Search PubMed⌕ Search

Biomedical subjects

C C Chow

Publications and source records attributed to C C Chow.

At least 73 records · Page 4Linked to original sources
PubMed1998

The reproducibility and usefulness of the oral glucose tolerance test in screening for diabetes and other cardiovascular risk factors.

We examined the reproducibility of oral glucose tolerance tests (OGTT) using the World Health Organization criterion in 212 Chinese subjects (male 149, female 63) who underwent two 75 g OGTTs within a 6-week period. The overall reproducibility was 65.6% (139/212) of which 74 subjects had normal glucose tolerance, 24 had diabetes and 41 had impaired glucose tolerance (IGT) on two occasions. The subjects were divided into three groups [group 1: normal OGTTs on both occasions (n = 74); group 2: one abnormal OGTT (either diabetes or IGT (n = 51); group 3: 2 abnormal OGTTs (n = 87)]. Subjects in group 1 were younger, had lower blood pressure, body mass index (BMI), waist-to-hip ratio (WHR), fasting and 2 h plasma insulin levels, triglyceride, very-low density lipoprotein and apolipoprotein-B concentrations than both groups 2 and 3. Group 2 had similar characteristics as group 3 except for a lower glycated haemoglobin (HbA1c), fasting and 2 h plasma glucose during the two OGTTs. With receiver operating characteristic curve (ROC) analysis, a HbA1c of 5.3% gave an optimal sensitivity of 70.7% and specificity of 74.3% to predict diabetes as defined by a 2 h plasma glucose value > or = 11.1 mmol/L in the first OGTT. Of the 212 subjects, 73 had HbA1c > or = 5.3%. The reproducibility of OGTT was 56.2% for these 73 subjects. With ROC analysis, a BMI of 25 kg/m2 gave an optimal sensitivity of 53.7% and specificity of 56.7% to predict diabetes. For the 36 subjects with BMI > or = 25 kg/m2, the reproducibility of OGTT was 58.3%. Similarly, for the 140 subjects with WHR > or = 0.9, the reproducibility of OGTT was 57.9%. These findings confirmed the poor reproducibility of OGTT which was not improved even amongst subjects with high HbA1c, BMI or WHR. Furthermore, subjects with one abnormal OGTT, whether reproducible or not, had a higher cardiovascular risk profile compared to subjects who had two normal OGTTs.

Adult↗
PubMed1998

Antibodies to glutamic acid decarboxylase in young Chinese diabetic patients.

Antibodies to glutamic acid decarboxylase (GAD) are a useful autoimmune marker for type 1 diabetes mellitus in Caucasians. We examined antibodies to GAD and their relationships with clinical features and pancreatic beta cell function in 140 young Chinese diabetic patients. Over an 18-month period beginning in 1995, 140 young Chinese diabetic subjects with age of onset of disease < or = 35 years and age < 40 years were recruited consecutively, irrespective of their modes of presentation. Clinical features, antibodies to GAD and pancreatic beta cell function (using a glucagon stimulation test) were examined. Increased levels of antibodies to GAD (> 18 units) were detected in 12.1% (n = 17) of these subjects. Forty-three (31%) patients had a classical type 1 presentation and 65 (46%) patients were insulin-deficient based on post-glucagon plasma C-peptide levels. Patients who were insulin-deficient and had a type 1 presentation had the highest prevalence of antibodies to GAD (29.0%) compared with patients who had a type 2 presentation and were non-insulin deficient (6.4%, P = 0.003). Patients who had antibodies to GAD had lower body mass index and waist-hip ratio, earlier onset of disease, lower blood pressure, plasma triglyceride and C-peptide, and higher concentrations of plasma high-density lipoprotein cholesterol and glycated haemoglobin, and were more likely to require drug treatment, compared with those without antibodies to GAD. In conclusion, there was a low prevalence of antibodies to GAD in Chinese young diabetic patients although such antibodies remained a relatively specific marker for insulin deficiency and acute presentation. Causes other than autoimmunity should be sought to explain the high prevalence of insulin deficiency in these young Chinese patients.

Antibodies↗
PubMed1998

Effects of lithium therapy on bone mineral metabolism: a two-year prospective longitudinal study.

