Search PubMed⌕ Search

Biomedical subjects

W J Kalk

Publications and source records attributed to W J Kalk.

At least 19 recordsLinked to original sources
PubMed2005

Effective and accurate screening for diabetic retinopathy using a 60 degree mydriatic fundus camera.

UNLABELLED: OBJECTIVES. To establish whether an experienced endocrinologist could screen accurately for diabetic retinopathy using mydriatic 60 degree fundus photographs compared with a reference standard, viz. the combined highest scores of two experienced ophthalmologists. DESIGN: Retrospective review of 60 degree colour transparency photographs taken over a 6-year period. Retinopathy was graded in a standardised way. SETTING: Patients attending the diabetic clinic at Johannesburg Hospital, South Africa. SUBJECTS: Fifteen hundred and seventeen patients (2446 eyes) formed the basis for the study. Patients were included if there was more than 50% readability of the fundus photographs. OUTCOME MEASURES: Outcome measures were prevalence of any retinopathy and presence of referable (severe) retinopathy. Interobserver agreement was measured using the kappa statistic, and sensitivity and specificity of the screener were evaluated. RESULTS: The prevalence of retinopathy at the clinic was approximately 30%, but only about 12% was severe enough to warrant referral to the ophthalmology outpatient department. The endocrinologist was very accurate in determining cases requiring referral; there was 97% agreement with the reference standard, viz. the combined highest score of two experienced ophthalmologists (gold standard). Correlation on the determination of any retinopathy was less accurate (80% agreement), mostly owing to the endocrinologist reporting more isolated microaneurysms than the ophthalmologists. The screening method used gave a sensitivity of 83% and specificity of 99% which are within recommended standards. CONCLUSIONS: The screening strategy using a mydriatic fundus camera at the diabetic clinic was found to be effective and accurate and greatly reduced the number of possible referrals to the ophthalmology outpatient department.

Adult↗
PubMed2000

Distribution of autoantibodies to glutamic acid decarboxylase across the spectrum of diabetes mellitus seen in South Africa.

AIMS: This study investigated the association between glutamic acid decarboxylase antibodies (GAD-AB) and Type 1, Type 2, pancreatic and lipoatrophic diabetes mellitus (DM) in South African patients. METHODS: Four groups were selected: group A, 100 Black Type 1 DM patients (age at onset < 35 years, body mass index (BMI) < 27 kg/m2 and insulin dependent within 1 year of presentation); group B, 80 Black Type 2 DM patients (age at onset > 35 years, BMI > 27 kg/m2 and controlled on oral hypoglycaemic agents for at least 1 year after presentation); group C, 10 patients of varying ethnicity with DM or impaired glucose tolerance secondary to chronic pancreatitis; group D, five patients of varying ethnicity with DM associated with total lipodystrophy. Fifty healthy Black control subjects were also studied (group E). Serum GAD-AB and random C-peptide levels were measured by radioimmunoassay. RESULTS: Mean C-peptide concentration was significantly lower in Type 1 DM patients than Type 2 DM patients (P < 0.00001). Forty-four patients with Type 1 DM were GAD-AB-positive compared to two patients with Type 2 DM. Two control subjects were also GAD-AB-positive. No patient in the other groups had a titre > 1 U/ml. Type 1 DM patients who were GAD-AB-positive did not differ from those who were GAD-AB-negative for age at onset, duration of DM or C-peptide concentrations. CONCLUSIONS: Auto-immune beta-cell destruction has an important role in the pathogenesis of Type 1 DM amongst African patients. However, Type 2 African DM patients and other diabetes subtypes are largely GAD-AB-negative.

Adult↗
PubMed2000

A survey of hospital outpatient services for chronic diseases in Gauteng.

