as a prognosticator in critically ill medical patients: a prospective observational cohort study.

INTRODUCTION: Myocardial injury is frequently unrecognized in intensive care unit (ICU) patients. Cardiac troponin I (cTnI), a surrogate of myocardial injury, has been shown to correlate with outcome in selected groups of patients. We wanted to determine if cTnI level measured upon admission is an independent predictor of mortality in a heterogeneous group of critically ill medical patients. METHODS: We conducted a prospective observational cohort study; 128 consecutive patients admitted to a medical ICU at a tertiary university hospital were enrolled. cTnI levels were measured within 6 h of admission and were considered positive (>0.7 ng/ml) or negative. A variety of clinical and laboratory variables were recorded. RESULTS: Both cTnI positive and negative groups were similar in terms of age, sex and pre-admission co-morbidity. In a univariate analysis, positive cTnI was associated with increased mortality (OR 7.0, 95% CI 2.44-20.5, p < 0.001), higher Acute Physiology and Chronic Health Evaluation (APACHE) II scores and a higher rate of multi-organ failure and sepsis. This association between cTnI and mortality was more pronounced among elderly patients (>65 years of age). Multivariate analysis controlling for APACHE II score revealed that elevated cTnI levels are not independently associated with 28-day mortality. CONCLUSION: In critically ill medical patients, elevated cTnI level measured upon admission is associated with increased mortality rate. cTnI does not independently contribute to the prediction of 28-day mortality beyond that provided by APACHE II.

APACHE↗
PubMed2004

Association of carotid intima-media thickness with mesenteric, preperitoneal and subcutaneous fat thickness.

Carotid intima-media thickness (IMT) is an established surrogate marker for atherosclerosis. We have previously reported that abdominal fat, notably mesenteric fat, was a major explanatory variable for multiple cardiovascular risk factors. Given the intimate relationships between visceral fat, cardiovascular risk factors and atherosclerosis, we hypothesize that there are independent relationships between mesenteric fat and carotid IMT. Two hundred and eighty-two Chinese subjects (M: 129, F: 153; mean body mass index (BMI): 23.8 kg/m(2); age range: 20-68 years) were recruited. Maximum carotid IMT as well as maximum mesenteric, preperitoneal and subcutaneous fat thickness were measured by carotid and abdominal ultrasound examinations, respectively. Obesity index and conventional cardiovascular risk factors were assessed by physical examination and blood taking. On univariate analysis, mesenteric but not preperitoneal fat thickness was the major correlate with carotid IMT in both men and women. There was also a weak correlation between carotid IMT and subcutaneous fat thickness in women. On multivariate analysis, mesenteric fat thickness was an independent determinant of carotid IMT after adjustment for subcutaneous and preperitoneal fat thickness, age, gender, blood pressure, insulin resistance, lipid and glycaemic parameters. The association of mesenteric fat thickness with carotid IMT appeared stronger in women than in men, which however was not confirmed on multivariate analysis. In conclusion, mesenteric fat thickness measured on ultrasound showed significant association with carotid IMT, lending further support to the linking role of portal adipose tissue in obesity-related atherosclerosis. Effect of gender on the relationships of mesenteric fat with atherosclerosis risk require further elucidation. Measurement of mesenteric fat thickness may be a useful indicator of regional fat distribution in the assessment of cardiovascular risks.

Adipose Tissue↗
PubMed1999

Hospital volume can serve as a surrogate for surgeon volume for achieving excellent outcomes in colorectal resection.