Many studies showed an increased occurrence of primary hyperparathyroidism during lithium therapy. We studied 53 patients receiving lithium therapy prospectively for 2 yr. Serum PTH levels were unequivocally elevated. The baseline PTH level was 2.8 +/- 1.2 pmol/L and increased progressively to 3.9 +/- 1.5 pmol/L after 2 yr (P < 0.0005). There was no change in serum calcium, alkaline phosphatase, inorganic phosphate concentrations or tubular reabsorption of phosphate in relation to glomerular filtration rate. Fasting urinary reabsorption of calcium increased significantly (P < 0.0005), which was concordant with the PTH change. Fasting and 24-h urinary excretion of calcium decreased significantly (P < 0.0005), suggesting reduced, rather than enhanced, bone resorption as in primary hyperparathyroidism. This may be the main mechanism in maintaining normocalcemia, despite PTH elevation, during lithium therapy.

Adolescent↗
PubMed1998

Dual phase spiral CT in the detection of small insulinomas of the pancreas.

Dual phase contrast enhanced spiral computed tomography (DPSCT) has the potential to improve detection of small insulin secreting islet cell tumours of the pancreas. Seven patients with biochemically proven insulinoma, who had previously undergone a range of negative radiological procedures, were referred for DPSCT. Images of the pancreas were obtained using 3 mm collimation in the arterial and arteriovenous perfusion phase following the rapid injection of contrast medium. Six tumours were localized in seven patients. The six insulinomas identified on DPSCT ranged in size from 6 mm to 18 mm and were located in the uncinate process (2), head (1), neck (2) and body (1). All six tumours were detected in the arterial phase and four in the arteriovenous phase. The four insulinomas detected on both perfusion phases were more conspicuous in the arterial phase in three patients and more conspicuous in the arteriovenous phase in one patient. In conclusion, high resolution arterial phase acquisition of the pancreas is very valuable in the detection of small insulinomas.

Adult↗
PubMed1998

Torsion of intraperitoneal renal transplants: imaging appearances.

OBJECTIVE: Torsion of a renal transplant is a rare complication with nonspecific clinical manifestations. Prompt detection is necessary to allow surgical treatment and to preserve renal function. We describe the radiologic appearances of torsion of intraperitoneal renal transplants in patients who have undergone simultaneous renal and pancreatic transplantation or dual renal transplantation. CONCLUSION: Renal transplant torsion should be suspected when a change in renal axis associated with abnormal perfusion occurs in an intraperitoneal kidney.

Adult↗
PubMed1998

Combined use of a fasting plasma glucose concentration and HbA1c or fructosamine predicts the likelihood of having diabetes in high-risk subjects.

OBJECTIVE: To assess the validity of using fasting plasma glucose (FPG) concentrations in conjunction with HbA1c or fructosamine for the screening of diabetes in high-risk individuals. RESEARCH DESIGN AND METHODS: In this study 2,877 Hong Kong Chinese (565 [19.6%] men; 2,312 [80.4%] women) with various risk factors for glucose intolerance underwent a 75-g oral glucose tolerance test (OGTT) for screening of diabetes. The risk factors included a family history positive for diabetes, a history of gestational diabetes or impaired glucose tolerance, and obesity. RESULTS: Using World Health Organization (WHO) criteria, 1,593 (55.4%) had normal glucose tolerance, 657 (22.8%) had impaired glucose tolerance, and 627 (21.8%) had diabetes. When the 1997 American Diabetes Association (ADA) criteria were applied, 394 (13.7%) had diabetes with an FPG > or = 7.0 mmol/l. Using multiple receiver operating characteristic curve analysis, the paired values of an FPG of 5.6 mmol/l and a HbA1c of 5.5% gave an optimal sensitivity of 83.8% and specificity of 83.6% to predict a 2-h plasma glucose (PG) > or = 11.1 mmol/l. Likewise, the paired values of an FPG of 5.4 mmol/l and a fructosamine level of 235 mumol/l (n = 2,408) gave an optimal sensitivity of 81.5% and specificity of 83.2%. An FPG > or = 5.6 mmol/l and an HbA1c > or = 5.5% was 5.4-fold more likely to occur in diabetic subjects (based on the WHO criteria) compared with nondiabetic subjects. For paired parameters less than these values, the likelihood ratio of this occurring in diabetic subjects was only 0.11. Similarly, an FPG > or = 5.4 mmol/l and a fructosamine > or = 235 mumol/l was fivefold more likely to occur in diabetic subjects than in nondiabetic subjects, with both parameters less than these values having a likelihood ratio of 0.04. Using these paired values as initial screening tests, only subjects who had an FPG > or = 5.6 mmol/l and < 7.8 mmol/l and an HbA1c > or = 5.5% (n = 642) required an OGTT to confirm diabetes, thereby saving 77.7% [(2,877-642)/2,877] of the OGTTs performed. Similarly, only subjects who had an FPG > or = 5.4 mmol/l and < 7.8 mmol/l and a fructosamine > or = 235 mumol/l (n = 526) required OGTT to confirm diabetes, meaning that 78.2% [(2,408-526)/2,408] of the OGTTs could have been saved. Based on the 1997 ADA criterion of an FPG cutoff value of 7.0 mmol/l, the corresponding numbers of OGTTs to be saved were 82.6% and 85.5%, respectively. CONCLUSIONS: The paired values of FPG and HbA1c or FPG and fructosamine helped to identify potentially diabetic subjects, the diagnosis of which could be further confirmed by the 75-g OGTT. Using this approach approximately 80% of OGTTs could have been saved, depending on the diagnostic cutoff value of FPG.