OBJECTIVES: The rapid evaluation of hospital-based services for chronic non-communicable diseases, in particular aspects of the organisation of services, and indirect indicators of patient care. DESIGN: A postal survey of services for asthma, epilepsy, diabetes and hypertension at nine hospitals. Assessment over 1 week of single blood pressure (BP) and blood glucose readings at the hypertension and diabetes clinics at one regional hospital. SETTING: Nine community and secondary hospitals in Gauteng. RESULTS: Eight hospitals responded. Most did not provide specific clinics for each condition. None of the professional staff had received additional training in chronic disease management, and 7 considered their services to be understaffed. On average, nurses managed 33 patients per day (range 19-50), and doctors 53 (20-80). Mean consultation time was 9 minutes (4-20 minutes). Management guidelines were used for all conditions in 5 hospitals. Modern routine assessments were seldom employed. Estimates of regular patient attendance ranged from 25% to 75%. At the single hospital surveyed, hypertension (N = 233) was controlled in 42.5% of patients using World Health Organisation criteria (BP < 160/95), but in only 24.5% of patients by The Joint National Committee on Prevention, Detection, Evaluation and Treatment of High Blood Pressure (JNC6) standards (BP < 140/90). Random blood glucose was satisfactory (< 10 mmol/l) in 45.2% of diabetic patients (N = 157) while hypertension (N = 100) was well controlled (< 140/90) in 10% of hypertensive diabetic patients. CONCLUSIONS: Services for chronic diseases at non-academic hospitals in Gauteng were characterised by perceived inadequate staff numbers and training, short consultation times, infrequent use of management guidelines and standard assessments, little patient education with regard to self care, and perceived low rates of regular attendance (and hence compliance with medication). At one hospital there was a low rate of hypertension control, and unsatisfactory rates of acceptable glycaemic and BP control among diabetic patients. There is an urgent need for restructuring of services for chronic diseases and for more detailed outcomes research.

Asthma↗
PubMed1998

Thyrotropin receptor antibodies in black South African patients with Graves' disease and their response to medical therapy.

Graves' disease is increasing in incidence amongst urban black South Africans. The pathogenic role of thyrotropin receptor antibodies (TRAb), crucial in other populations, has not been formally evaluated in African communities. We therefore prospectively investigated the prevalence of TRAb in 30 consecutive urban black South African patients with classical Graves' disease at the onset of their illness. This was compared with the frequency of thyroid microsomal and thyroglobulin antibodies in the same patients. Ten patients with euthyroid goitres unrelated to Graves' disease and 10 healthy controls were also studied. Twenty of the hyperthyroid patients were retested 4-6 months after starting carbimazole therapy and ten of them again after 1 year. Initially 83% of patients were positive for TRAb as against 54% for thyroid microsomal and 1 7% for thyroglobulin antibodies. After 4-6 months of treatment, 65% of patients still had elevated (>15% inhibition of binding) TRAb titres, while at 1 year this had dropped to 40% (4 out of 10 patients). All positive patients had relapsed biochemically, while TRAb negative patients were all in remission. We conclude that TRAb are a sensitive and specific marker of Graves' disease in black South Africans and closely parallels the response to medical therapy at 1 year. However, their predictive value for delayed relapse requires the study of a larger cohort of patients over a longer time-frame.

Adult↗
PubMed1998

The management of diabetes at primary level in South Africa: the results of a facility-based assessment.

Diabetes is a widespread condition in South Africa and is often managed at primary level health facilities. This study aimed to assess the quality of diabetes management using a rapid assessment approach, focusing on three indicators as proxy measurements of quality: the regularity of blood glucose level (BGL) measurement; the percentage of patients whose BGLs were within 'acceptable' limits (under 10.0 mmol/l) on at least 75% of visits; the rate at which action was taken in response to high BGLs. Five sites were included in the study, including public and private, doctor- and nurse-based facilities. A total of 128 records were examined. Only 33% of all records were found to be well-managed according to the study criteria. None of the individual facilities were found to have more than 40% of patients achieving BGLs within the study limits. Some obstacles to good glycaemic control were costs to patients, transport problems, a lack of health education and shortcomings in clinical expertise. Policy implications and recommendations are suggested.

Blood Glucose↗
PubMed1998

Iodine deficiency disorders in South Africa.

