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PubMed2006

On the misinterpretation of the correlation coefficient in pharmaceutical sciences.

The correlation coefficient is often used and more often misused as a universal parameter expressing the quality in linear regression analysis. The popularity of this dimensionless quantity is evident as it is easy to communicate and considered to be unproblematic to comprehend. However, illustrative examples will demonstrate that the correlation coefficient is highly ineffective as a stand-alone quantity without reference to the number of observations, the pattern of the data and the slope of the regression line. Much more efficient quality methodologies are available where the correct technique depends on the purpose of the investigation. These relevant and precise methods in quality assurance of linear regression as alternative to the correlation coefficient are presented.

Data Interpretation, Statistical↗

PubMed1990

Dose-related effects of succinylcholine on the adductor pollicis and masseter muscles in children.

This study was performed to determine the effects of various doses of succinylcholine on resting tension and evoked twitch height at the masseter and adductor pollicis muscles in children. Twenty patients, aged 3-10 yr, ASA physical status I or II, were randomly assigned to receive succinylcholine 0.15, 0.25, 0.50 or 1.00 mg.kg-1, during halothane-nitrous oxide anaesthesia. Supramaximal train-of-four stimulation was applied simultaneously to the ulnar nerve and the nerve to the masseter. Transducers recorded force at the jaw and the thumb. Maximum blockade of the first twitch (T1) and maximum resting tension change were measured. Potency of succinylcholine at the two muscles was estimated by linear regression of the logit transformation of T1 versus log dose. The relationship between resting tension change and log dose was established by linear regression. The masseter muscle was more sensitive to succinylcholine than the adductor pollicis with an ED95 of 0.28 +/- 0.02 (mean +/- SEM) vs 0.44 +/- 0.05 mg.kg-1 (P less than 0.05). Onset of neuromuscular blockade was faster at the masseter, and recovery occurred simultaneously in both muscles. A dose-related increase in resting tension was observed in both muscles, but its magnitude was five times greater at the masseter. With succinylcholine, 1 mg.kg-1, this increase was 51.6 +/- 16.8 g at the masseter and 9.1 +/- 2.3 g at the adductor pollicis. Tension returned to baseline within 1-2 min.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia, Inhalation↗

PubMed1990

Toxication of MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) and analogs by monoamine oxidase. A structure-reactivity relationship study.

MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) elicits motor deficits similar to those observed in Parkinson's disease. Before exerting its neurotoxic action, MPTP must be activated by brain monoamine oxidase (MAO) to the neurotoxic metabolite MPP+ (1-methyl-4-phenylpyridinium). MPTP derivatives differ in their reactivity as MAO substrates and in their neurotoxicity. A structure-reactivity relationship study based on literature data was undertaken in order to determine the key features in the structure of MPTP and analogs that are responsible for the reactivity towards MAO. Thirty-three MPTP derivatives (including MPTP itself) were included in the study. To explain the reactivity towards MAO of the 33 MPTP analogs, different statistical methods (principal component analysis, multiple linear regression analysis) as well as the CoMFA (Comparative Molecular Field Analysis) approach, a new tool in structure-activity correlations, were used. Linear regression analysis failed to yield any predictive model, but suggested some trends. In contrast, the CoMFA approach was successful in correlating structural features and MAO reactivity. Coefficient contour maps showed where differences in the steric field (van der Waals' interactions) are most highly associated with differences in MAO reactivity. Several positive (in the ortho- and meta-position of the phenyl group) and negative (in the para-position of the phenyl group; beyond the N-methyl group) interaction regions were identified. Some structural features of the MAO active site could be postulated. First, the N-methyl group has the ideal size and elicits ideal interactions within the MAO active pocket, while smaller or larger groups are less favorable; second, para-substituent on the phenyl ring produce steric hindrances and are unfavorable to reactivity; third, ortho- and meta-substituents may have stabilizing interactions within the active pocket and are favorable to the reactivity. Moreover the model derived by CoMFA allowed us to make successful predictions of reactivity towards MAO for several additional tetrahydropyridines.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗

PubMed1995

Expression of proliferation-associated antigens in cervical carcinoma: correlations among indexes.