Adult↗
PubMed1997

The effect of age on cardiovascular risk factors in Chinese women.

Chinese women traditionally have a low incidence of coronary heart disease. However, information on cardiovascular risk factors in this population are relatively scarce. We examined these risk factors in 601 Hong Kong Chinese women (age+/-SEM, 38.5+/-0.4 years; range, 18-66 years) stratified into four age groups (group 1, < or =30 years; group 2, 31-40 years; group 3, 41-50 years; group 4, > or =51 years). Increasing age in Chinese women was associated with increased body mass index, waist-to-hip ratio, systolic and diastolic blood pressure, fasting plasma total cholesterol, triglyceride, low-density lipoprotein, apolipoprotein B, fasting and 2-h plasma glucose, glycated haemoglobin, fasting plasma insulin and urate concentrations. After adjustment for body mass index, waist-to-hip ratio and smoking, all these age-related associations remained statistically significant except for fasting plasma insulin concentration. There was a progressive increase with age in the prevalence of glucose intolerance, hypertension, dyslipidaemia and obesity. These prevalence rates further increased in subjects aged 51 years (the mean menopausal age in Asian women) or above. These findings suggest that age had an important and independent effect on cardiovascular risk in Chinese women and that, as in Caucasians, the onset of menopause might further increase this risk.

Adolescent↗
PubMed1997

Plasma fibrinogen concentration in a Chinese population.

Plasma fibrinogen concentration has been shown to be a predictor of major cardiovascular events. Information on plasma fibrinogen amongst Chinese has been scanty. We examined the relationships between plasma fibrinogen concentration and cardiovascular risk factors in 988 chinese subjects who underwent 75 g oral glucose tolerance test for screening for glucose intolerance. The study involved a selected sample with subjects who had an history of gestational diabetes, delivery of big babies (birth weight > or = 4 kg), equivocal plasma glucose concentrations and subjects who were family members of diabetic patients. This was mainly a non-smoking (96.6%), non-drinking (98%) and non-exercising (99%) population of which 87% (n = 855) were female. Among the 988 subjects (age +/- S.D. 36.8 +/- 10.2, range 16-79 years), plasma fibrinogen concentration ranged from 1.40 to 9.90 g/l with a mean of 3.26 +/- 0.93 g/l. On stratification of the subjects into 4 quartiles based on plasma fibrinogen concentrations, we found that increased plasma fibrinogen was associated with older age, higher body mass index (BMI), systolic and diastolic blood pressure (BP), fasting and 2 h plasma glucose (PG), prevalence of diabetes, glycated haemoglobin (HbA1c) and triglyceride (TG) level. After adjustment for age and sex, increased plasma fibrinogen concentration remained associated with higher BMI, systolic BP, 2 h PG and TG level. On multivariate analysis using age, BMI, BP, TG, HbA1c and PG as independent variables, plasma fibrinogen was independently related to plasma TG concentration and HbA1c. With 1 S.D. change in TG concentration and HbA1c, there were 3.7 and 5.2% changes in plasma fibrinogen concentration respectively. These findings emphasize the close relationships between plasma fibrinogen and cardiovascular risk factors, in particular abnormal lipid and glucose metabolism.

Adolescent↗
PubMed1997

Accuracy, precision and user-acceptability of self blood glucose monitoring machines.

The performance of six self-monitoring blood glucose (SMBG) machines (Accutrend, Reflolux S, Companion 2, Glucometer GX, Glucometer IV and One Touch II) were examined using venous blood samples from 88 patients. Whole blood glucose (BG) values were measured by four machines from each brand. Machine-generated whole blood glucose (BG) values were corrected before comparison with laboratory plasma glucose values, measured by a glucose oxidase method. Based on error grid analysis, most of the corrected machine-generated BG values were clinically acceptable. Accutrend, Glucometer IV and Companion 2 showed the greatest consistency between machines of the same brand. Over 80% of corrected BG values generated by Glucometer IV fell within +/-10% of the reference values. One Touch II yielded the most reproducible results with a mean CV of 2.7% and was considered the most user friendly machine. More studies are required to examine the performance of these machines in the hands of patients.