Iodine is an essential micronutrient, but iodine deficiency remains common worldwide, including many African countries. In South Africa endemic goitre was first noted in the 1920s. Several subsequent surveys have indicated its widespread persistence, despite the limited availability of iodised salt. The significance of nutritional iodine deficiency lies in the associated iodine deficiency disorders, which follow from maternal and fetal hypothyroidism. The extreme consequence is endemic cretinism, but much more prevalent are lesser degrees of intellectual and neurological deficits, with a potential reduction of intelligence scores in affected communities of more than 10%. Such severe consequences of iodine deficiency probably affect a significant proportion of South Africans. The control of iodine deficiency should be easy and inexpensive. Since the December 1995 legislation, all salt manufactured in South Africa must contain potassium iodate. Such supplementation is likely to cause a small increase in auto-immune thyroid disorders. This negative effect is slight in comparison with the potential benefit to millions.

Adult↗
PubMed1998

Dietary iodine deficiency in South Africa. Surveys before the introduction of universal salt iodisation.

OBJECTIVE: To survey iodine nutritional status in several geographically separated communities in South Africa. DESIGN: In an initial study total goitre prevalence (TGP) was correlated with urinary iodine concentration (UIC) in some 300 primary school children in a single district. Thereafter only UIC was surveyed in children from 5 additional communities. RESULTS: In the initial survey in Mpumalanga TGP was 74.2% (23.4% visible) and the median UIC was 15.6 micrograms/l, both data indicating severe iodine deficiency in this district. Median UIC values indicated mild to severe iodine deficiency in districts in the Northern Province, moderate deficiency in the Eastern Cape, and mild deficiency in Soweto, Gauteng. Only non-black African children in Johannesburg were iodine-replete (UIC > 100.0 micrograms/l.) CONCLUSION: Before the introduction of compulsory iodisation of salt in December 1995, dietary iodine deficiency was widespread in South Africa.

Child↗
PubMed1997

Ethnic differences in the clinical and laboratory associations with retinopathy in adult onset diabetes: studies in patients of African, European and Indian origins.

OBJECTIVE: To evaluate the prevalence of diabetic retinopathy (DR) and its associations in adult onset diabetic patients of African, European and Indian origins. DESIGN: The prevalence of retinopathy was determined by 60 degrees retinal photography in 507 consecutive out-patients. Clinical and laboratory associations were evaluated. SETTING: Diabetes clinic in a large community hospital. MAIN OUTCOME MEASURES: The associations between clinical and laboratory measurements with retinopathy. RESULTS: African patients (A) had shorter duration of diabetes (P < 0.001), higher HbA1 levels (P < 0.01) compared to those of Europeans (E) and Indian (I) extraction. A also had lower C-peptide levels (median 0.57 nmol L-1; vs. E. 0.81 nmol L-1 and I, 0.93 nmol L-1) (P < 0.001). The prevalences of retinopathy at diagnosis (21-25%) and overall were similar (A 37%, E 41%, I 37%). Severe DR was more frequent in the Africans (52%, P < 0.0001) and Indians (41%, P = 0.03) compared to the Europeans (26%). In Africans DR was significantly associated only with duration of diabetes (P < 0.0001) and macro-albuminuria (P = 0.01); in I it was also associated with systolic BP (P = 0.03); in E also with lower C-peptide levels (P = 0.0002), worse glycaemic control and greater use of insulin (P < 0.0001). In patients with DR insulin was used less frequently in A (35%) than in E patients (62%) (P = 0.001). CONCLUSIONS: In South Africa, the African population with adult onset diabetes has the highest prevalence of severe retinopathy, probably the result of very poor glycaemic control attributable to more severe insulinopenia and infrequent insulin treatment. Visual loss from diabetic retinopathy is likely to be considerable in Africans.

Adult↗
PubMed1997

Thyroid cancer in South Africa--an indicator of regional iodine deficiency.