Monoclonal antibodies recognizing proliferation-associated antigens can be employed in formalin-fixed, paraffin-embedded sections. The MIB1, PC10, 19A2, cytoplasmic p105 indexes, and mitotic index in hematoxylin and eosin stained preparations represent the growth, S-phase and mitotic fractions, respectively. The specimens consecutively taken from 194 patients with stage III cervical carcinoma were investigated immunohistochemically. Cancer cells that were positive for MIB1, PC10 and 19A2 showed a nuclear staining pattern. Mitotic cancer cells were strongly positive for p105 in their cytoplasm and also showed chromosomal p105 positivity. The mean indexes for MIB1, PC10, 19A2 and cytoplasmic p105 and the mitotic index in hematoxylin and eosin preparations were 43% (range, 18-74%), 26% (5-60%), 15% (0-60%), 2% (0-11%) and 0.6% (0-6.3%), respectively. The linear regression analysis showed only a very weak or no correlations between the MIB1, PC10, 19A2 and cytoplasmic p105 indexes among the patients (linear regression correlation coefficient r = 0.10 to 0.32). We conclude that (1) the MIB1 growth fraction, PC10 or 19A2 S-phase fraction, and the mitotic fraction show wide variations among patients with cervical carcinoma and (2) the PC10 or 19A2-positive S-phase fraction and the mitotic fraction of cervical carcinoma should not be used instead of the MIB1 growth fraction as equivalent to cycling cancer cell population.

Adult↗

PubMed1998

Magnetic resonance thermometry during hyperthermia for human high-grade sarcoma.

PURPOSE: To determine the feasibility of measuring temperature noninvasively with magnetic resonance imaging during hyperthermia treatment of human tumors. METHODS: The proton chemical shift detected using phase-difference magnetic resonance imaging (MRI) was used to measure temperature in phantoms and human tumors during treatment with hyperthermia. Four adult patients having high-grade primary sarcoma tumors of the lower leg received 5 hyperthermia treatments in the MR scanner using an MRI-compatible radiofrequency heating applicator. Prior to each treatment, an average of 3 fiberoptic temperature probes were invasively placed into the tumor (or phantom). Hyperthermia was applied concurrent with MR thermometry. Following completion of the treatment, regions of interest (ROI) were defined on MR phase images at each temperature probe location, in bone marrow, and in gel standards placed outside the heated region. The median phase difference (compared to pretreatment baseline images) was calculated for each ROI. This phase difference was corrected for phase drift observed in standards and bone marrow. The observed phase difference, with and without corrections, was correlated with the fiberoptic temperature measurements. RESULTS: The phase difference observed with MRI was found to correlate with temperature. Phantom measurements demonstrated a linear regression coefficient of 4.70 degrees phase difference per degree Celsius, with an R2 = 0.998. After human images with artifact were excluded, the linear regression demonstrated a correlation coefficient of 5.5 degrees phase difference per degree Celsius, with an R2 = 0.84. In both phantom and human treatments, temperature measured via corrected phase difference closely tracked measurements obtained with fiberoptic probes during the hyperthermia treatments. CONCLUSIONS: Proton chemical shift imaging with current MRI and hyperthermia technology can be used to monitor and control temperature during treatment of large tumors in the distal lower extremity.

Adult↗

PubMed1985

Determination of the peak power output during maximal brief pedalling bouts.

