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Biomedical subjects

William D Leslie

Publications and source records attributed to William D Leslie.

At least 19 recordsLinked to original sources
PubMed2007

Variation in heart rate influences the assessment of transient ischemic dilation in myocardial perfusion scintigraphy.

BACKGROUND: Transient arrhythmias can affect transient ischemic dilation (TID) ratios. This study was initiated to evaluate the frequency and effect of normal heart rate change on TID measures in routine clinical practice. METHODS: Consecutive patients undergoing stress/rest sestamibi gated myocardial perfusion scintigraphy were studied (N = 407). Heart rate at the time of stress and rest imaging were recorded. TID ratios were analyzed in relation to absolute change in heart rate (stress minus rest) for subjects with normal perfusion and systolic function (Group 1, N = 169) and those with abnormalities in perfusion and/or function (Group 2, N = 238). RESULTS: In Group 1, mean TID ratio was inversely correlated with the change in heart rate (r = -0.47, P < 0.0001). For every increase of 10 BPM in heart rate change, the TID ratio decreased by approximately 0.06 (95% confidence interval 0.04-0.07). In Group 2, multiple linear regression demonstrated that the change in heart rate (beta = -0.25, P < 0.0001) and the summed difference score (beta = 0.36, P < 0.0001) were independent predictors of the TID ratio. CONCLUSION: Normal variation in heart rate between the stress and rest components of myocardial perfusion scans is common and can influence TID ratios in patients with normal and abnormal cardiac scans.

Journal Article↗
PubMed2007

Changes to osteoporosis prevalence according to method of risk assessment.

UNLABELLED: The impact of clinical risk factor-based absolute risk methods on the prevalence of high risk for osteoporotic fracture is unknown. We applied absolute risk methods to 6646 subjects and found that the prevalence of elderly women deemed to be at high risk increased substantially, whereas the overall prevalence was highly dependent on the threshold used to designate high risk. INTRODUCTION: Many groups have advocated using absolute risk methods that incorporate clinical risk factors to target patients for osteoporosis therapy. We examined how the application of such absolute risk classification systems influences the prevalence of those considered to be at high risk for osteoporotic fracture and compared these systems to one based solely on BMD. MATERIALS AND METHODS: Using 6646 subjects from the Canadian Multicentre Osteoporosis Study (CaMos), a prospective, randomly selected, population-based cohort, we assessed three different systems for determining prevalence of high risk for osteoporotic fracture: a BMD-based system; a simplified risk factor system incorporating age, sex, BMD, and two clinical risk factors; and a comprehensive system, incorporating age, sex, BMD, and seven clinical risk factors. The 10-year absolute risks of incident fragility fracture were compared across systems using three different high-risk thresholds. RESULTS: The prevalence of a T score < or = -2.5 was 18.8% (95% CI: 17.7-19.9%) in women and 3.9% (95% CI: 3.0-4.7%) in men. Using a 15% 10-year risk of fracture threshold, the prevalence of women at high risk increased to 46.9% (95% CI: 45.4-48.4) and 42.5% (95% CI: 41.1-43.9) when the comprehensive and simplified risk factor classification systems were used, respectively. Using a 25% 10-year absolute risk threshold, the prevalence of high risk was similar to that of the BMD-based system, whereas the 20% threshold gave intermediate rates. All thresholds analyzed resulted in an increased prevalence of older women at high risk for fracture, whereas only the 15% 10-year risk of fracture threshold resulted in an increase in the prevalence of men at high risk. CONCLUSIONS: The application of risk factor-based systems results in an increased prevalence of older women at high risk. The prevalence of individuals at high risk may increase with changes to the methods used to determine those who are eligible for therapy. These data have important implications for the pattern of care and costs of treating osteoporotic fractures.

Absorptiometry, Photon↗
PubMed2007

Number of osteoporotic sites and fracture risk assessment: a cohort study from the Manitoba Bone Density Program.