OBJECTIVE: Because follicular thyroid cancers predominate in iodine deficient and papillary cancers predominate in iodine-replete populations, we have analysed national and regional (former Transvaal) incidences of these cancer types as a surrogate measure of the population iodine nutritional status in South Africa. DESIGN: Statistical analysis, by race and sex, of differentiated thyroid cancers reported to the South African National Cancer Registry (1988), and of the computerised histology records of the Department of Anatomical Pathology, SAIMR (January 1990 to June 1994; Transvaal data). MAIN OUTCOME MEASURES: Relative frequencies of the two cancer types nationally and geographically in the Transvaal region. MAIN RESULTS: Thyroid cancer was underdiagnosed in populations other than white. Nationally, follicular histology accounted for 55% of all differentiated primary thyroid cancers, and predominated especially in black women. Follicular morphology predominated in blacks resident in the rural regions of the former Transvaal (58%), while papillary histology predominated in urban areas (of present-day Gauteng), irrespective of race (78%; P = 0.003). CONCLUSION: The national predominance of follicular thyroid cancer indicates that significant iodine deficiency exists in the country as a whole. The observed urban-rural differences in prevalences of follicular and papillary cancer types suggest regional differences in the severity of iodine deficiency. There is a need for a formal survey of the population iodine nutritional status in South Africa.

Adult↗
PubMed1996

Screening for diabetic retinopathy in South Africa with 60 degrees retinal colour photography.

OBJECTIVES: Comparison of 60 degrees mydriatic retinal photography, in screening for diabetic retinopathy, with diabetes clinic doctors, formal ophthalmological assessment, and with one or two 45 degrees fields. DESIGN: Consecutive subjects screened by clinicians and photography, and selected eyes evaluated by an ophthalmologist. Randomized photographs assessed through one or two 45 degrees fields (by masking the slides), and at 60 degrees. SETTING: The first 663 patients attending for routine clinic visits and screened for retinopathy. MAIN OUTCOME MEASURES: The relative diagnostic sensitivity of screening methods, the utility of screening one eye only, and the costs of photographic screening. RESULTS: Compared to an ophthalmologist's assessment, retinal photography had a sensitivity of 93% and a specificity of 89% for any retinopathy, and 100 and 75%, respectively, for severe retinopathy. Photography detected 28% more retinopathy (16% severe) than the clinicians. Compared to a 60 degrees field, one 45 degrees field missed 31%, and 2 x 45 degrees fields 11% of retinopathy. Of 57 patients with retinopathy meeting referral criteria, 31 pairs of eyes had substantially discordant scores. The cost of diagnosis in a patient requiring referral to ophthalmologist was about US $37.00. CONCLUSIONS: 60 degrees retinal photography compares well with an ophthalmologists screening, and is better than clinical and one to two 45 degrees field assessments. Both retinae should be screened. This method is cost-effective in our hands.

Diabetic Retinopathy↗
PubMed1996

Habitual exercise attenuates myocardial stiffness in diabetes mellitus in rats.

The effects of regular voluntary (habitual) exercise on left ventricular (LV) diastolic performance, as well as on those hemodynamic, LV geometric and myocardial interstitial changes that influence myocardial diastolic function, were examined in streptozocin (50 mg/kg)-induced diabetes mellitus (DM) in male rats. After 16 wk of regular exercise on voluntary running wheels, cardiac performance was measured in anesthetized open-chest ventilated rats. Rats with DM developed a decrease in LV end diastolic (LVED) chamber and myocardial wall compliance associated with an increase in myocardial collagen fluorescence (a measure of collagen advanced glycosylation end product concentrations), an increase in systemic blood pressure, and a dilated LV. However, LV end-systolic elastance and total myocardial hydroxyproline concentration were unchanged. Habitual exercise prevented the augmented LVED chamber stiffness (slope of linearized LVED pressure-strain relation, DM vs. exercise DM, P < 0.01) and myocardial wall stiffness (slope of linearized LVED stress-strain relation, DM vs. exercise DM, P < 0.001) produced by DM. However, neither markers of blood glucose control, blood pressure, LV geometry, myocardial hydroxyproline concentration, nor collagen fluorescence were altered by the exercise program. A reduced LVED chamber and myocardial wall stiffness, as noted in euglycemic control rats in response to regular exercise, was also not associated with hemodynamic or myocardial interstitial alterations. Therefore, regular voluntary exercise opposes the decrement in myocardial diastolic performance produced by DM in male rats without influencing the accumulation of myocardial advanced glycosylation end products thought to be partly responsible for the stiff myocardium after chronic hyperglycemia. The beneficial effects of regular exercise on myocardial compliance are likely to be a consequence of changes in active as opposed to passive properties of the myocardial wall.

