Is bioelectrical impedance accurate for use in large epidemiological studies?

Percentage of body fat is strongly associated with the risk of several chronic diseases but its accurate measurement is difficult. Bioelectrical impedance analysis (BIA) is a relatively simple, quick and non-invasive technique, to measure body composition. It measures body fat accurately in controlled clinical conditions but its performance in the field is inconsistent. In large epidemiologic studies simpler surrogate techniques such as body mass index (BMI), waist circumference, and waist-hip ratio are frequently used instead of BIA to measure body fatness. We reviewed the rationale, theory, and technique of recently developed systems such as foot (or hand)-to-foot BIA measurement, and the elements that could influence its results in large epidemiologic studies. BIA results are influenced by factors such as the environment, ethnicity, phase of menstrual cycle, and underlying medical conditions. We concluded that BIA measurements validated for specific ethnic groups, populations and conditions can accurately measure body fat in those populations, but not others and suggest that for large epdiemiological studies with diverse populations BIA may not be the appropriate choice for body composition measurement unless specific calibration equations are developed for different groups participating in the study

OSTEOCALCIN AND BONE-SPECIFIC ALKALINE PHOSPHATASE IN SICKLE CELL HAEMOGLOBINOPATHIES

Osteocalcin or bone gamma-carboxyglutamic acid (gla) protein and Bone-specific alkaline phosphatase (b-AP) total protein levels were evaluated as indicators of bone turnover in twenty patients with sickle cell haemoglobinopathies and in twenty normal healthy individuals. The serum bone-specific alkaline phosphatase total protein level was measured by immunoradiometric (IRMA) method. The concentrations of serum bone-specific alkaline phosphatase total protein were higher in the study group than in the control group (p < 0.05). The serum osteocalcin (BGP) showed no significant difference with the control healthy subjects. There was no correlation between the serum osteocalcin and serum bone-specific alkaline phosphatase total protein in the patient group. In conclusion, serum bone-specific alkaline phosphatase total protein determined or measured by IRMA can be considered a sensitive marker of bone turnover and could be especially useful as valuable non-invasive biochemical marker for identifying sickle cell patients with bone complications

Body proportions in three Nigerian tribes

Prediction equations of body composition based on measurements of whole-body bioelectrical impedance analysis (BIA) have been found to be population-specific. It was hypothesised that this may be, in part, due to differences in proportional limb lengths between ethnic or racial groups. As a preliminary to a survey of body composition in urban Nigerians using BIA, the relative limb lengths of the three major tribal groups (Hausa, Yoruba and Ibo) were determined. We found small (5-9%) but significantly longer limb lengths in Nigerians compared to a Caucasian population, but no significant differences between tribes. This implies that BIA prediction equations generated in a Caucasian population are inappropriate for use in a Nigerian population

Salt-sensitivity in normotensive and hypertensive Nigerians

Background: Salt-sensitivity increases the risk for the development of high blood pressure in susceptible persons and also increases the risk for cardiovascular events and mortality. Objective: The study is to determine the pattern of saltsensitivity among normotensive and hypertensive Nigerians. Methods: Twenty-eight (28) hypertensive subjects (HT) and twenty-five (25) age-matched normotensive controls (NT) were given 200mmol/day salt as sodium chloride for 5 days after control parameters had been determined. Subjects were regarded as salt-sensitive when change in mean arterial blood pressure (cMABP) between baseline levels and that after salt loading was \u3e5mmHg. Results: Systolic blood pressure and mean arterial blood pressure but not diastolic blood pressure rose significantly (p \u3c 0.05 and p \u3c0.001 respectively) in NT subjects while all the parameters showed significant increases in hypertensive subjects (SBP p\u3c0.01; DBP p \u3c 0.001; MABP p \u3c 0.0001). More hypertensive subjects (60.7%) were saltsensitive compared with normotensive (52.0%) subjects (p\u3c0.05). Conclusion: This study has demonstrated pressor responses to acute salt-loading in normotensive and hypertensive Nigerians and salt-sensitivity was higher in hypertensive subjects

Association between ethnicity, body mass index and bioelectrical impedance: implications for the population-specificity of prediction equations

No Abstrac