UNLABELLED: Site-discordance in BMD assessment is common and significantly affects patient categorization. Greater number of osteoporotic sites correlates with lower T scores at each index site. This largely explains the positive association between number of osteoporotic sites and fracture risk. INTRODUCTION: Site-discordance in BMD is common when used to classify patients based on a cut-off T score of -2.5. It is unclear whether fracture risk assessment is improved by considering BMD information from multiple sites. Our objective was to assess the contribution of number of osteoporotic sites to overall fracture risk. MATERIALS AND METHODS: The study population was drawn from the regionally based clinical database of the Manitoba Bone Density Program that includes all clinical DXA test results for the Province of Manitoba, Canada. Analyses were limited to 16,505 women>or=50 years of age at the time of baseline DXA of the spine (L1-L4) and hip (three sites). During follow-up (3.2+/-1.5 years), longitudinal health service records showed 765 women with at least one osteoporotic fracture code (hip, forearm, spine, or humerus). RESULTS: Of 5012 women classified as osteoporotic by at least one site (T score -2.5 or lower), almost one half (2370; 47%) were abnormal at only a single site. Among the 1856 women with an osteoporotic total hip measurement, mean total hip T scores decreased as the number of additional osteoporotic sites increased (-2.58, no other osteoporotic sites; -2.69, one other site; -2.87, two other sites; -3.17, three other sites; Spearman r=-0.44, p<0.0001). Age-adjusted fracture risk from a Cox proportional hazards model increased as the number of osteoporotic sites increased (p<0.0001), but number of osteoporotic sites was no longer an independent predictor after total hip BMD was included as a covariate (p=0.19). Covariate adjustment for other sites of BMD measurement attenuated, but did not eliminate, the effect of number of osteoporotic sites. CONCLUSIONS: Site-discordance is common and significantly affects patient categorization when different skeletal sites are used for diagnosis. Greater number of osteoporotic sites correlates with lower T scores at each index site. This largely explains the positive association between number of osteoporotic sites and fracture risk.

Absorptiometry, Photon↗
PubMed2006

Clinical risk factors for fracture in postmenopausal Canadian women: a population-based prevalence study.

Clinical risk factor assessment can be used to enhance fracture risk estimation based upon bone densitometry alone. Population- and age-specific risk factor prevalence data are required for the construction of these risk models. Our objective was to derive population-based prevalence estimates of specific clinical risk factors for postmenopausal women resident in the Province of Manitoba, Canada. A random sample of 40,300 women age 50 or older identified from the provincial health plan was mailed a validated self-report risk factor survey. The response rate was 8747 (21.7%) with a final study population of 8027 women after exclusions. The individual prevalence for each clinical risk factor ranged from 5.8% for hyperthyroidism to 33.0% for a fall in the preceding 12 months. Most point prevalence estimates were similar to other large cohort studies, though the prevalences of inactivity and poor mobility were higher than expected while height at age 25 and the prevalence of any fracture after age 50 were lower than expected. Most of the respondents (86.9%) had at least one non-age clinical risk factor, 60.6% had two or more, and 33.5% had three or more. Age affected risk factor prevalence, and older age was associated with a higher rate of multiple risk factors. The availability of age-specific risk factor prevalence rates in this population may allow for more accurate fracture risk modeling.

Aged↗
PubMed2006

Striatal function in generalized social phobia: a functional magnetic resonance imaging study.

BACKGROUND: Although evidence suggests the involvement of the amygdala in generalized social phobia (GSP), few studies have examined other neural regions. Clinical, preclinical, and dopamine receptor imaging studies demonstrating altered dopaminergic functioning in GSP suggest an association with striatal dysfunction. This is the first functional magnetic resonance imaging (fMRI) study to use a cognitive task known to involve the striatum to examine the neural correlates of GSP. We examined whether subjects with GSP had differential activation in striatal regions compared with healthy control subjects while engaged in a cognitive task that has been shown to activate striatal regions reliably. METHODS: Ten adult, unmedicated subjects with a primary DSM-IV diagnosis of GSP and 10 age-, gender-, and education-matched healthy comparison subjects underwent fMRI while performing the implicit sequence learning task. RESULTS: The GSP and healthy comparison subjects did not differ significantly on the behavioral performance of the task. Subjects with GSP, however, had significantly reduced neural activation related to implicit learning compared with healthy comparison subjects in the left caudate head, left inferior parietal lobe, and bilateral insula. CONCLUSIONS: These findings support the hypothesis that GSP is associated with striatal dysfunction and further the neurobiological understanding of this complex anxiety disorder.

