Simple sample size calculation for cluster-randomized trials

BACKGROUND

Cluster-randomized trials, in which health interventions are allocated randomly to intact clusters or communities rather than to individual subjects, are increasingly being used to evaluate disease control strategies both in industrialized and in developing countries. Sample size computations for such trials need to take into account between-cluster variation, but field epidemiologists find it difficult to obtain simple guidance on such procedures.

METHODS

In this paper, we provide simple formulae for sample size determination for both unmatched and pair-matched trials. Outcomes considered include rates per person-year, proportions and means. For simplicity, formulae are expressed in terms of the coefficient of variation (SD/mean) of cluster rates, proportions or means. Guidance is also given on the estimation of this value, with or without the use of prior data on between-cluster variation.

CASE STUDIES

The methods are illustrated using two case studies: an unmatched trial of the impact of impregnated bednets on child mortality in Kenya, and a pair-matched trial of improved sexually-transmitted disease (STD) treatment services for HIV prevention in Tanzania.

Profit, payment and pharmaceutical practices: perspectives from hospitals in Bangkok

Means by which to improve the quality of care offered in the private sector have received increasing interest. This paper considers the influences upon hospital physician prescribing practices. It presents data on drug management practices and prescribing patterns in a sample of private for-profit, private non-profit and public hospitals in Bangkok. Clear differences emerge in prescription patterns between the different groups of hospitals: public hospitals exhibit greater use of essential drugs and generic prescribing than either group of private hospital, and prescriptions at private for-profit hospitals tended to have more essential drugs and drugs prescribed by generic name than non-profit hospitals. Prescribing patterns in public hospitals are probably largely explained by national government policy on pharmaceutical procurement. In contrast, prescribing patterns in private for-profit hospitals appear heavily influenced by pressure upon management to contain costs, in circumstances where high drug costs cannot be passed on to purchasers. Hence hospital management have developed policies encouraging the use of generic drugs and essential drugs. These same financial pressures also explain some less desirable forms of behaviour in private for-profit hospitals such as prescribing courses of antibiotic treatment of extremely short duration. Possible measures which government may take to encourage appropriate prescribing within private hospitals are discussed.

Thymic microenvironment and NZB mice: the abnormal thymic microenvironment of New Zealand mice correlates with immunopathology

There are distinct microenvironmental abnormalities of thymic architecture in several murine models of SLE defined using immunohistochemistry and a panel of mAb dissected at thymic epithelial markers. To address the issue of the relationship between the thymic microenvironment and autoimmunity, we studied backcross (NZB x NZW) F1 x NZW mice in which 50% of offspring develop nephritis associated with proteinuria and anti-DNA antibodies. We reasoned that if thymic abnormalities are associated with development of disease, the correlation of abnormalities with lupus-like disease in individual backcross mice will form the foundation for identification of the mechanisms involved. In parallel, we directed a genetic linkage analysis, using markers previously shown to be linked to nephritis and IgG autoantibody production, to determine if such loci were similarly associated with microenvironmental changes. Our data demonstrate that all (NZB x NZW) F1 x NZW backcross mice with disease have microenvironmental defects. Although the microenvironmental defects are not sufficient for development of autoimmune disease, the severity of thymic abnormalities correlates with titers of IgG autoantibodies to DNA and with proteinuria. Consistent with past studies of (NZB x NZW) F1 x NZW mice, genetic markers on proximal chromosome 17 (near MHC) and distal chromosome 4 showed trends for linkage with nephritis. Although the markers chosen only covered about 10-15% of the genome, the results demonstrated trends for linkage with thymic medullary abnormalities for loci on distal chromosome 4 and distal chromosome 1. We believe it will be important to define the biochemical nature of the molecules recognized by these mAbs to understand the relationships between thymic architecture and immunopathology.