OBJECTIVE: To examine the association of surgeon and hospital case volumes with the short-term outcomes of in-hospital death, total hospital charges, and length of stay for resection of colorectal carcinoma. METHODS: The study design was a cross-sectional analysis of all adult patients who underwent resection for colorectal cancer using Maryland state discharge data from 1992 to 1996. Cases were divided into three groups based on annual surgeon case volume--low (< or =5), medium (5 to 10), and high (>10)--and hospital volume--low (<40), medium (40 to 70), and high (> or =70). Poisson and multiple linear regression analyses were used to identify differences in outcomes among volume groups while adjusting for variations in type of resections performed, cancer stage, patient comorbidities, urgency of admission, and patient demographic variables. RESULTS: During the 5-year period, 9739 resections were performed by 812 surgeons at 50 hospitals. The majority of surgeons (81%) and hospitals (58%) were in the low-volume group. The low-volume surgeons operated on 3461 of the 9739 total patients (36%) at an average rate of 1.8 cases per year. Higher surgeon volume was associated with significant improvement in all three outcomes (in-hospital death, length of stay, and cost). Medium-volume surgeons achieved results equivalent to high-volume surgeons when they operated in high- or medium-volume hospitals. CONCLUSIONS: A skewed distribution of case volumes by surgeon was found in this study of patients who underwent resection for large bowel cancer in Maryland. The majority of these surgeons performed very few operations for colorectal cancer per year, whereas a minority performed >10 cases per year. Medium-volume surgeons achieved excellent outcomes similar to high-volume surgeons when operating in medium-volume or high-volume hospitals, but not in low-volume hospitals. The results of low-volume surgeons improved with increasing hospital volume but never equaled those of the high-volume surgeons.

Aged↗
PubMed2003

Efficacy of cyclophosphamide combined with prednisolone in patients with AA amyloidosis secondary to rheumatoid arthritis.

Secondary amyloid A (AA) amyloidosis is an uncommon yet important complication of rheumatoid arthritis (RA). It is one of the most relentless of the extra-articular features of RA, and suitable treatments have not yet been found. We studied the efficacy of cyclophosphamide (CYC) combined with prednisolone (PSL) in amyloidotic patients who had serum amyloid A (SAA) 1.3 genotype, which is a risk factor for secondary amyloidosis in Japanese RA patients. Fifteen RA patients who were SAA1.3 homo- and heterozygotes with biopsy-confirmed AA amyloidosis were treated with a combination of CYC and PSL. Laboratory variables of C-reactive protein (CRP), rheumatoid factor (RF), erythrocyte sedimentation rate (ESR), serum albumin (Alb), serum creatinine (Cre) and Lansbury's index were carried out by statistical analysis of changes between before and during the medication. According to the Mann-Whitney rank test, CRP, RF, ESR, Alb and Cre levels improved significantly with the combination treatment (p<0.05). Also, paired t-tests showed significance in Lansbury's index between before and during the medication (p=0.007). CYC combined with PSL ameliorated not only laboratory markers but also clinical rheumatoid activity in patients with amyloidosis secondary to RA, whose genotypes were SAA1.3 homo- and heterozygous. CRP, ESR, RF, Alb and Cre will be surrogate markers of therapeutic efficacy. The combination of CYC and PSL appears to be beneficial for Japanese RA patients who are SAA1.3 homo- and heterozygous carriers, associated with secondary AA amyloidosis.

Aged↗
PubMed2003

Predictive value of urinary retinol binding protein for graft dysfunction after kidney transplantation.