Adult↗
PubMed2006

Effectiveness of bone density measurement for predicting osteoporotic fractures in clinical practice.

CONTEXT: Bone density measurement with dual-energy x-ray absorptiometry is widely used for fracture risk assessment. It has not been established that published gradients of fracture risk from study populations can be directly applied to clinical populations. OBJECTIVE: The objective of the study was to assess osteoporotic fracture prediction with dual-energy x-ray absorptiometry in a large clinical cohort. DESIGN: This was a historical cohort study (mean observation period 3.2 +/- 1.5 yr). PATIENTS: The study population was drawn from the population-based database of the Manitoba Bone Density Program. Analyses were limited to women aged 50 yr or older at baseline (n = 16,505). MAIN OUTCOME MEASURE: Each subject's longitudinal health service record was assessed for the presence of nontrauma fracture codes (hip, spine, wrist, and humerus) after bone density testing. Age-adjusted hazard ratios for fracture were derived from Cox proportional hazards models. RESULTS: Site-specific and overall fracture rates were significantly associated with each site of bone density measurement (all P < 0.00001). The 95% confidence intervals overlapped those from a widely cited metaanalysis of fracture prediction from different sites. Although fracture prediction was not significantly different between the three hip measurement sites, each hip site was better than the lumbar spine for predicting overall fractures (nonoverlapping 95% confidence intervals). The manufacturer sd (equivalent to a unit change in T-score) resulted in a significantly smaller gradient of risk for the spine than when the population sd was used. CONCLUSIONS: Bone density measurements are effective for predicting fractures in clinical practice. However, hip measurements were superior to the spine in overall osteoporotic fracture prediction.

Absorptiometry, Photon↗
PubMed2006

Race/ethnicity and fracture risk assessment: an issue that is more than skin deep.

The study of race/ethnicity in relation to health outcomes and health disparities is of great importance in medicine. This is as true in the field of osteoporosis as it is in others, and it comes into sharp focus when the question of population-specific reference data for bone densitometry arises. Race/ethnicity can be viewed as both an ecosocial construct and as a biomedical concept. Whether or not, and how, to use race/ethnicity in fracture assessment potentially places these two paradigms in opposition. In this article, some of the issues that need to be considered to develop a rational approach to reference data selection and a globally acceptable measure of fracture risk are reviewed. Race/ethnicity is often a proxy for other disease-related risk factors. Understanding fundamental risk factors goes beyond the language of race/ethnicity.

Bone Density↗
PubMed2006

Deficit in schizophrenia to recruit the striatum in implicit learning: a functional magnetic resonance imaging investigation.

In schizophrenia, explicit learning deficits have been well established although it is less clear whether these patients have deficits in implicit learning (IL). IL is thought to depend on intact striatal functioning. This study examined the hypothesis that schizophrenia patients show deficient recruitment of striatal activation during an IL paradigm, relative to performance-matched healthy comparison subjects. Ten subjects with schizophrenia on atypical antipsychotic medication and 10 age, gender, education, and performance matched healthy comparison subjects underwent fMRI while performing an IL task. On the basis of whole-brain and striatal region-of-interest analyses, we found a relative lack of striatal activation in schizophrenia patients. This result is consistent with convergent evidence of striatal dysfunction in schizophrenia.

Adult↗
PubMed2006

Application of the 1994 WHO classification to populations other than postmenopausal Caucasian women: the 2005 ISCD Official Positions.