Biodegradable positively charged ion exchange beads: a novel biomaterial for enhancing soft tissue repair

Previous work in the area of vulnerary agents is extensive. One material of focus has been positively charged ion exchange beads, which have been shown to promote a variety of wound-healing responses in several models. The goal of this work was to improve upon the clinical utility of positively charged dextran beads by creating a biodegradable version that maintains the material's inherent efficacy. A chemical method consisting of a sodium periodate oxidation was used to create a degradable diethylaminoethanol crosslinked dextran bead. The ability of this process to create a degradable bead was verified in vitro and in vivo. Furthermore, efficacy was shown in a rat linear incision model for a variety of beads exhibiting different degradation rates. The results show that efficacy is maintained by a degradable bead, but there is a diminution of the magnitude of the response as the mass loss rate is increased. Efficacy also was investigated for a moderate but completely degrading bead material over time and dose. Wound breaking strength was evaluated at days 7, 10, 14, 21, and 28 for degradable beads at doses of 10 mg/mL and 50 mg/mL. Although little difference in efficacy was noted for the increased dose, statistically significant increases over control were seen at days 7, 10, and 14 for the 10 mg/mL dose and at days 10 and 14 for the 50 mg/mL dose. At days 21 and 28 there were no differences between treated and control wounds.

Charged beads enhance cutaneous wound healing in rhesus non-human primates

Enhanced cutaneous wound healing by positively charged cross-linked diethylaminoethyl dextran beads (CLDD) was studied in a standardized incisional wound model in 20 adult and 20 geriatric Macaca mulatta (rhesus) partitioned equally over five time periods. Physiologic saline served as a control. Soft-tissue linear incisions were prepared between and 1 cm inferior to the scapulae. There were four incisions per rhesus; each incision was 1.5 cm long with 1 cm of undisturbed tissue between incisions, and both the experimental CLDD and physiologic saline treatments were administered to each rhesus. The incision treatments were either CLDD and soft-tissue closure with 4-0 BioSyn sutures or sterile physiologic saline and closure with 4-0 BioSyn sutures. The hypothesis was CLDD would enhance cutaneous wound repair. Verification of the hypothesis consisted of clinical examinations and histologic and tensiometric evaluations on biopsy specimens at 10 and 15 days, whereas 5-day and 2- and 4-month groups were assessed clinically and biopsy specimens were assessed histologically. The clinical course of healing for all groups was unremarkable. At 10 days, incisions in adult rhesus treated with CLDD had a 30-percent greater tensile strength compared with the physiologic saline-treated incisions (p = 0.01), whereas for geriatric rhesus, the CLDD treatment proved to be 15 percent greater in tensile strength compared with the physiologic saline cohort (p = 0.11). By day 15, incisions in adult rhesus were 26 percent stronger than the saline treatment group (p = 0.07), and the difference was 36 percent (p = 0.02) for the geriatric rhesus. From 5 through 15 days, histologic observations revealed a gradual decrease in quantity and integrity of CLDD, with no remnants of CLDD at either 2 or 4 months. Macrophages and multinucleated giant cells were localized in the dermis and were associated with the CLDD. These cells decreased commensurately with the decrease of CLDD beads. The data suggest that CLDD can enhance significantly the tensile properties of healing cutaneous wounds in both adult and geriatric rhesus. Moreover, if the wound healing is enhanced in geriatric patients, this finding may be clinically germane to conditions where wound healing is compromised, such as in diabetics and patients on steroids.

Assessment of an experimental bone wax polymer plus TGF-beta 1 implanted into calvarial defects

The study reported describes an experimental biodegradable polymer ceramic composite with wax-like handling properties that was combined with 2.0 micrograms of recombinant human transforming growth factor beta (rhTGF-beta(1)). The polymer/rhTGF-beta(1) combination was introduced into standard-sized calvarial defects in rabbits to evaluate biodegradability, biocompatibility, hemostasis control, and bone promotion. The experimental wound model was a standard-size circular calvarial defect 8 mm in diameter. The experimental design included 24 skeletally mature New Zealand white rabbits divided evenly between two time periods (6 and 12 weeks) and among three experimental treatments (untreated defects and defects treated with polymer with or without rhTGF-beta(1)). Evaluations consisted of clinical examinations, standarized radiography, radiomorphometry, as well as histology and histomorphometry. Data were analyzed by an Analysis of Variance (ANOVA) and Fisher's Protected Least Significant Difference test at each time period (level of significance p < or = 0.05). Radiomorphometry data indicated that standard-sized defects treated with the wax-like polymer alone and the polymer plus 2.0 micrograms of TGF-beta(1) were significantly more radiopaque than control sites at both 6 and 12 weeks. Histomorphometric data revealed the amount of new bone was significantly greater at 6 weeks in the polymer plus 2.0 micrograms of TGF-beta(1) and in the control group than in the polymer alone. Moreover, at 12 weeks, there was significantly more new bone in the control than in either the polymer alone or the polymer plus 2.0 micrograms of TGF-beta(1). We speculate the incomplete biodegradation of the polymer ceramic composite contributed to the radiopacity and may have retarded osseous regeneration. It is important that the bone wax-like polymer material was biocompatible and acted as a hemostatic agent.