UNLABELLED: High concentrations of retinol binding protein (RBP) are found in the urine of patients with tubulointerstitial injury. We evaluated the predictive value of urinary RBP (RBPu) for development graft dysfunction after kidney transplantation. METHODS: Serum creatinine and RBPu were prospectively measured at months 3, 6, and 12 in 221 kidney transplant patients. Baseline graft function was defined as the lowest serum creatinine value during the first 3 months after transplantation. Graft dysfunction was assessed at 1 year as a >-20% or >-30% change in the inverse creatinine ((Delta)1/Cr) compared to baseline value at month 3. RESULTS: Among 183 patients with normal graft function (Cr </= 1.6 mg/dL) the mean (Delta)1/Cr from month 3 to 12 was -17 +/- 22% (-80% to + 44%). Using a receiver operating characteristic (ROC) analysis, concentrations higher than 0.6 mg/L showed the best predictive value for diagnosis of graft dysfunction at 1 year. Mean (Delta)1/Cr from month 3 to 12 was -13 +/- 20% for those with RBP < 0.6 mg/L vs -20 +/- 23% in those with RBPu > 0.6 mg/L (95% CI = -13% to -1.3%, P =.018). The percentage of patients with >-20% or >-30% (Delta)1/Cr was higher among patients with RBPu > 0.6 mg/L (34% vs 47%, P =.042; 21% vs 34%, P =.035). RBPu > 0.6 mg/L was the only variable independently associated with >-30% (Delta)1/Cr at 1 year, with an odds ratio (OR) of 1.95 (95% CI 0.99 to 3.80, P =.05). CONCLUSIONS: RBPu may serve as a surrogate marker for graft dysfunction early after transplantation for patients with normal graft function, allowing early institution of intervention therapies to prolong allograft survival.

Adolescent↗
PubMed2002

Using attitudinal indicators to explain the public's intention to have recourse to gamete donation and surrogacy.

BACKGROUND: Although the donation and receipt of gametes has become an integral part of infertility management, previous research in the field of social attitudes and intention to use medical technologies is limited. This study aimed to investigate attitudinal indicators and their potential relationship with the public's intention to have recourse to gamete donation and surrogacy. METHODS: A total of 365 individuals of reproductive age (49.3% men and 50.7% women) completed a questionnaire referring to their intention to receive or donate sperm/oocytes and their acceptance of becoming a commissioning couple or surrogate mother, and also to explore their attitudes towards gamete donation and surrogacy. Two attitudinal indicators emerged from the principal component analysis identifying (i). recipients' and donors' choice for anonymity, donors' renunciation of parental obligations and refusal of children's rights to know their biological parents and (ii). favourable attitudes towards legislative and financial measures to be adopted by the Government for the promotion of reproductive technologies. RESULTS: It was found that the indicator of 'Donors Anonymity and Refusal of Children's Rights' (DARCR) and the 'Legislative and Financial Support' (LFS) scale are positively associated with intention to have recourse to Gamete Donation and Surrogacy (GDS) (regression coefficients 0.31 and 1.08 respectively). Moreover, among the other variables used in the analysis only the 'church attendance' variable is negatively related with reported rates of intention to have recourse to GDS (P = 0.029), suggesting that the more religious respondents are less willing to use GDS. CONCLUSION: Social, legislative and financial implications provide a convenient rationale for adopting a favourable intention towards reproductive technologies. The findings of the present research should be given close consideration by policy makers and health education campaigns.

Adult↗
PubMed1999

Reasoning about data with directed graphs.

This paper constructs graphical models for two important analysis problems to demonstrate how graphs can clearly represent complex relationships. A powerful property of graphical models called d-separation describes the statistical associations in a given graphical model. This allows the effects of unmeasured variables to be predicted, and suggests conditional analyses which can distinguish conjectured models. If an assumption called quasi-linearity is made, further conclusions can be drawn based on the structure of the graph and d-separation. Making the quasi-linearity assumption explicit also contributes to our understanding of which aspects of our causal intuition are based on linearity assumptions. The examples that we consider are the scientific interpretation of interventions and the evaluation of the validity of candidate surrogate endpoints for clinical trials. Intervention studies can be plagued by non-compliance with assigned treatment and ambiguity in interpreting results when treatment assignment manipulates multiple factors. We show graphically the conclusions that can be drawn under various assumptions. The topic of surrogate endpoints is addressed in causal terms and modelled graphically.

Bayes Theorem↗
PubMed2002

Parent visual analogue scale ratings of children's pain do not reliably reflect pain reported by child.