The purpose of this study was to propose an optimization procedure for determining power output during very brief maximal pedalling exercise. Twenty-six healthy male students (21-28 years) performed anaerobic tests on a Monark bicycle ergometer with maximal effort for less than 10 s at eight different loads ranging from 28.1 to 84.2 Nm in pedalling moment. The maximal pedalling rate was determined from the minimal time required for one rotation of the cycle wheel. Pedalling rate decreased linearly with the load. The relationship between load and pedalling rate was represented by two linear regression equations for each subject; one regression equation was determined from eight pairs of pedalling rates and loads (r less than -0.976) and the other from three pairs (at 28.1, 46.8, 65.5 Nm; r less than -0.969). The two regression coefficients of the respective regression equations were almost identical. Mean +/- S.D. of maximal power output (Pmax) which was determined for each subject based on the two linear regression equations for eight pairs and three pairs of pedalling rates and loads was 930 +/- 187 W (13.4 +/- 1.6 W kgBW-1) and 927 +/- 187 W (13.4 +/- 1.6 W kgBW-1), respectively. There was no statistically significant difference between the values of Pmax which were obtained from each equation. It was concluded that maximal anaerobic power could be simply determined by performing maximal cycling exercise at three different loads.

Anaerobiosis↗

PubMed2006

Sleep duration and overweight among Australian children and adolescents.

AIM: To examine the association between sleep and overweight and waist circumference (WC) in children and adolescents. METHODS: Data were from a nationally representative sample of 6324 7-15-y-old males and females from the Australian Health and Fitness Survey. Associations between sleep duration and body mass index (BMI) and WC were examined by analysis of covariance, linear regression, and logistic regression. RESULTS: In the total sample, there was a significant main effect across sleep-duration categories ( or=10 h) for BMI. Linear regression showed significant age, sex, age-sleep, and age-sex-sleep interactions in the total sample. There was an inverse graded relationship between sleep and BMI and WC in boys. In boys, there was a 1.6-1.8 times greater odds of overweight for those who reported 8-9 h or 9-10 h of sleep compared to those reporting>or=10 h of sleep. For boys reporting or=10 h of sleep. In contrast, no significant associations between sleep and overweight were found in girls. CONCLUSION: Sleep duration was inversely related with overweight in young males but not females.

Adolescent↗

PubMed1981

How good are the numbers for cigarette tar at predicting deliveries of carbon monoxide, hydrogen cyanide, and acrolein?

Simple and multiple linear regression analyses were performed on the tar, nicotine, CO, HCN, and acrolein deliveries of 98 brands of commercially available Canadian cigarettes. Simple linear regressions of CO, HCN, and acrolein on tar and of acrolein on CO were not significant at the 5% level for plain cigarettes; all other regressions were very strongly significant (p less than 0.01). In addition there was strong statistical evidence that filter, vented filter, and plain cigarettes have different regression relations and different levels of precision associated with the regression parameters. With respect to CO, tar level could predict the corresponding CO value only within 3.9 mg (filter), 1.9 mg (vented filter), and 3.1 mg (plain). These results show that tar delivery alone is an inadequate predictor of gas-phase constituents such as CO. Information concerning these constituents is best conveyed by an analytically determined value for each component.

Acrolein↗

PubMedDate not supplied

M-mode echocardiographic ratio indices in normal dogs, cats, and horses: a novel quantitative method.

A novel method for quantitative echocardiographic interpretations is introduced based on the calculation of ratio indices in which each raw M-mode measurement is divided by the aortic root dimension (Ao). "Aorta-based" indices were calculated with the animal's measured aortic root dimension (Ao(m)) as the length standard. Conversely, "weight-based" indices employed an idealized estimate of aortic dimension (Ao(w)) with a weighted least squares linear regression against the cube root of body weight (Ao(w) = kW(1/3)). Use of these indices circumvented undesirable statistical characteristics inherent in linear regression of echocardiographic dimensions against body weight and, to a lesser extent, body surface area. Compared with the regressions, ratio indices resulted in substantial refinement of the predictive range for each M-mode measurement in dogs, particularly with decreasing body size. Weight-based indices outperformed aorta-based indices in this regard. To refine the predictive range, neither type of index was clearly advantageous in cats compared with the simple average method typically employed for that species. Several of the raw M-mode measurements, however, were correlated with body weight in cats and horses, indicating the need for an appropriate correction for body size in these species. The ratio index method was suitable for this purpose. Summary statistics derived from normal dogs (n = 53), cats (n = 32), and horses (n = 17) are presented for each index, including novel clinical indices calculated from area ratios. The latter were designed to represent body size-adjusted lett ventricular stroke area (ie, volume overload) and myocardial wall area (ie, hypertrophy).