In 2003, the International Society for Clinical Densitometry (ISCD) developed Official Positions regarding the applicability of the World Health Organization (WHO) classification of bone mineral density to populations other than postmenopausal women. However, these prior Official Positions do not fully address bone mineral density reporting in females prior to menopause, men, and non-whites. During the 2005 ISCD Position Development Conference, members of the ISCD Expert Panel in conjunction with the ISCD Scientific Advisory Committee re-addressed these topics and, based upon stringent reviews of best available data, developed ISCD Official Positions that provide greater specificity and clarification with respect to the following: (1) the utility of the term 'osteopenia'; (2) utilization of T- and Z-scores for bone mineral density reporting; (3) when to apply the WHO densitometric classification; and (4) which normative database(s) should be used for non-white individuals. Briefly, the term "osteopenia" is retained, but 'low bone mass' or 'low bone density' is preferred. Z-scores, not T-scores, are preferred in females prior to menopause and males under age 50. In these individuals, a Z-score of -2.0 or lower is defined as "below the expected range for age" and a Z-score above -2.0 is "within the expected range for age." T-scores are preferred and the WHO classification is applicable for postmenopausal women and men age 50 and older. These Official Positions, rationale and evidence are discussed in the following report.

Absorptiometry, Photon↗
PubMed2006

The impact of bone area on short-term bone density precision.

It has been proposed that bone area on two scans should be very close (within 2%) in order to ensure a valid comparison, but this recommendation has not been critically evaluated. We assessed the importance of bone area in test precision within a regional testing program that maintains a large quality assurance database (208 analyzable scan-pairs). Differences in bone area exceeding the "2% rule" were common (22-46% depending upon site). Scan-pairs that exceeded the 2% rule were associated with significantly greater bone density measurement error for the lumbar spine (p<0.005) and femoral neck (p=0.001), but not the total hip. A simpler "1-cm(2) rule" for the lumbar spine also predicted significantly worse spine precision (p<0.005). In conclusion, differences in bone area are sources of short-term bone density measurement error.

Absorptiometry, Photon↗
PubMed2006

Prognostic utility of sestamibi lung uptake does not require adjustment for stress-related variables: a retrospective cohort study.

BACKGROUND: Increased 99mTc-sestamibi stress lung-to-heart ratio (sLHR) has been shown to predict cardiac outcomes similar to pulmonary uptake of thallium. Peak heart rate and use of pharmacologic stress affect the interpretation of lung thallium uptake. The current study was performed to determine whether 99mTc-sestamibi sLHR measurements are affected by stress-related variables, and whether this in turn affects prognostic utility. METHODS: sLHR was determined in 718 patients undergoing 99mTc-sestamibi SPECT stress imaging. sLHR was assessed in relation to demographics, hemodynamic variables and outcomes (mean follow up 5.6 +/- 1.1 years). RESULTS: Mean sLHR was slightly greater in males than in females (P < 0.01) and also showed a weak negative correlation with age (P < 0.01) and systolic blood pressure (P < 0.01), but was unrelated to stress method or heart rate at the time of injection. In patients undergoing treadmill exercise, sLHR was also positively correlated with peak workload (P < 0.05) but inversely with double product (P < 0.05). The combined explanatory effect of sex, age and hemodynamic variables on sLHR was less than 10%. The risk of acute myocardial infarction (AMI) or death increased by a factor of 1.7-1.8 for each SD increase in unadjusted sLHR, and was unaffected by adjustment for sex, age and hemodynamic variables (hazard ratios 1.6-1.7). The area under the ROC curve for the unadjusted sLHR was 0.65 (95% CI 0.59-0.71, P < 0.0001) and was unchanged for the adjusted sLHR (0.65, 95% CI 0.61-0.72, P < 0.0001). CONCLUSION: Stress-related variables have only a weak effect on measured sLHR. Unadjusted and adjusted sLHR provide equivalent prognostic information for prediction of AMI or death.

Journal Article↗
PubMed2006

The importance of spectrum bias on bone density monitoring in clinical practice.