Clinical case definitions for malaria: clinical malaria associated with very low parasite densities in African infants

In areas endemic for Plasmodium falciparum, clinical malaria is believed to be less common in infants than in older children, but specific case definitions have rarely been determined for this age group. As malaria case definitions are known to be both age- and site-specific, assessment of the risk of disease in infancy requires the development of appropriate diagnostic criteria. In southern Ghana, 154 children were recruited at birth and monitored for fever and malaria infection until 2 years of age. Logistic regression was used to model fever risk as a continuous function of parasite density to determine case definitions for the diagnosis of clinical malaria, and to determine age- and season-specific estimates of the fraction of fevers attributable to malaria (AF); 2360 observations were made on 154 children. For fevers defined by a measured temperature > or = 37.5 degrees C, the estimated population AF was 44% (95% confidence interval 34-53). Estimates of AF varied with age and season. For infants, AF was 51% during the wet season and 22% during the dry season; for children over one year of age, AF was 89% during the wet season and 36% during the dry season. The estimated parasite density threshold for initiation of a febrile episode was 100 parasites per microL of blood in infants, compared with 3500 parasites per microL for children over one year of age. Using these case definitions, the incidence of clinical malaria was estimated at 0.09 cases per child-year at risk for children less than 6 months of age, 0.40 for children aged 6-11 months, and 0.69 for children aged 12-23 months. Of 66 cases of clinical malaria, only 3 were observed in children under 5 months of age. We concluded that, although most fevers in infants are not due to malaria, infant clinical malaria may occur at extremely low parasite densities. This may be indicative of a lack of anti-disease immunity in this age group. In southern Ghana, an infant with axillary temperature > or = 37.5 degrees C and parasitaemia > or = 100/microL should be considered to have clinical malaria. Nevertheless, the incidence of clinical malaria is very low in children under 6 months of age, confirming that they are significantly protected from clinical malaria compared to older children.

High incidence of asymptomatic malara infections in a birth cohort of children less than one year of age in Ghana, detected by multicopy gene polymerase chain reaction

The incidence of Plasmodium falciparum infection has been followed in a birth cohort of 71 infants in southern Ghana, an area of perennial malaria transmission. Parasite DNA detection established the presence of a high rate of infection in newborns (13.6%), a low level of infection from two to 26 weeks (1.5-9.7%) and a steadily increasing parasite rate from 26 weeks of age. The median age to first infection was 42 weeks. Five cases of fever (temperature > or = 37.5 degrees C) and parasite density greater than 1,000 parasites/microl of blood, all in children more than 18 weeks of age, were considered possible cases of clinical malaria. The risk of infection was almost three times higher in the wet season than in the dry season and increased significantly from the age of 18 weeks. The level of malaria-specific IgG at birth was positively correlated with risk of infection in children 6-12 months of age, indicating that maternally derived anti-malarial IgG is correlated with exposure to malaria infection. There was no association between malaria-specific IgG at birth and risk of infection in children 0-6 months of age. However, infants do appear to possess mechanisms to limit parasite growth and a role for maternal antibody cannot be ruled out.

The potential role of peripheral health workers and community key informants in the rapid assessment of community burden of disease: the example of lymphatic filariasis

Data for planning disease control programs in most developing countries is often not available because they are usually expensive to gather. This study explored the potential use of peripheral health staff and community key informants in gathering community-level data about lymphatic filariasis. Agreement between findings of health workers and those of physicians was very high (kappa 0.66-0.87) for the clinical conditions examined. The prevalence of hydrocele was found to be a good predictor of communities at risk of filariasis. Community key informants provided very useful qualitative and quantitative data on the prevalence of clinical filariasis. The need to use nontraditional health professionals in gathering data for planing control programs is discussed.

