Survey and surveillance development in settings with low human immunodeficiency virus prevalence.

In most countries, during the early phases of a human immunodeficiency virus epidemic, independently initiated surveys of perceived high-risk groups tend to precede the development of formal surveillance systems. Unfortunately, in low-prevalence settings, small sample sizes produce unreliable estimates of prevalence and trends, with an inevitable tendency towards positive results. In our study, we present sample size calculations and typical samples used in actual surveys, with Pakistan as our example. More useful data on risk behaviour and potential for spread can be derived from the study of commoner sexually transmitted diseases and associated risk behaviours, including assessments of knowledge, attitudes, beliefs and practices.

Hepatitis B and C infection in first-time blood donors in Karachi--a possible subgroup for sentinel surveillance.

Hepatitis B virus (HBV) and C virus (HCV) are major public health concerns in Pakistan. We conducted a baseline analysis of first-time replacement blood donors at the blood bank of Jinnah Postgraduate Medical Centre in the year 2000 with the view to developing low-cost sentinel surveillance for these infections. Among 7325 such donors, 264 (3.6%) were positive for anti-HCV and 344 (4.7%) for HBsAg. HCV seroprevalence was significantly positively associated with age and lower education. Those speaking Sindhi or other minor languages had a significantly higher prevalence of HBV infection. Blood bank data could provide reliable information to monitor trends in prevalence of these infections.

Hepatitis B and C infection in first- time blood donors in Karachi - a possible subgroup for sentinel surveillance

Hepatitis B virus [HBV] and C virus [HCV] are major public health concerns in Pakistan. We conducted a baseline analysis of first- time replacement blood donors at the blood bank of Jinnah Postgraduate Medical Centre in the year 2000 with the view to developing low- cost sentinel surveillance for these infections. Among 7325 such donors, 264 [3.6%] were positive for anti- HCV and 344 [4.7%] for HBsAg. HCV seroprevalence was significantly positively associated with age and lower education. Those speaking Sindhi or other minor languages had a significantly higher prevalence of HBV infection. Blood bank data could provide reliable information to monitor trends in prevalence of these infections

Clinical decision making Part I: errors of commission and omission.

Clinical decision making refers to any act of diagnosis that leads to a decision regarding prognosis, treatment, referral or counseling. It has long been recognized that diagnostic probabilities influence perceptions and judgements in medical practice. However, so do ethical values affect clinical judgements, even if these lead to adverse consequences: for example, to judge a well person sick is considered "more ethical" than to judge a sick person well. This dilemma confronts us also when having to choose between what are called Type 1 and Type 2 errors, and the consequences of either may be serious. Other factors that should be taken into account, as they can affect the "pretest likelihood" or "prior probability" of disease and the error rates obtained, include the individual circumstances of the patient (e.g. socioeconomic background), the organizational setting (e.g. patient volume, cultural practices and norms), and system differences (e.g. fee for service versus salaried service). In Part II of this two-part series,we explore in greater depth the mathematical basis for why various diagnostic procedures perform differently in different settings.

Evaluation of a water, sanitation, and hygiene education intervention on diarrhoea in northern Pakistan.

OBJECTIVE: Inadequate water and sanitation services adversely affect the health and socioeconomic development of communities. The Water and Sanitation Extension Programme (WASEP) project, undertaken in selected villages in northern Pakistan between 1997 and 2001, was designed to deliver an integrated package of activities to improve potable water supply at village and household levels, sanitation facilities and their use, and awareness and practices about hygiene behaviour. METHODS: A case-control study was conducted during July-September 2001 to evaluate whether, after selected confounders were controlled for, children aged <6 years with diarrhoea were more or less likely to reside in villages that participated in the project than in villages that did not participate. Descriptive and logistic regression analyses were performed. FINDINGS: Children not living in WASEP villages had a 33% higher adjusted odds ratio for having diarrhoea than children living in WASEP villages (adjusted odds ratio, 1.331; P<0.049). Boys had 25% lower odds of having diarrhoea than girls (adjusted odds ratio, 0.748; P<0.049). A 2.6% decrease was found in the odds of diarrhoea for every yearly increase in the mother's age (adjusted odds ratio, 0.974; P<0.044) and a 1.4% decrease for every monthly increase in the child's age (adjusted odds ratio, 0.986; P<0.001). CONCLUSIONS: The findings in this study may help refine the approach to future water, sanitation, and hygiene initiatives in northern Pakistan. The integrated approach taken by WASEP, which incorporates engineering solutions with appropriate education to maximize facility usage and improve hygiene practices, is a useful example of how desired health benefits can be obtained from projects of this type.