Animals↗

PubMed1988

Blood oxygen content estimated from PO2, PCO2, and pH.

Oxygen content of blood (265 samples, 25 dogs) from two experimental groups was estimated from measurements of blood PO2, PCO2, pH, hemoglobin, and body temperature with the computational subroutines of Olszowka and Farhi (6). Each computed value was compared with the corresponding oxygen content measured directly by a galvanometric oxygen fuel cell (Lex-O2-Con analyzer). The computed values had consistent errors when compared with the corresponding fuel cell determinations. Linear regression of fuel cell determinations on the corresponding computed values was used to obtain a corrected estimate of oxygen content. When the linear regression correction procedure was performed within each of 25 dogs, the resultant estimates were substantially improved over a lumped correction. The mean absolute value of the difference between the corrected calculated value within an individual dog and the corresponding oxygen fuel cell content determination was 0.38 +/- 0.28 (6 anesthetized dogs, 76 samples) and 0.17 +/- 0.15 (19 awake dogs, 189 samples) (SD) vol% for the two experimental groups. It is concluded that blood oxygen content may be accurately estimated from PO2, PCO2, and pH when appropriately corrected. The advantage is that only a small subset of the total number of blood samples needs to be analyzed with the oxygen fuel cell.

Animals↗

PubMedDate not supplied

Gallbladder volume in adults and its relationship to age, sex, body mass index, body surface area and gallstones. An epidemiologic study in a nonselected population in France.

BACKGROUND/AIMS: The role of a large gallbladder volume with regard to a predisposition for gallstones is unknown. It is possible that an increase in gallbladder volume could result in impaired gallbladder motility and bile stasis. We looked for factors affecting gallbladder volume in a random population in the southeast of France. METHODS: To assess the relationship between gallbladder volume and gallstones, 528 subjects over the age of 30 were studied (72 with lithiasis). Age, sex, body mass index, body surface area and gallbladder volume were collected for each subject. A linear regression analysis was performed to look for significant variables. RESULTS: The overall adjusted prevalence of cholelithiasis was 13.9% in our population. On linear regression analysis, two variables (age and surface area) were found to be independently correlated with gallbladder volume. Gallbladder volume was significantly increased in subjects over 50 years (p < 0.001). There was a positive correlation between gallbladder volume and body surface area (r = 0. 33, p < 0.001). In this study, the presence or absence of gallstones did not significantly affect the gallbladder volume. CONCLUSIONS: We report that there is dilatation of the gallbladder with age and with an increase in body surface area. Whether this could represent risk factors for the occurrence of gallstone remains uncertain.

Adult↗

PubMed1993

Relationship between mean arterial pressure and parameters derived from blood flow velocity waveforms in the systemic circulation of fetal sheep.

In 8 fetal sheep under anesthesia, we examined the relationship between the fetal aorta blood flow velocity waveform and fetal mean arterial pressure after administration of norepinephrine and angiotensin II. It was hypothesized that the pulsatility index (PI) of the waveform would change during fetal hypertension. Measurements were performed using a 20-MHz Doppler transducer on the aorta directly beneath the diaphragm and a catheter inserted via the femoral artery into the abdominal aorta. Further instrumentation included a Doppler transducer and an electromagnetic flowmeter on the common umbilical artery and a catheter in the inferior vena cava. Fetal hypertension was induced by bolus administration of either norepinephrine or angiotensin II or by infusion of norepinephrine. With the Doppler transducer on the common umbilical artery, it was possible to study external iliac artery blood velocity waveforms in 4 fetal lambs, whereas aorta blood velocity waveforms were recorded in 7 fetal lambs. The measurements of external iliac artery PI and mean arterial pressure were characterized by a linear regression with a correlation coefficient of 0.72, whereas the measurements of aorta PI and mean arterial blood pressure were characterized by a linear regression with a correlation coefficient of 0.40. However, notable changes were observed in the aorta blood velocity waveform, which were not expressed by a substantial increase in the aorta PI. These changes can be described as a narrowing of the systolic peak and an earlier occurrence of the first dicrotic notch.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin II↗

PubMed2002

Multicenter study of the LCx HIV RNA quantitative assay--a new competitive reverse transcriptase-PCR which targets pol genomic region of HIV-1 for the measurement of type B, non-type B and group O HIV-1 RNA.