Short-term side effects of stimulant medication are increased in preschool children with attention-deficit/hyperactivity disorder: a double-blind placebo-controlled study

Preschool children with attention-deficit/hyperactivity disorder (ADHD) (27 boys, 5 girls, mean age 4 years 10 months) participated in a double-blind placebo-controlled crossover drug study to assess the side effects of methylphenidate. Children received twice daily, for at least 1 week each, placebo, 0.3 mg/kg methylphenidate, and 0.5 mg/kg methylphenidate. Side effects were monitored by a parent rating scale designed for medication studies. In general, methylphenidate was tolerated relatively well, with no children withdrawing because of adverse effects. Of 17 childhood behaviors usually associated with side effects, 8 behaviors showed significant changes, generally at the higher dose of methylphenidate. Interestingly, 3 of the side effects were associated with improved behavior. The number of side effects appeared higher than what is usually reported in a population of school-age children, but few parents reported them as being severe. Severe side effects were reported in less than 10% of the sample, with approximately as many reports of severe effects on placebo as on low and high doses of the medication. The results indicate that methylphenidate has a relatively low toxicity in preschool children (over the first 7-10 days), that some behavioral changes that might be viewed as side effects of methylphenidate are actually normal behaviors or ADHD behaviors in preschool children (e.g., sociability), that these "side-effect" behaviors are more common in preschool than school-age children, that some "side effects" of methylphenidate are associated with improvements in behavior, and that preschool and school-age children may have different side effects of methylphenidate (e.g., mood changes and anxiety).

Ketoacidosis occurring in newly diagnosed and established diabetic children

A 6-y retrospective case note review was performed to determine the causes of ketoacidosis. 135 patients and 463 diabetic years were involved. Fifty-two ketoacidosis episodes occurred: 19 episodes in new patients and 33 episodes in 19 patients with established diabetes. 27% of newly diagnosed patients presented in ketoacidosis. They were similar in terms of age, sex and proportion living in single parent families to those presenting without ketoacidosis. The 33 ketoacidosis episodes occurring in established patients included 12 episodes in 3 children who were transferred to our care because of uncontrolled diabetes. Insulin omission was the cause of ketoacidosis in 9/19 (47%) patients, and was suspected in a further 5/19 (26%). Family and school problems were common and 14/19 patients came from single parent families. Established patients aged > or = 11 y were predominantly female (10F, 2M), whereas patients aged < or = 10 y were predominantly male (6M, 1F). 7 patients with multiple ketoacidosis episodes were all > or = 11 y and 6 were female. Families with > or = 2 diabetic children appeared vulnerable, 4 cases coming from 3/7 such families.

Clinical predictors of malaria in Gambian children with fever or a history of fever

Diagnosis of malaria in children is difficult without laboratory support because the symptoms and signs of malaria overlap with those of other febrile illnesses such as pneumonia. Nevertheless, in many parts of Africa diagnosis of malaria must be made without laboratory investigation. Therefore, a scoring system has been developed to assist peripheral health care workers in making this diagnosis. Four hundred and seven Gambian children aged 6 months to 9 years who presented to a rural clinic with fever or a recent history of fever were investigated. A diagnosis of malaria was made in 159 children who had a fever of 38 degrees C or more and malaria parasitaemia of 5000 parasites/microL or more. Symptoms and signs in children with malaria were compared with those in children with other febrile illnesses to identify features which predicted malaria. Symptoms and signs were incorporated into various logistic regression models to test which were best independent predictors of malaria and these regression models were used to construct simple scoring systems which predicted malaria. A nine terms model predicted clinical malaria with a sensitivity of 89% and a specificity of 61%, values comparable to those obtained by an experienced paediatrician without laboratory support. The ability of peripheral health care workers to diagnose malaria using this approach is now being investigated in a prospective study.

Growth factor involvement in progression of prostate cancer

Understanding how the regulation of growth factor pathways alters during prostate cancer (PC) progression may enable researchers to develop targeted therapeutic strategies for advanced disease. PC progression involves the shifting of cells from androgen-dependent growth to an androgen-independent state, sometimes with the loss or mutation of the androgen receptors in PC cells. Both autocrine and paracrine pathways are up-regulated in androgen-independent tumors and may replace androgens as primary growth stimulatory factors in cancer progression. Our discussion focuses on growth factor families that maintain homeostasis between epithelial and stromal cells in the normal prostate and that undergo changes as PC progresses, often making stromal cells redundant. These growth factors include fibroblast growth factor, insulin-like growth factors, epidermal growth factor, transforming growth factor alpha, retinoic acid, vitamin D3, and the transforming growth factor beta families. We review their role in normal prostate development and in cancer progression, using evidence from clinical specimens and models of PC cell growth.