The obesity pandemic--implications for Pakistan.

BACKGROUND: Adverse health outcomes are associated with overweight and obesity. In February 2000, the WHO Regional Office for the Western Pacific, the International Association for the Study of Obesity and the International Obesity Task Force published provisional recommendations for adults for the Asia-Pacific region: overweight at Body Mass Index (BMI) > or = 23 and obesity at BMI > or = 25. METHODS: Data from the National Health Survey of Pakistan, 1990-94 were reanalyzed using BMI cut-offs recommended for Asians to reassess prevalence of overweight and obesity in the adult Pakistani population. RESULTS: Prevalence of obesity (BMI > or = 25) in 25-44 year olds in rural areas was 9% for men and 14% for women; in urban areas, prevalence was 22% and 37% for men and women, respectively. For 45-64 year olds, prevalence was 11% for men and 19% for women in rural areas, and 23% and 40% in urban areas for men and women, respectively. Obesity prevalence was directly associated with SES, regardless of residence. CONCLUSION: In South Asia, including Pakistan, social and environmental changes are occurring rapidly, with increasing urbanization, changing lifestyles, higher energy density of diets, and reduced physical activity. The coexistence of underweight in early life with obesity in adults may presage both a higher prevalence and incidence for noncommunicable diseases (NCDs) such as hypertension and diabetes. Use of BMI > or = 23 for overweight, and BMI > or = 25 for obesity, may provide a more accurate determination of the health of Pakistanis, especially in those with more than one risk factor for NCDs.

Survey and surveillance development in settings with low human immunodeficiency virus prevalence.

In most countries, during the early phases of a human immunodeficiency virus epidemic, independently initiated surveys of perceived high-risk groups tend to precede the development of formal surveillance systems. Unfortunately, in low-prevalence settings, small sample sizes produce unreliable estimates of prevalence and trends, with an inevitable tendency towards positive results. In our study, we present sample size calculations and typical samples used in actual surveys, with Pakistan as our example. More useful data on risk behaviour and potential for spread can be derived from the study of commoner sexually transmitted diseases and associated risk behaviours, including assessments of knowledge, attitudes, beliefs and practices.

Survey and surveillance development in settings with low human immunodeficiency virus prevalence

In most countries, during the early phases of a human immunodeficiency virus epidemic, independently initiated surveys of perceived high-risk groups tend to precede the development of formal surveillance systems. Unfortunately, in low-prevalence settings, small sample sizes produce unreliable estimates of prevalence and trends, with an inevitable tendency towards positive results. In our study, we present sample size calculations and typical samples used in actual surveys, with Pakistan as our example. More useful data on risk behaviour and potential for spread can be derived from the study of commoner sexually transmitted diseases and associated risk behaviours, including assessments of knowledge, attitudes, beliefs and practices

Antibiotic prophylaxis post-tonsillectomy: is it of benefit?

The decision to prescribe antibiotics post-tonsillectomy still remains controversial. However, recent changing trends in the tonsillar tissue microflora have been widely reported, with Haemophilus influenzae, Staphylococcus aureus and anaerobic organisms all being implicated. All of the above are beta-lactamase producers and thus render lactamase prone antibiotics inactive. We compared two groups of children, one on Amoxycillin and clavulanic acid (a lactamase stable antibiotic with anaerobic cover) for 1 week post tonsillectomy--Group A (N = 44), and another group on no treatment--Group B (N = 34). We compared tonsillar core, surface and postoperative tonsillar fossae bacteriological profiles in the two groups. The tonsil core pathogens included H. influenzae (64%) of which 9.5% were beta-lactamase producers, Streptococcus viridans (55.9%), S. aureus (37%) of which 86% were beta-lactamase producers, and anaerobes which were found in 25% of samples. We found that there was considerably less morbidity in those children receiving postoperative antibiotics compared to those who did not, as judged by the amount of analgesia consumed (p = 0.379), time to resumption of normal diet (p = 0.0072) and pain analogue scores (p = 0.0006). We feel that treating children who have undergone tonsillectomy with amoxycillin and clavulanic acid significantly reduces postoperative morbidity.

Vitreoretinal findings similar to retinopathy of prematurity in infants with compound heterozygous protein S deficiency.