OBJECTIVES: To determine whether parent and child visual analogue scale (VAS) scores for the pain associated with acute conditions in the child agree sufficiently for these methods of measurement to be considered interchangeable in pain and analgesia research. DESIGN: This was a prospective, two-group, repeated measures, blinded study in an urban pediatric emergency department. Children aged 8 to 15 years seeking treatment for painful conditions and the parents of these children were asked to rate the child's pain independently using a VAS on as many as four occasions at 20-minute intervals. Both participants were blinded to their previous rating and the rating of the other participant. The main outcome measure was the correlation of child and parent VAS pain scores by Pearson correlation and bias plot (Bland-Altman) analysis of agreement between tests. RESULTS: Seventy-eight child-parent sets participated, yielding 289 VAS pain score comparison pairs for evaluation. The correlation between child and parent VAS pain scores was 0.63 (95% CI, 0.56-0.70). Bias plot analysis revealed a bias of 5% and 95% limits of agreement from -38 to +47 mm. The degree of difference between child and parent scores was variable, but there was an increasing tendency for parents to underestimate the child's pain when the child recorded VAS pain scores at the higher end of the scale. CONCLUSIONS: Parents' VAS score ratings of their children's pain correlate only moderately with the children's VAS pain scores and show poor levels of agreement. The difference between the measures is variable and appears to be more marked when the child reports a higher VAS score. This research raises doubt about whether parental rating of a child's pain is an appropriate surrogate marker in pediatric pain and analgesia research.

Acute Disease↗
PubMed2005

Hippocampal damage in newly diagnosed focal epilepsy: a prospective MRI study.

OBJECTIVE: To examine the longitudinal appearance of hippocampal (HC) damage in a prospective follow-up study of patients with newly diagnosed epilepsy. METHODS: A total of 103 patients with newly diagnosed focal epilepsy were scanned with MRI before antiepileptic medication was started. Serial MRI studies were scheduled after 1, 2 to 3, and 5 years of treatment in the ongoing follow-up study. Volumes of the HC were measured from MRI scans according to the Cavalieri method of modern design stereology and compared at different time points together with clinical variables. RESULTS: No difference was observed in the mean HC volumes between controls and patients at baseline, after 1, 2 to 3, and 5 years of follow-up. Individual analysis showed that 8% of patients had HC damage at the time of the diagnosis and 13% of patients developed HC volume decrease during 2 to 3 years of follow-up. These patients had longer duration of seizure disorder and larger seizure number before the epilepsy was diagnosed and treatment started compared with patients who did not show HC damage. CONCLUSIONS: Hippocampal volume decreases occur in individual patients with newly diagnosed focal epilepsy during the first years of treatment. The data obtained suggest that hippocampal volumetry provides a surrogate marker of the epileptic process.

Adolescent↗
PubMed2005

A longitudinal measurement error model with a semicontinuous covariate.

Covariate measurement error in regression is typically assumed to act in an additive or multiplicative manner on the true covariate value. However, such an assumption does not hold for the measurement error of sleep-disordered breathing (SDB) in the Wisconsin Sleep Cohort Study (WSCS). The true covariate is the severity of SDB, and the observed surrogate is the number of breathing pauses per unit time of sleep, which has a nonnegative semicontinuous distribution with a point mass at zero. We propose a latent variable measurement error model for the error structure in this situation and implement it in a linear mixed model. The estimation procedure is similar to regression calibration but involves a distributional assumption for the latent variable. Modeling and model-fitting strategies are explored and illustrated through an example from the WSCS.

Blood Pressure↗
PubMed1996

Influence of location and staff knowledge on quality of retail pharmacy prescribing for childhood diarrhea in Kenya.