The Gambian National Impregnated Bednet Programme: costs, consequences and net cost-effectiveness

Clinical trials have indicated that treating mosquito nets with insecticide could be a potentially cost-effective method of preventing malaria. As malaria is one of the most common causes of death in children under five in developing countries, there has been substantial interest in whether such findings can be replicated for a country's control programme in practice. The cost-effectiveness of the Gambian National Insecticide-impregnated Bednet Programme (NIBP), from the viewpoint of providers (government and non-governmental agencies) and the community, has been calculated. Information was collected from existing records, interviews with NIBP personnel, observation and household surveys. Information is provided on the resource use consequences of the NIBP in terms of reduced expenditure on anti-malaria preventive measures, treatment in government health services, household financed treatment and "charity" (burial, funeral and mourning activities), as well as cash income lost as a result of child death. The annual implementation cost of the NIBP was D757,875 (US$91,864), of which 86% was recurrent cost. The estimated number of death averted was 40.56. The net implementation cost-effectiveness ratio per death averted and discounted life years gained were D3884 (US$471) and D260 (US$31.5), respectively. Adding the cost of all mosquito nets would increase the cost-effectiveness ratios by over five times, which is an important consideration for countries with a lower coverage of mosquito nets per capita. It is concluded that insecticide-impregnated mosquito nets are one of the more efficient ways of reducing deaths in children under 10 years in rural Gambia.

An efficacy trial of the malaria vaccine SPf66 in Gambian infants--second year of follow-up

In 1994, 630 Gambian infants were immunized with three doses of the synthetic polypeptide malaria vaccine SPf66 or with a control vaccine. No significant protection against first or total attacks of malaria was observed among the children who received SPf66. However, the period of follow-up was short. Thus, 532 children were followed for a second malaria transmission season during which 291 episodes of malaria were detected. Protective efficacies of SPf66 against first attacks of malaria and against all attacks of malaria were 8% [95% CI-20%, 30%] and 2% [95% CI-26% 24%] respectively. SPf66 did not provide any significant degree of protection to Gambian infants during a second year of follow-up.

Prevalence of hydrocele as a rapid diagnostic index for lymphatic filariasis

The real burden of lymphatic filariasis in most endemic areas remains unknown even thought it is a major public health problem in many tropical countries, particularly in sub-saharan African. The nocturnal periodicity of the parasite requires parasitological examinations to be done at night. The aim of this study was to develop and validate rapid epidemiological assessment tools for the community diagnosis of lymphatic filariasis, that may be used in the future to determine the distribution of the disease and identify high risk communities in Ghana. Twenty communities with varying endemicity of filariasis were sampled from 3 endemic districts. Community members were selected for the study using a modified Expanded Programme for Immunization (EPI) cluster sampling technique. The prevalence of hydrocele was high (range 4.5-40.75%, mean = 17.78%) and the community prevalence of microfilaraemia correlated well with that of hydrocele (r = 0.84). The findings suggest that it is possible to obtain reliable and valid estimates of the community burden of lymphatic filariasis using the prevalence of hydrocele as a diagnostic index.

Skill acquisition in sport: some applications of an evolving practice ecology

This paper builds on recent theoretical concerns regarding traditional conceptualizations of the skill acquisition process. The implications for the process of practice in sport contexts are explored with reference to the information-processing approach to motor behaviour and the newer ecological paradigm. Issues are raised with current principles of practice based on traditional theoretical ideas. A practice strategy that gives greater weight to the guided exploration of the practice workspace jointly defined by the properties of the individual's subsystems, the specific task and the environment is advocated. Such a constraints-led perspective supersedes previous distinctions between rudimentary and voluntary skills. Sports scientists, coaches, teachers and movement rehabilitation therapists are invited to review current practices in the light of recent theoretical advances from the ecological perspective.