Performance characteristics of the Abbott LCx HIV RNA Quantitative Assay (LCx HIV) were established in a multicenter study comparing it with the manual (Amplicor v1.5) and automated (Cobas) ultra-sensitive Roche Amplicor HIV-1 Monitor v1.5, the Bayer Quantiplex HIV RNA 3.0 (bDNA v3.0), and the Organon NucliSens HIV QT 2.0 (NucliSens). Within-run precision of LCx HIV assessed in clinical specimens was SD log10 0.210 at approximately 50 copies/ml, and log10 0.133 at approximately 400 copies/ml. Total precision in a reconstituted type B HIV-1 RNA panel was SD log10 0.380 at 100 copies/ml, and SD log10 0.180 at 1000 copies/ml. Type B HIV-1 RNA sensitivity (1 ml input) assessed at a 50%, 75% and 95% detection rate ranged from 29 to 41, 54 to 75 and 94 to 176 copies/ml, respectively. Overall specificity in HIV seronegative individuals was 99.78%. Linear regression indicated close assay correlations and agreements for measurement of type B HIV-1 RNA. Pearson's correlations and (Log10LCx=aLog10x + b) linear regressions were 0.91 (y=0.892 Log10Amplicor + 0.595), 0.93 (y=0.827 Log10Cobas + 0.969), 0.93 (y=0.951 Log10bDNA + 0.550), and 0.79 (y=0.834 Log10NucliSens + 0.911). LCx HIV was least affected by the genetic variability of HIV-1. LCx HIV detected 99% of non-type B HIV-1 group M samples (subtypes A-G), Amplicor v1.5 detected 96%, and bDNA v3.0 detected 99%. The assays detected 10/11, 1/11 and 8/11, respectively of the HIV-1 group O samples. LCx HIV vs. Amplicor/bDNA Spearman's rank correlations for quantification of non-type B HIV-1 RNA were 0.76/0.84 (A), 0.93/0.93 (C), 0.73/0.99 (D), 0.86/0.98 (E), and 0.40/0.83 (group O). LCx HIV assays consistently detect and quantify type B, non-type B and group O HIV-1 RNA.

Acquired Immunodeficiency Syndrome↗

PubMed2006

Mental ability and psychological work performance in Chinese workers.

This study was to explore the relationship among mental ability, occupational stress, and psychological work performance in Chinese workers, and to identify relevant modifiers of mental ability and psychological work performance. Psychological Stress Intensity (PSI), psychological work performance, and mental ability (Mental Function Index, MFI) were determined among 485 Chinese workers (aged 33 to 62 yr, 65% of men) with varied work occupations. Occupational Stress Questionnaire (OSQ) and mental ability with 3 tests (including immediate memory, digit span, and cipher decoding) were used. The relationship between mental ability and psychological work performance was analyzed with multiple linear regression approach. PSI, MFI, or psychological work performance were significantly different among different work types and educational level groups (p<0.01). Multiple linear regression analysis showed that MFI was significantly related to gender, age, educational level, and work type. Higher MFI and lower PSI predicted a better psychological work performance, even after adjusted for gender, age, educational level, and work type. The study suggests that occupational stress and low mental ability are important predictors for poor psychological work performance, which is modified by both gender and educational level.

Adult↗

PubMed1992

[Dual-energy X-ray absorptiometry of the vertebrae: determining which vertebrae should be scanned].