Analysis of Variance↗
PubMed1997

Simple anthropometric indexes and cardiovascular risk factors in Chinese.

OBJECTIVE: Obesity is a major public health problem due to its associations with multiple cardiovascular risk factors. Although there are sophisticated methods, such as imaging, to document total body fat and its distributions, anthropometric measurements remain important in clinical practice. We examined the relationships between cardiovascular risk factors and the three commonest anthropometric measurements for obesity, body mass index (BMI), waist-hip ratio (WHR) and waist circumference (WC), in Hong Kong Chinese subjects. DESIGN AND SETTING: The data are obtained from a prevalence survey for glucose intolerance and lipid abnormality in a representative Hong Kong Chinese working population. All employees from a public utility company and a regional hospital were invited to participate. SUBJECTS: There were 1513 subjects (910 men and 603 women, mean age +/- s.e.m.: 37.5 +/- 0.2 y). All of them had no significant past medical history. MEASUREMENTS: BMI, WHR and WC of the 1513 subjects were assessed for their relationships with various cardiovascular risk factors. These include blood pressure, fasting and 2 h plasma glucose and insulin, glycated haemoglobin, total cholesterol, triglyceride, high density and low density lipoprotein cholesterol, and urine albumin concentration. RESULTS: After age adjustment, all three anthropometric indexes were significantly correlated with the major cardiovascular risk factors in both men and women. When BMI, WHR and WC were analysed according to quartiles, there was a significant trend for blood pressure, plasma triglyceride, fasting and 2 h plasma glucose and insulin to increase, and high density lipoprotein cholesterol to decrease, with increasing obesity after adjustment for age and smoking. Using stepwise regression analysis with the three indexes as independent variables, most of the variance in blood pressure, plasma lipid, insulin, glucose and urinary albumin concentration were explained either by WC or WHR. In women, BMI was the main explanatory variable for reduced high density lipoprotein cholesterol. CONCLUSIONS: In Hong Kong Chinese, BMI, WHR and WC provide important information in assessing cardiovascular risks. In men, central adiposity as reflected by WC and to some extent, WHR, explained most of the variance in blood pressure, plasma glucose, lipid, insulin and albuminuria. In women, all three indexes reflecting general and central obesity contribute to the variance in these risk factors.

Adult↗
PubMed1997

A patient with Graves' disease, thrombocytopenia and chronic hepatitis B.

A 22-year-old Chinese man, a HBsAg carrier, presented with relapse of thyrotoxic Graves' disease complicated by thrombocytopenia and hepatitis. Platelet count and liver enzymes gradually improved following successful treatment of the thyrotoxicosis with radioactive iodine. Possible pathogenetic links and therapeutic implications are discussed.

Adult↗
PubMed1997

Dexfenfluramine in obese Chinese NIDDM patients. A placebo-controlled investigation of the effects on body weight, glycemic control, and cardiovascular risk factors.

OBJECTIVE: To investigate the safety, efficacy, and metabolic effects of dexfenfluramine in obese Chinese NIDDM patients. RESEARCH DESIGN AND METHODS: Thirty-two patients, mean (+/- SD) body weight 76.2 +/- 8.5 kg with corresponding BMI 31.1 +/- 2.1 kg/m2, were randomized into a two-phase study, after a 2-week single-blind run-in period on placebo. Phase 1 was a randomized 3-month double-blind placebo-controlled trial during which either dexfenfluramine or placebo was added to the existing treatment regimens of diet plus or minus sulfonylureas without metformin. Phase 2 was a further 3-month single-blind trial during which the placebo group was given dexfenfluramine without patients' knowledge of changing to active medication, while the active group continued with dexfenfluramine. Body weight, glycemic control, blood pressure, lipids, and quality of life were assessed before and at 3 and 6 months after randomization. A total of 27 patients were also followed for an additional period of 6-12 months (215 +/- 53 days) after dexfenfluramine treatment was withdrawn. RESULTS: During the run-in period, both groups were comparable for all parameters measured. At 3 months, mean changes in BMI were -1.2 +/- 1.0 kg/m2 (dexfenfluramine) vs. -0.1 +/- 0.5 kg/m2 (placebo) (P < 0.001). The mean changes in fasting plasma glucose were -1.14 +/- 0.99 vs. 0.51 +/- 1.34 mmol/l (dexfenfluramine vs. placebo, P = 0.004). HbA(1c) also significantly improved in the dexfenfluramine group (-0.80 +/- 0.53 vs. 0.25 +/- 0.64%, P < 0.001). During the 3-month single-blind dexfenfluramine treatment in the ex-placebo group, there were similar improvements in body weight and glycemic indexes. After cessation of dexfenfluramine therapy at 6 months, significant increases in body weight and glycemic indexes, almost back to the baseline, were observed for both groups. CONCLUSIONS: Dexfenfluramine aids weight loss and improves glycemic control in obese Chinese NIDDM patients over a 3- to 6-month period. These effects are emphasized after withdrawal of treatment and further support the longer-term use of dexfenfluramine for chronic complicated obesity.