Plasmodium vivax: a cause of malnutrition in young children

We studied the aetiology of malnutrition in a cohort of 1511 children < 10 years old in Espiritu Santo, Vanuatu. Malnutrition was categorized using standard anthropometric criteria as: underweight [weight-for-age (WA) Z score < -2], wasting [weight-for-height (WH) Z < -2], or stunting [height-for-age (HA) Z < -2]. On multiple logistic regression analysis, the only factors significantly associated with wasting were age < 5 years [OR (95% CI) 1.8 (1.2-2.9), p = 0.01] and having suffered one or more episodes of clinical P. vivax malaria in the 6 months preceding nutritional assessment [OR 2.4 (1.3-4.4), p = 0.006]. The incidence of P. vivax infection was significantly higher during the 6 months preceding assessment in underweight vs. non-underweight children [incidence rate ratio (IRR) 2.6 (1.5-4.4), p < or = 0.0001). These groups had similar incidences of clinical P. falciparum infection during the same period [IRR 1.1 (0.57-2.1) p = 0.8] and of either species during the 6 months following assessment [IRR P. vivax 1.3 (0.9-2.0) p = 0.2; IRR P. falciparum 1.3 (0.9-1.9) p = 0.2]. In these children, P. vivax malaria was a major predictor of acute malnutrition; P. falciparum was not. Wasting neither predisposed to nor protected against malaria of either species. Although P. vivax malaria is generally regarded as benign, it may produce considerable global mortality through malnutrition.

Follow-up of Gambian children recruited to a pilot safety and immunogenicity study of the malaria vaccine SPf66

A pilot safety and immunogenicity trial of the malaria vaccine SPf66 was undertaken in The Gambia in 1993. One hundred and fifty infants aged 6-11 months were immunized with either 0.5 mg or 1.0 mg of SPf66 produced either in Colombia or in the USA or with a control vaccine. Children who received SPf66 experienced more clinical attacks of malaria than did children in the control group during the first period of surveillance and the difference in incidence between children who had received high dose Colombian vaccine and the control children was statistically significant at the 5% level. During the 1995 malaria transmission season, 127 children from the original cohort of 150 were observed. During 18 weeks of intensive surveillance, the incidence of clinical malaria was again higher among children who had received SPf66 than among children who had received inactivated polio vaccine (6.23 vs 4.89 clinical attacks per 1000 days at risk), the effect being most marked among children who were in the high dose groups, but differences between groups were now no longer statistically significant.

The Gambian National Impregnated Bed Net Programme: evaluation of effectiveness by means of case-control studies

Two case-control studies, one on mortality and the other on malaria morbidity, were carried out in order to evaluate the impact of the Gambian National Insecticide Bed Net Programme during the second year of intervention and to explore the feasibility of such a study for the evaluation of programme effectiveness. For the mortality study, children 1-9 years old who died during the 1993 rainy season were matched by age and sex with 2 healthy controls from the same village. For the morbidity study, children 1-9 years old attending Fatoto or Jahalia Health Centres in The Gambia and who had fever and parasitaemia > or = 5000/microL were matched by age with a child attending the health centres without fever or parasitaemia. An additional healthy control was recruited from the case's village. No impact of insecticide-treated bed nets on mortality was detected and this was in keeping with the results obtained by prospective surveillance. A protective effect of insecticide-treated nets on malaria morbidity was detected when cases were compared with controls recruited at the health centres. However, this disappeared when cases were compared with controls recruited from the cases' villages. The mortality case-control study suggested that reducing the time between onset of disease and treatment may have an important impact on childhood mortality. In order to calculate programme cost-effectiveness, important for informed resource allocations to be made by health managers, it is essential to obtain evidence of effectiveness. This can be done by means of case-control studies, which are easier to carry out and require fewer resources than prospective surveillance. Nevertheless, it is necessary to be conscious of their pitfalls, particularly of the bias involved in the choice of cases and controls. The measurement of insecticide on the nets of the cases or controls is essential for such studies.

Effects of methylphenidate on preschool children with ADHD: cognitive and behavioral functions

OBJECTIVE

To report on implications for methylphenidate treatment of this very young age group and the need to examine factors related to achieving compliance.

METHOD

Thirty-one children with attention-deficit hyperactivity disorder (ADHD), aged 4 to 6 years, participated in a double-blind, placebo-controlled study using placebo, 0.3 mg/kg, and 0.5 mg/kg of methylphenidate twice per day.

RESULTS

Improvements related to medication were obtained on cognitive tests of attention and impulsivity as well as behaviors assessed by parent rating scales. In an interactive setting with their mothers, attentional abilities and the children's ability to work more productively also showed improvement. However, no changes were obtained with respect to the children's tendency to comply with parental requests. Side effects increased slightly with the high dosage of medication but remained mild.

CONCLUSION

The results suggest that methylphenidate can be used to improve the functioning of preschool-age children with ADHD, in a manner similar to their school-age counterparts.