OBJECTIVE: To present previously undescribed vitreoretinal findings similar to severe retinopathy of prematurity (ROP) in two siblings (daughter and son) with a thrombophilic disorder, compound heterozygous protein S (PS) deficiency. DESIGN: Family genotype study and literature review. PARTICIPANTS: Two unrelated heterozygous PS-deficient parents and their two children with compound heterozygous PS deficiency were studied. The gestational age and birth weight of the daughter were 40 weeks and 3200 g, respectively, and those of the son were 34 weeks and 2150 g, respectively. Three other neonates with homozygous or compound heterozygous PS deficiency and ophthalmologic findings were identified in the literature. INTERVENTION: The daughter underwent lensectomy-vitrectomy at 48 weeks adjusted age bilaterally. The son underwent therapy developed for severe ROP: laser therapy of the peripheral avascular retina at 39 weeks adjusted age, and bilateral lensectomy-vitrectomy with membrane peel of intravitreous proliferation from the optic disc at 42 weeks adjusted age. MAIN OUTCOME MEASURES: The main clinical outcome measures were retinal appearance and functional vision. Genotypes of the family members were determined. RESULTS: One of the four eyes retained functional vision. A normal-appearing posterior retina, normal scotopic and photopic flash electroretinograms, and a normal flash visual-evoked response were documented from the left eye of the son at 62 weeks adjusted age. The other three eyes had inoperable retinal detachments and no functional vision. The mother had type I PS deficiency and the father had type II PS deficiency. Compound heterozygous PS deficiency was confirmed in both children. CONCLUSION: In both children, normal vasculogenesis was interrupted. At 39 weeks adjusted age, the retinal examination of the son revealed extraretinal fibrovascular proliferation at the optic disc (reactivation of the hyaloid system) and in the peripheral retina (interruption of inner retinal vascularization). Patients with homozygous or compound heterozygous PS deficiency may present as infants with severe ROP. The authors' experience suggests that appropriately timed surgical procedures, which are efficacious for ROP, can preserve vision in infants with thrombophilic disorders.

A small foveal avascular zone may be an historic mark of prematurity.

OBJECTIVE: To compare in children the area and diameter of the foveal avascular zone (FAZ) of former preterm infants, when no significant retinopathy of prematurity (ROP) developed, to the area and diameter of the FAZ of former term infants. DESIGN: Retrospective observational case series and literature review. PARTICIPANTS: Forty-nine children (39 former preterm infants and 10 former term infants) between the ages of 1 and 17 years had fluorescein angiograms. All of these children had been appropriate weight for gestational age at birth and had no genetic disorders. Neither eye of any of these children had any macular ectopia or vessel traction, had been treated for active ROP, had developed active ROP >stage 3 mild, or had any refractive error > +/- five diopters. Every child had a visual acuity of 20/40 or better in both eyes. METHODS: The area and greatest diameter of the FAZ were measured using digital image analysis of masked fundus fluorescein angiograms. Variables of gender, race, multiple birth, gestational age, birth weight, ROP stage, age, and refraction at the time of fluorescein angiography, and final visual acuity were recorded. RESULTS: Increasing FAZ area and greatest diameter correlated significantly with increasing gestational age and birth weight: FAZ area (microm2) versus gestational age (weeks) (R/F/P = 0.88/166.70/<0.0001); FAZ greatest diameter (microm) versus gestational age (weeks) (R/F/P = 0.87/151.10/<0.0001); FAZ area (micro/m2) versus birth weight (g) (R/F/P = 0.88/167.06/<0.0001); and FAZ greatest diameter (microm) versus birth weight (g) (R/F/P = 0.87/148.74/ <0.0001). A small or absent FAZ was found in all former preterm infants who had been < or = 30 weeks gestational age or had weighed < or = 1100 g at birth. A normal FAZ was present in all children who had been > or = 36 weeks gestational age or had weighed > or = 2650 g at birth. None of the other parameters studied correlated with FAZ area or greatest diameter. CONCLUSION: This study provides evidence that the FAZ in developing humans is initially densely vascularized with a fine meshwork of inner retinal vessels during vasculogenesis. This vascular meshwork undergoes regression by apoptosis in all infants > or = 36 weeks gestational age at birth to form a normal FAZ, but apoptosis almost never occurs in preterm infants < or = 30 weeks gestational age at birth. Although there is no effect on final visual acuity, a small or absent FAZ may be an historic mark of prematurity.

Intraocular lenses in children: changes in axial length, corneal curvature, and refraction.