Animals↗
PubMed1994

Effect of moderate dietary protein restriction on the progression of overt diabetic nephropathy: a 6-mo prospective study.

To assess whether moderate dietary protein restriction can delay the progression of overt diabetic nephropathy, 22 subjects with insulin-dependent diabetes mellitus were randomly assigned to an unrestricted protein diet (> 1.6 g.kg body wt-1.d-1) or a moderately protein-restricted diet (0.8 g.kg body wt-1.d-1) and followed prospectively for six mo. Direct isotope methods were used to assess renal function. Protein intake was assessed by measurement of urinary urea nitrogen. The two groups were well-matched for age, sex, duration of diabetes, glycemic control, blood pressure, and degree of renal insufficiency. Patients consuming the unrestricted protein diet (n = 11) showed a progressive decline in glomerular filtration rate of 1.3 mL.min-1.mo-1 with no change in proteinuria. Patients consuming the moderately protein-restricted diet showed a marked decrease in the degree of proteinuria (2.15-1.13 g/d, P = 0.036) and a stabilization of glomerular filtration rate. This occurred independently of changes in blood pressure or glycemic control. Moderate dietary protein restriction can ameliorate progression of overt diabetic nephropathy.

Adult↗
PubMed1993

The age of onset and sex distribution of insulin-dependent diabetes mellitus in Africans in South Africa.

Type I (insulin-dependent) diabetes mellitus (IDDM) appears to be rare in indigenous African populations, but little detailed information has been published. We have therefore analysed the age of onset of diabetes in 176 African patients with IDDM (age of onset < 35 years), and in 149 consecutive white patients of European extraction for comparison. In the Africans the peak age of onset occurred at 22-23 years (median 22 years) with an earlier peak from 14 to 17 years. In the Whites, the peak was found at 12-13 years (median 12 years). In only 7% of Africans did diabetes start under the age of 12 years. There was a slight female preponderance in the Africans, especially at the ages of greatest incident (20-25 years)-F:M 1.55:1. When patients with duration of diabetes less than 5 years only were analysed (the period during which early mortality among African patients was greatly reduced) the patterns of age distribution were similar to the total respective groups. A peak incidence in the winter months was noted.

Adolescent↗
PubMed1993

Voluntary total fasting in political prisoners--clinical and biochemical observations.

Thirty-three political prisoners on hunger strike (voluntary total fast--VTF) for 6-24 days were admitted to two hospitals in Johannesburg in 1989. They had been detained without trial for 4-32 months. Sound doctor-patient relationships were established by emphasis of the principle of full patient participation in clinical decision-making at every level, by rejection of police interference in patient care, and by refusal to discharge subjects back into detention. Depression and abdominal pains were the predominant symptoms. In 6 lean subjects with complete data the expected initial period of rapid weight loss was not observed. Before hospitalisation most subjects became dehydrated from inadequate fluid intake and an apparent absence of thirst. Serum creatinine concentrations were a better indication of dehydration than serum urea levels. Mild hyponatraemia was found in one-third of patients. Refeeding after 6-27 days of VTF was initiated with a dilute lactose-free formula diet, and was uncomplicated. Close clinical monitoring of subjects during VTF is essential, and it is recommended that prisoners should be admitted to hospital at 10% of weight loss, if not before. The health care of prisoners can best be provided by professionals independent of the police and prison services.

Adolescent↗
PubMed1992

Fat, protein and carbohydrate content of diets of white insulin-dependent diabetic adolescents and young adults.