This study was aimed at verifying whether bone mineral density (BMD) and its loss with aging are different in the lumbar vertebrae and whether the region of interest--which is usually limited to the L2-L4 segment--may be extended to L1-L4. BMD was measured by means of dual-energy X-ray absorptiometry (Hologic QDR 1000) in 74 women, aged 37 to 78 years, not affected with any disease or subjected to any treatment known to interfere with bone metabolism. The relationship between age and BMD was expressed by the following equations for L1, L2, L3: BMD-L1 = 1181.68-7.85 x age, BDM-L2 = 1251.57-7.70 x age, BMD-L3 = 1231.66-6.57 x age, as shown by linear regression analysis. The behavior of the bone density of L4 with age appeared to be different and could not be described by linear regression curves and was therefore not comparable with that of the other vertebrae. BMD was different in the four lumbar vertebrae as shown by: a) the diversity of the intercept of the regression lines describing age-bone density relationships (F = 7.7, p < 0.001); b) the bone density of L1 being lower than the mean bone density of the L2-L4 region (p < 0.005); c) the bone density of L4 being higher than the mean bone density of the L1-L3 region (p < 0.001). In order to evaluate the effect of senile degenerative changes of the vertebrae on the relevant bone density, two groups of women were considered, according to age--i.e., pre- or iuxtamenopausal and late postmenopausal. It appeared that the BMD of L1 was always more correlated to the bone density of L2 and L3 than the BMD of L4. Our results suggest that L1 is homogeneous to the L2-L3 region, relative to both bone density and its loss with aging. Therefore, L1 should be included in the region of interest during the examination. Even though the bone mineral content of L4 and its loss with aging seem to be different, our results do not allow the exclusion of L4 from the scanned area.

Absorptiometry, Photon↗

PubMed2006

[Contrast analysis on two air fluorine content measurement methods].

OBJECTIVE: To take the two kinds of sampling and measurement methods of air fluorine content in the endemic fluorosis area to carry on the comparison, understanding their difference and inside relation. METHODS: Sampled 22 households random on the scene in the disease area with two samplers by two methods, at the position of which, at the same time, equidistance, same highness, as close as possible, but not produce interactive effect, to collect 34 of the air sample, and then gained the results by their respective methods of laboratory analysis and statistical analysis. RESULTS: The test of significance between two methods was P > 0.05, the coefficient of correlation was r = 0.7752, the test of significance was P < 0.01, the equation of linear regression between the GB method (X) and the manual method (Y) was Y = 1.1623X + 0.0008, the test of significance of coefficient of regression was P < 0.01. CONCLUSION: Two kinds of methods had no significant differences. They preset the medium degree positive correlation and a linear regression. The air fluoride in different granularity of suspended particles was not the same. The GB method was more applicable to research of synthesis damage towards the exposing crowd in burning coal fluorine, and manual method was more applicable to research of the damage resulting from the exposing crowd in burning coal fluorine through the breath system. Generally speaking, the results of the manual method was higher than the GB method.

Air Pollutants↗

PubMed1991

Height estimation from foot and shoeprint length.

Foot length displays a biological correlation with height that suggests the latter might be estimated from foot- or shoeprints when such evidence provides an investigator the best or only opportunity to gauge that aspect of a suspect's physical description. Previous utilization of percentages and linear regressions of foot length to make height estimates is reviewed and appraised, as is such use of shoeprints. Newly determined percentages and linear regressions for determining height from foot length for young adult males and females based upon very large U.S. Army anthropometric databases are presented and evaluated. Suggestions are made for the practical employment of shoeprint length, preferably as a direct measurement but also indirectly as a shoe size indicator, for height assessment.

Adult↗

PubMedDate not supplied

Use of neural networks in medical diagnosis.

In recent years artificial neural networks have been popular both as a subject for research and as application tools in various domains. In this study, use of a neural network in the prediction of diagnostic probabilities is proposed. When the diagnostic probabilities of insulin-dependent diabetes mellitus were predicted both by linear regression and by a neural network in an empirical experiment, the predictions of the neural network were more accurate than those of linear regression. These results suggest that the use of a neural network should be considered whenever prediction of diagnosis is required.

Bayes Theorem↗