AIM: To assess changes in axial length, corneal curvature, and refraction in paediatric pseudophakia. METHODS: 35 eyes of 24 patients with congenital or developmental lens opacities underwent extracapsular cataract extraction and posterior chamber intraocular lens implantation. Serial measurements were made of axial length, corneal curvature, objective refraction, and visual acuity. RESULTS: For patients with congenital cataracts (onset < 1 year age) the mean age at surgery was 24 weeks. Over the mean follow up period of 2.7 years, the mean increase in axial length of 3.41 mm was not significantly different from the value of an expected mean growth of 3.44 mm (paired t test, p = 0.97) after correction for gestational age. In the developmental cataract group (onset > 1 year of age) the mean age at surgery was 6.4 years with a mean follow up of 2.86 years. This group showed a mean growth in axial length of 0.36 mm that was not significantly different from an expected value of 0.47 mm (paired t test, p = 0.63). The mean preoperative keratometry was 47.78 D in the congenital group and 44.35 D in the developmental group. At final follow up the mean keratometry in the congenital group was 46.15 D and in the developmental group it was 43.63 D. In eyes followed for at least 2 years, there was an observed myopic shift by 24 months postoperatively of 3.26 D in the congenital cases (n = 10) and 0.96 D in the developmental cases (n = 18). CONCLUSION: The pattern of axial elongation and corneal flattening was similar in the congenital and developmental groups to that observed in normal eyes. No significant retardation or acceleration of axial growth was found in the eyes implanted with IOLs compared with normal eyes. A myopic shift was seen particularly in eyes operated on at 4-8 weeks of age and it is recommended that these eyes are made 6 D hypermetropic initially with the residual refractive error being corrected with spectacles.

Status of national diabetes programmes in the Americas.

Reported are the responses in the latter half of 1997 of all ministries of health in the Region of the Americas to the Declaration of the Americas on Diabetes, which was adopted by the Directing Council of the Pan American Health Organization (PAHO) in 1996 as a basis for national programme development in diabetes. The short-term targets were the designation of national focal points, the preparation of national estimates of the disease burden, and the development and implementation of national strategies and plans to deal with diabetes. The survey found that most countries recognized diabetes as a significant public health problem. In terms of global relevance, a number of lessons have been learned from this exercise: the role of broadly based participation in gaining recognition at the national health policy level; the wide acceptance of an integrated programme model; the relevance of process-related targets to achieve short-term success; and the critical role of having a designated focal point within the managerial approach.

Capture-recapture: reconnaissance of a demographic technique in epidemiology.

The objective of this paper is to review capture-recapture (CR) methodology and its usefulness in epidemiology. Capture-recapture is an established and well-accepted sampling tool in wildlife studies, and it has been proposed as a cost-effective demographic technique for conducting censuses. However, the application of CR in the field of epidemiology requires consideration of relevant factors such as the nature of the condition under surveillance, its case definition, patient characteristics, reporting source and propensity for misdiagnosis and underdiagnosis. The use of CR in epidemiology has expanded over the last 10 years and no doubt will continue to be adopted. Although it has a role in public health surveillance, a more traditional approach to disease monitoring seems more advantageous in certain instances.

Refractive outcome in eyes with retinopathy of prematurity treated with cryotherapy or diode laser: 3 year follow up.

AIMS: To compare the refractive error 1 to 3 years after cryotherapy or diode laser treatment for threshold retinopathy of prematurity. METHODS: Twenty six infants treated with diode laser and 17 infants treated with cryotherapy underwent cycloplegic refraction during follow up. RESULTS: After 3 years of follow up, 94.1% of patients had myopia (right eye if bilateral) following cryotherapy and 45.5% of patients had myopia following diode laser treatment. The difference between the two proportions was 48.7% (95% confidence interval 17.8 to 80.1, p = 0.004). In the cryotherapy group 55% of patients were highly myopic (> -6.00 dioptres) while in the laser group there were no high myopes. CONCLUSIONS: In the diode laser group there were significantly fewer myopes than in the cryotherapy group up to 3 years after the procedure. There was no trend towards increasing myopia in the laser treated group and the refraction in these eyes stabilised after 1 year. In the cryotherapy group there was a significant increase in the degree of myopia between year 1 and year 3 of follow up (p = 0.02). Diode laser treatment is thought to be as effective as cryotherapy, and has the added benefit of reducing myopia, in the treatment of ROP.