Spectrum bias can occur if a diagnostic test is applied to a patient population of different disease severity than was used in the original test validation. Despite recommendations that bone mineral density (BMD) precision and follow-up assessment be based upon absolute measurements (in g/cm(2)), the use of relative change (in percent) is still frequently encountered. The current study was undertaken to compare absolute and relative precision and change in bone mineral density (BMD) categorization for lower and higher BMD ranges. Patients with baseline and follow-up BMD measurements (1,317 spine pairs and 1,259 hip scan pairs) were identified in the population-based Manitoba Bone Density Program database (1994-2002). Relative (percent) and absolute (g/cm(2)) least significant change (LSC) limits were from a convenience sample from the same population (198 spine scan pairs and 193 hip scan pairs). The main outcome measure was the fraction with BMD change exceeding LSC limits. BMD range strongly affected change category using a pooled relative LSC (lower 33.5% versus higher 20.0%, P < 0.0001) but a range-concordant LSC eliminated this difference (lower 28.3% versus higher 27.1%, P > 0.2). Categorization according to absolute LSC showed no significant difference between lower and higher BMD range patients (27.8% versus 23.4%, P = 0.13). Similar results were seen for the total hip. Disagreement in categorizing spine change occurred in 13.6% (95% CI 11.7-15.4%) using relative LSC but only 1.7% (95% CI 1.0-2.4, P < 0.00001) using absolute LSC. Similar disagreement was seen for the hip (relative LSC 14.0% [95% CI 12.1-15.9%] versus absolute LSC 3.1% [95% CI 2.1-4.1%]; P < 0.00001). In conclusion, spectrum bias was observed when BMD monitoring was based upon relative change (in percent) rather than absolute measurements (g/cm(2)). Categorization of change based upon absolute change in BMD is strongly preferred in the routine clinical setting.

Absorptiometry, Photon↗
PubMed2006

The scintigraphic appearance of de Quervain tenosynovitis.

PURPOSE: The purpose of this study is to describe the scintigraphic pattern of de Quervain tenosynovitis, a common inflammatory condition of the thumb tendon sheaths related to repetitive use. MATERIALS AND METHODS: The author conducted a retrospective audit of consecutive cases with independent clinical validation of the final diagnosis. RESULTS: There were 7 cases of clinically confirmed de Quervain tenosynovitis. The typical scintigraphic finding was a focal area of superficial linear hyperemia and skeletal uptake along the radial aspect of the distal radius corresponding to the anatomic location of the abductor pollicis longus and extensor pollicis brevis. All cases showed an abnormality on at least one phase of the bone scan. CONCLUSIONS: Bone scanning appears to be of value in the differential diagnosis of dorsolateral wrist pain when clinical findings are nondiagnostic. The scintigraphic appearance of de Quervain tenosynovitis can help to confirm the diagnosis while excluding other causes of wrist pain. Determining the sensitivity and specificity of this pattern will require further research.

Adult↗
PubMed2005

Socioeconomic status and the utilization of diagnostic imaging in an urban setting.

BACKGROUND: In publicly funded health care systems, the utilization of health care services should be equitable, irrespective of socioeconomic status (SES). Although the association between SES and health care utilization has been examined in Canada relative to surgical, cardiac and preventive health care services, no published studies have specifically explored the association between SES and diagnostic imaging. METHODS: We examined over 300,000 diagnostic imaging claims made in the Winnipeg Regional Health Authority between Apr. 1, 2001, and Mar. 31, 2002. Using patient postal codes, we assigned SES on the basis of average household incomes in Canada's 1996 census. Using multiple regression, we examined the association between income quintile, patient age group (< or =16, 17-64, > or = 65 years), patient morbidity level according to the Johns Hopkins University Adjusted Clinical Group method (high, moderate, low), and imaging modality (general radiology, vascular, computed tomography, magnetic resonance, and general and obstetric ultrasound). RESULTS: Relative rates (RR) of diagnostic imaging utilization (highest v. lowest income quintile) were significantly increased in pediatric and adult patient groups at all morbidity levels receiving general radiology (highest RR 2.47, 95% confidence interval [CI] 2.07-2.93); pediatric and adult patient groups at high and low morbidity levels and elderly patient groups at low morbidity levels receiving general ultrasound (highest RR 2.26, 95% CI 1.20-4.26); pediatric and adult patient groups at all morbidity levels and elderly patients at high and moderate morbidity levels receiving magnetic resonance imaging (highest RR 2.51, 95% CI 1.78- 3.52); and adult patient groups at all morbidity levels receiving computed tomography (highest RR 1.46, 95% CI 1.35- 1.59). A lower RR of diagnostic imaging utilization in the highest income quintile was found only among patients receiving obstetric ultrasound (RR 0.80, 95% CI 0.73-0.87). No significant associations were found among elderly patients receiving general radiology or computed tomography or adult patients receiving vascular imaging. INTERPRETATION: We found a pattern of increased diagnostic imaging utilization in patient groups with a higher SES. Further research is needed to better understand the nature of this finding and how it contributes to health outcomes.