BACKGROUND: Retail pharmacies are important sources of advice on pharmaceuticals in developing countries, where many purchasing decisions are unmediated by medical professionals. For childhood diarrhea, choice of drug sales in pharmacies has been found to be consistently poor, whether with or without prescription, as evidenced by a low use of effective oral rehydration salts (ORS) and high use of marginally effective or ineffective products such as antimotility agents, adsorbents, and antimicrobials. Little information is available about factors influencing prescribing by pharmacy personnel in these settings. This paper reports results of an analysis which examined the influence of rural versus urban location, neighborhood socio-economic status (SES), and clinical knowledge of pharmacy assistants on quality of prescribing in retail pharmacies in Kenya. METHODS: Using WHO treatment guidelines, we measured quality of prescribing in childhood diarrhea as: (1) the proportion of client encounters in which ORS is prescribed (indicating higher quality practice); and (2) the proportion of visits in which an antidiarrheal product is prescribed (lower quality practice). We obtained data on prescribing in a simple case of childhood diarrhea using surrogate patient visits to 91 pharmacies located in the major urban area of Kenya (Nairobi) and four rural towns. Multivariate logistic regression was used to examine the association between pharmacy predictor variables and the quality of prescribing. RESULTS: No consistent relationship was found between the clinical knowledge of pharmacy assistants and quality of prescribing. Controlling for number of products prescribed, gender of the assessor, and level of knowledge, multivariate analyses indicated that in comparison to rural pharmacies, the odds of prescribing ORS were significantly higher in pharmacies located in high SES (OR = 4.7; 95% CI = 1.4,16.1) or middle SES (OR = 4.5; CI = 1.9,10.6) urban neighborhoods; the odds in low SES urban pharmacies were similar to those in rural areas (OR = 2.0; CI = 0.6,6.2). The odds of prescribing antidiarrheal products did not differ significantly in any geographic area. CONCLUSIONS: Location of a retail pharmacy in a rural area or in a low-income urban neighborhood was associated with suboptimal quality of prescribing as evidenced by lower use of ORS. No relationship between clinical knowledge and quality of practice was detected. Future research is needed to examine such factors as the influence of intra-pharmacy authority structure, perceived efficacy of pharmaceuticals, local patterns of physician practice, and economic incentives on the quality of prescribing.

Adult↗
PubMed2006

Interictal EEG as a physiological adaptation. Part II. Topographic variability of composition of brain oscillations in interictal EEG.

OBJECTIVE: In the present experimental study, we examined topographic variability of composition of brain oscillations and their temporal behavior in frequencies from 0.5 to 30 Hz of interictal EEG without epileptiform abnormalities and healthy EEG. METHODS: Spatio-temporal variability of brain oscillations (indexed by short-term EEG spectral patterns (SPs)) was assessed by the probability-classification analysis of SPs. As a result, multi-dimensional SP-vector for each analysis EEG epoch was obtained. RESULTS: It was demonstrated that interictal EEG was characterized (a) by a significant decrease of spatio-temporal variability of brain oscillations, (b) by longer periods of temporal stabilization for operational modules which comprise larger number of cortical areas, and (c) by significantly more intermittent recurrence when compared with EEG of control subjects. Generally it was shown that EEG channels display different states of coordination independently on their correlation and coherence using brain oscillations at multiple frequencies. CONCLUSIONS: Results of this study suggested that EEG correlate of chronic epileptogenesis in the brain is a particular metastable state of biopotential field, which can be estimated by SP-vector. The fact that all results were significantly different from surrogate EEGs reflects a nonoccasional and thus, most likely, an adaptive nature of spatio-temporal reorganization in interictal EEG. SIGNIFICANCE: Parameters of spatio-temporal organization of interictal EEG without the signs of epileptiform activity can be considered as additional information in premorbid diagnostics of status epilepticus, and may also provide insights into basic laws that govern brain oscillations in general.

Action Potentials↗
PubMed1998

Evaluation and validation of a Crohn's disease inflammatory activity index reflecting pattern of endoscopic severity.