Adult↗
PubMed1997

Clozapine: a mimicry of phaeochromocytoma.

OBJECTIVE: To report a case of clozapine-induced hypertension with raised urinary catecholamines. CLINICAL PICTURE: A 27-year-old man fulfilling DSM-III-R criteria for catatonic schizophrenia was treated with clozapine. He later developed both hypertension and raised urinary catecholamines which mimicked phaeochromocytoma. TREATMENT: Clozapine was withdrawn. OUTCOME: Both blood pressure and urinary catecholamines normalised. CONCLUSIONS: Clozapine may induce sympathetic hyperactivity.

Adult↗
PubMed1997

Acromegaly in a woman presenting with diabetic ketoacidosis and insulin resistance.

A 22-year-old Chinese woman presented with typical features of diabetic ketoacidosis. There was a family history of diabetes but she was not obese. Plasma glucose and bicarbonate levels were 27.0 mmol/l and 5 mmol/l, respectively. Significant insulin resistance was noticed: she needed up to 15 units of insulin per hour. She required up to 120 units daily for her diabetic control even after her acidosis had subsided. She was then noticed to have the clinical features of acromegaly. The diagnosis was confirmed, and a cranial CT scan confirmed the presence of a pituitary macroadenoma. She underwent uneventful trans-sphenoidal resection of the tumour and her insulin requirement gradually lessened. Acromegaly should be considered in the differential diagnosis of unexplained insulin resistance.

Acromegaly↗
PubMed1996

Pancreatic beta cell function and antibodies to glutamic acid decarboxylase (anti-GAD) in Chinese patients with clinical diagnosis of insulin-dependent diabetes mellitus.

Antibodies to glutamic acid decarboxylase (anti-GAD) and pancreatic beta cell secretory function were measured in 39 consecutive Chinese patients with a clinical diagnosis of insulin-dependent diabetes mellitus (IDDM) (19 males, mean +/- SD age. 37 +/- 15 years; body mass index (BMI), 22 +/- 4 kg/m2; mean duration of disease, 6.7 +/- 5.6 years). IDDM was defined on the basis of acute symptoms with heavy ketonuria (> 3+) or ketoacidosis at diagnosis, or requirement for continuous insulin treatment within one year of diagnosis. Insulin deficiency was defined as a post-glucagon stimulated plasma C-peptide concentration < or = 0.6 nmol/l. Overall, anti-GAD antibodies were positive (> 18 units) in 23% (n = 9) of these patients. Of the 39 patients, 29 (74%) were insulin deficient and 10 (26%) were non-insulin deficient. Anti-GAD antibodies were positive in 31% of the insulin-deficient patients but in none of the non-insulin-deficient group. Insulin deficiency and anti-GAD positivity were associated with younger age, earlier age of clinical onset and lower BMI. There were independent negative relationships between levels of anti-GAD antibodies and blood pressure and a positive relationship between insulin dosage and albuminuria. This study emphasises the difficulty in differentiating clinically between IDDM and NIDDM in Chinese patients. Despite the acute presentation, these patients had variable pancreatic beta cell secretory function. The varying duration of disease may partly explain the low prevalence of positive anti-GAD antibodies in these patients, but seems unlikely to explain fully the difference from Caucasian IDDM patients.

Adult↗
PubMed1996

Spontaneous action potentials due to channel fluctuations.

A theoretical and numerical analysis of the Hodgkin-Huxley equations with the inclusion of stochastic channel dynamics is presented. It is shown that the system can be approximated by a one-dimensional bistable Langevin equation. Spontaneous action potentials can arise from the channel fluctuations and are analogous to escape by a particle over a potential barrier. The mean firing rate can be calculated using Kramers' classic result for barrier escape. The probability density function of the interspike intervals can also be estimated. The analytical results compare favorably with numerical simulations of the complete stochastic system.

Action Potentials↗