Adolescent↗
PubMed2005

The role of the striatum in implicit learning: a functional magnetic resonance imaging study.

Previous research has posited striatal involvement in implicit learning. However, imaging studies have not directly compared learners with non-learners. Using functional magnetic resonance imaging with 15 study participants, we used an implicit learning task previously associated with striatal recruitment. Dorsal and ventral striatum activation was observed in the eight participants who demonstrated implicit learning. Ventral striatum activations occurred to a greater extent in implicit learning versus non-implicit learning participants, and were correlated with the degree of reaction time advantage in implicit learning participants, even after controlling for general decreases in reaction time over time. These findings strengthen the specificity of the striatum in implicit learning and are suggestive of a dissociation of striatal regions relative to elements of implicit learning performance.

Adolescent↗
PubMed2005

The impact of hip subregion reference data on osteoporosis diagnosis.

Manufacturers of bone densitometry devices have been moving from manufacturer-specific reference values to data derived from larger population-based cohorts such as the National Health and Nutrition Evaluation Survey (NHANES) III. One bone densitometer manufacturer has released software that provides hip subregion T-score calculations based upon four slightly different versions of hip reference data. Our aim was to determine how changes in hip reference data affect diagnostic classification based on minimum T-scores in older women. We extracted results for lumbar spine and hip bone density measurements from the Manitoba Bone Density database for women aged 50 years or older who had baseline scans on the manufacturer's equipment (n=17,053). T-scores were calculated using manufacturer-specific non-NHANES data and three software implementations of NHANES reference data. One software version gave results at subregions of the hip that were significantly lower than with the three other sets of reference data from the same manufacturer (mean femoral neck T-score absolute difference 0.23-0.48, P<0.00001; mean trochanter T-score absolute difference 0.49-0.70, P<0.00001). As a result the proportion of measurements with a T-score of -2.5 or lower almost doubled at the femoral neck (14.3 versus 27.7%, P<0.00001) and approximately tripled at the trochanter (8.1 versus 24.0%, P<0.00001). The final patient classification of osteoporosis based on a minimum T-score of -2.5 or lower from all four measured sites differed significantly between the four versions (absolute difference 7.9 to 10.4%, P<0.00001). Small changes in the reference data used in T-score calculations had large effects on patient categorization and the calculated prevalence of osteoporosis. The impact of changes in reference data need to be carefully evaluated by users and manufacturers before widespread clinical dissemination.

Absorptiometry, Photon↗
PubMed2005

Prognostic value of lung sestamibi uptake in myocardial perfusion imaging of patients with known or suspected coronary artery disease.

OBJECTIVES: We sought to determine whether lung uptake of technetium-99m (99mTc)-based myocardial perfusion tracers predicts cardiac events. BACKGROUND: Increased lung uptake of thallium-201 during myocardial perfusion scintigraphy can predict important clinical outcomes. It is unclear whether lung uptake of 99mTc-based myocardial perfusion tracers can be used in a similar way. METHODS: Stress lung-to-heart ratio (sLHR) was determined in 718 patients undergoing 99mTc-sestamibi single-photon emission computed tomographic stress imaging. The primary outcome was acute myocardial infarction or death. RESULTS: During a mean follow-up of 5.6 years, a primary end point occurred in 114 patients (16%). The sLHR was significantly greater in those with an adverse outcome (p < 0.00001). The likelihood of an adverse outcome increased by a factor of 1.5 (95% confidence interval 1.2 to 1.7) for each standard deviation increase in sLHR after adjustment for all other variables. The sLHR provided a small but significant improvement in risk stratification when added to clinical, stress test, perfusion, and left ventricular volume information (global chi-square 168.6 vs. 150.7, p < 0.00001). CONCLUSIONS: Stress LHR is an adjunctive prognostic measure in patients with known or suspected coronary artery disease.

Aged↗