BACKGROUND: This study was designed to investigate objective variables assessing the inflammatory activity of Crohn's disease accessible for routine management and their suitability to act as surrogate indicators for endoscopic alterations. METHODS: Thirty-six patients were included in a prospective study and underwent endoscopic investigation, 18 with clinically exacerbated disease and 18 after acute-phase conservative therapy. The endoscopic findings were classified to define the dependent variable, yielding two categoric levels: acute active disease and remission. The extent of affected mucosal area was not taken into consideration. The serum variables alpha1-antitrypsin, acid alpha1-glycoprotein (AGP), C-reactive protein (CRP), sialic acids, prealbumin (PAB), and albumin were used as independent variables to predict the dependent variable. To compare the results with common indices, the Crohn's Disease Activity Index (CDAI) and van Hees Index were calculated. RESULTS: The following model was calculated by stepwise logistic regression analysis: if AGP (mg/dl) -4.2 x PAB (mg/dl) > or =0.8, then endoscopically active disease will be predicted with a sensitivity of 100% and a specificity of 95% (P < 0.001). The predictive values of the single variables, CDAI, and van Hees Index were lower. For validation of results an analogous study was performed including 44 patients, 29 with active disease and 15 controls. The existence of the model was confirmed, again showing high values for sensitivity (86%) and specificity (100%). CONCLUSIONS: On a qualitative level focusing on clinical relevance, the endoscopic and biologic findings of Crohn's disease are highly associated. In addition to clinical assessment, usage of the developed index as a rationale contributing to therapeutic decisions in the short- and long-term management might be reasonable.

Biomarkers↗
PubMed2005

Correlation between PCDD/F, PCB and PCBz in coal/waste combustion. Influence of various inhibitors.

In the flue gas of co-combustion of solid waste and coal in a laboratory scale furnace high concentrations of polychlorinated dibenzo-p-dioxin and furans (PCDD/F), polychlorinated biphenyls (PCB) and polychlorinated benzenes (PCBz) have been detected. These toxic emissions have been reduced by the help of various inhibitors added to fuel before incineration. Knowledge of the congener pattern and homologue profiles of PCDD/F, PCB and PCBz is important to elaborate the mechanism of formation and inhibition of the toxic compounds formed during co-combustion of solid waste and coal. Principle component analysis (PCA) is used in order to find the similarity between the samples and separate them according their toxicity. By the help of the component analysis (CA) the best correlated congeners are effectively detected. Using linear regression between the independent variables and the indicator parameters various good correlated pairs between PCDD/F, PCB and PCBz have been elaborated. Generally it was found that the samples with higher toxicity show a good correlation between tetra- and pentachlorinated benzenes and tetra- and pentachlorinated dibenzo-p-furans. The best indicator parameter for PCDD/F World Health Organization toxic equivalent (WHO-TEQ) among the PCBz congeners investigated is 1,2,4,5-TCBz. This isomer is also significantly correlated with PCDD/F WHO-TEQ and with the sum of PCDD/F WHO-TEQ and PCB WHO-TEQ. However for samples with higher percentage of inhibitors the above mentioned relationship between the surrogate and WHO-TEQ disappeared. The PCB homologues and congeners show no correlation with PCBz and PCDD/F homologues and congeners.

Air Pollutants↗
PubMed2002

Outcomes research in mental health. Systematic review.

BACKGROUND: Outcomes research involves the secondary analysis of data collected routinely by clinical services, in order to judge the effectiveness of interventions and policy initiatives. It permits the study of large databases of patients who are representative of 'real world' practice. However, there are potential problems with this observational design. AIMS: To establish the strengths and limitations of outcomes research when applied in mental health. METHOD: A systematic review was made of the application of outcomes research in mental health services research. RESULTS: Nine examples of outcomes research in mental health services were found. Those that used insurance claims data have information on large numbers of patients but use surrogate outcomes that are of questionable value to clinicians and patients. Problems arise when attempting to adjust for important confounding variables using routinely collected claims data, making results difficult to interpret. CONCLUSIONS: Outcomes research is unlikely to be a quick or cheap means of establishing evidence for the effectiveness of mental health practice and policy.

Confounding Factors, Epidemiologic↗
PubMed2006

Accuracy of developing tooth length as an estimate of age in human skeletal remains: the deciduous dentition.