Dietary habits and serum cholesterol levels were surveyed in 39 young insulin-dependent diabetic subjects (mean age (+/- SD) 17.7 +/- 4.0 years, 21 females, 18 males). All had received the routine dietary advice that total carbohydrate, fat and protein consumption should constitute more than 45-50%, less than 30-35% and less than 20% respectively of total energy intake. Of the subjects 27 (69%) consumed more fat and 21 (54%) less carbohydrate than recommended. Fat consumption correlated positively with total energy (r = 0.747; P less than 0.00001) and negatively with carbohydrate intake (r = -0.757; P less than 0.00001), suggesting that restrictions placed on carbohydrate energy sources were offset by greater fat ingestion. Serum cholesterol exceeded the recommended ideal of 5.2 mmol/l in over half the subjects, and correlated positively with body mass index. Dietary advice to insulin-dependent diabetic patients must emphasise the freer consumption of unrefined carbohydrates, so as to reduce fat intake.

Adolescent↗
PubMed1992

The relationship between the development and progression of microalbuminuria and arterial blood pressure in type 1 (insulin-dependent) diabetes mellitus.

OBJECTIVE: to investigate the association between urinary albumin excretion and arterial blood pressure in type 1 (insulin-dependent) diabetes. RESEARCH DESIGN AND METHODS: urinary albumin excretion and blood pressures were followed prospectively for a mean period of 26 months (range 18-29 months) in 46 young type 1 (insulin-dependent) diabetic subjects without overt nephropathy. Supine blood pressures (BP) were measured by a single observer using a random zero sphygmomanometer. Albumin excretion was assessed at baseline by a timed clinic excretion rate (AER; microalbuminuria = AER greater than 33 micrograms/min), and at follow-up in at least two urine specimens by the albumin/creatinine (A/Cr) ratio (micro-albuminuria = A/Cr greater than 3.7 mg/mmol). RESULTS: 39 subjects initially had normal AERs. Seven had developed microalbuminuria at follow-up: their mean BP rose from 114 +/- 13/62 +/- 13 to 119 +/- 7/77 +/- 5 mmHg (for diastolic BP, P less than 0.05), while there was no change in the mean BP in the remaining 32 patients. A rise in diastolic BP of greater than 10 mmHg occurred in five of the seven subjects who developed microalbuminuria, and in only seven of 32 who did not (P = 0.02). In the seven patients in whom microalbuminuria persisted (n = 3) or progressed to overt proteinuria (n = 4), BP increased from 123 +/- 12/70 +/- 14 to 139 +/- 12/88 +/- 10 mmHg (P less than 0.02 for both). CONCLUSIONS: this study has shown that BP is normal before the onset of microalbuminuria, and that a rise in diastolic BP accompanies the development or progression of microalbuminuria. The rate of rise in BP may be more important than the absolute level in defining 'hypertension' in young diabetic patients with microalbuminuria.

Adult↗
PubMed1992

Influence of dietary protein on glomerular filtration and urinary albumin excretion in insulin-dependent diabetes.

We investigated the effects of dietary constituents on glomerular filtration (GFR) and albumin excretion rates (AERs) in a cross-sectional study in 39 young subjects with insulin-dependent diabetes. Dietary protein intake correlated significantly in patients with GFRs less than 150 mL/min per 1.73 m2 (r = 0.53, n = 23, P = 0.009), but not with AER. GFR also correlated with mean blood glucose at a concentration less than 12.0 mmol/L (r = 0.61, P = 0.0035). Protein and fat intakes were similar in patients with and without microalbuminuria (AER greater than 20 mg/L) but long-term glycemic control was worse in the former [HbA1 12.4 +/- 2.9% (mean +/- SD) and 10.6 +/- 2.1%, respectively, P = 0.043]. In seven patients, short-term reduction of dietary protein from 2.0 to 1.0 to 0.5 g.kg-1.d-1 produced a progressive fall in GFR by 11.6 +/- 6.0 and 9.6 +/- 5.9 mL/min, respectively (P less than 0.05), but did not consistently affect AER. We conclude that both dietary protein and glycemic control influence GFR but neither alone appears to explain glomerular hyperfiltration. Microalbuminuria was associated with poor glycemic control but not with dietary fat or protein consumption.

Adolescent↗