Dental age assessments are widely used to estimate age of immature skeletal remains. Most methods have relied on fractional stages of tooth emergence and formation, particularly of the permanent dentition, for predicting the age of infants and very young children. In this study, the accuracy of regression equations of developing deciduous tooth length for age estimation (Liversidge et al.) is tested on a sample of 30 Portuguese subadult skeletons of known age at death. Overall the method shows high accuracy and the average difference between estimated and chronological age is between 0.20 and -0.14 years when using single teeth, and 0.06 years, when using all available teeth. However, there is a tendency for the deciduous molars to provide overestimates of chronological age. Results show that age estimates can be obtained within +/-0.10 years with a 95% confidence interval when several teeth are used. Overall between-tooth agreement in age estimates decreases with increasing age but there is less variability of estimates with more teeth contributing to overall mean age. One seemingly limitation of this method may be the fact that it was developed by combining the maxillary and mandibular teeth. The other is related to the accuracy with which radiographic tooth length can be used as a valid surrogate for actual tooth length. Nevertheless, the advantages of this metric method surpass the limitations of chronologies based on stages of dental development.

Age Determination by Teeth↗
PubMed2000

Indirect estimates of body composition are useful for groups but unreliable in individuals.

OBJECTIVE: To assess the usefulness of the body mass index (BMI) in identifying individuals classified as overweight or obese based on estimates of body fat percentage (BF%) obtained by the deuterium dilution (BF%DD) method. In addition, to assess the accuracy of bioelectrical impedance analysis (BIA) and skinfold thickness (SFT) measurements in the estimation of body composition of Australians at the individual and group level. DESIGN: Cross-sectional study. SUBJECTS: One hundred and seventeen healthy Australian volunteers of European descent, comprising of 51 males and 66 females, ranging in age from 19 to 77 y. MEASUREMENTS: BMI was calculated from body weight and height. Fat-free mass (FFM) was estimated from measures of total body water (TBW) using deuterium dilution (FFM(DD)), SFT using the equations of Durnin and Womersley (Br J Nutr 1974; 32: 77-97) (FFM(SFT)), and BIA using the equations of Lukaski et al (J Appl Physiol 1986; 60: 1327-1332) (FFM(Lu)), Segal et al (Am J Clin Nutr 1988; 47: 7-14) (FFM(Se)) and Heitmann (Eur J Clin Nutr 1990; 44: 831-837) (FFM(He)). Estimates of fat mass (FM) were calculated as the difference between body weight and FFM, while BF% was calculated by expressing FM as a percentage of body weight. RESULTS: BMI had poor sensitivity and positive predictive value in identifying individuals as being overweight/obese as classified by BF%DD. Furthermore, estimates of FFM (and hence FM) from BIA or SFT could not be used interchangeably with DD, without the risk of considerable error at the individual level. At the group level errors were relatively smaller, though statistically significant. While FFM(SFT) could be corrected by the addition of the bias (1.2 kg in males and 0.8 kg in females), no simple correction was possible with BIA estimates of FFM for any of the equations used. However, an accurate prediction of FFM(DD) was possible from the combination of FFM(He), biceps SFT and mid-arm circumference in both males and females. The bias of this prediction was small (<0.15 kg), statistically non-significant in both sexes, and unrelated to the mean FFM obtained by the two methods. The revision of Heitmann's estimate of FFM using anthropometric variables described in this study had the best sensitivity (79%), specificity (96%) and positive predictive value (92%) in identifying overweight/obese individuals in comparison to the other equations tested. CONCLUSION: BMI was a poor surrogate for body fatness in both males and females. The currently recommended equations for the prediction of body composition from SFT and BIA provided inaccurate estimates of FFM both at the individual and group level as compared to estimates from DD. However, Heitmann's equations, when combined with measures of the biceps SFT and mid-arm circumference, provided better estimates of FFM both at the individual and group level.

Adipose Tissue↗