A semiparametric empirical likelihood method for data from an outcome-dependent sampling scheme with a continuous outcome

Outcome-dependent sampling (ODS) schemes can be a cost effective way to enhance study efficiency. The case-control design has been widely used in epidemiologic studies. However, when the outcome is measured on a continuous scale, dichotomizing the outcome could lead to a loss of efficiency. Recent epidemiologic studies have used ODS sampling schemes where, in addition to an overall random sample, there are also a number of supplemental samples that are collected based on a continuous outcome variable. We consider a semiparametric empirical likelihood inference procedure in which the underlying distribution of covariates is treated as a nuisance parameter and is left unspecified. The proposed estimator has asymptotic normality properties. The likelihood ratio statistic using the semiparametric empirical likelihood function has Wilks-type properties in that, under the null, it follows a chi-square distribution asymptotically and is independent of the nuisance parameters. Our simulation results indicate that, for data obtained using an ODS design, the semiparametric empirical likelihood estimator is more efficient than conditional likelihood and probability weighted pseudolikelihood estimators and that ODS designs (along with the proposed estimator) can produce more efficient estimates than simple random sample designs of the same size. We apply the proposed method to analyze a data set from the Collaborative Perinatal Project (CPP), an ongoing environmental epidemiologic study, to assess the relationship between maternal polychlorinated biphenyl (PCB) level and children's IQ test performance.

Salicylates inhibit flavivirus replication independently of blocking nuclear factor kappa B activation

Flaviviruses comprise a positive-sense RNA genome that replicates exclusively in the cytoplasm of infected cells. Whether flaviviruses require an activated nuclear factor(s) to complete their life cycle and trigger apoptosis in infected cells remains elusive. Flavivirus infections quickly activate nuclear factor kappa B (NF-kappaB), and salicylates have been shown to inhibit NF-kappaB activation. In this study, we investigated whether salicylates suppress flavivirus replication and virus-induced apoptosis in cultured cells. In a dose-dependent inhibition, we found salicylates within a range of 1 to 5 mM not only restricted flavivirus replication but also abrogated flavivirus-triggered apoptosis. However, flavivirus replication was not affected by a specific NF-kappaB peptide inhibitor, SN50, and a proteosome inhibitor, lactacystin. Flaviviruses also replicated and triggered apoptosis in cells stably expressing IkappaBalpha-DeltaN, a dominant-negative mutant that antagonizes NF-kappaB activation, as readily as in wild-type BHK-21 cells, suggesting that NF-kappaB activation is not essential for either flavivirus replication or flavivirus-induced apoptosis. Salicylates still diminished flavivirus replication and blocked apoptosis in the same IkappaBalpha-DeltaN cells. This inhibition of flaviviruses by salicylates could be partially reversed by a specific p38 mitogen-activated protein (MAP) kinase inhibitor, SB203580. Together, these results show that the mechanism by which salicylates suppress flavivirus infection may involve p38 MAP kinase activity but is independent of blocking the NF-kappaB pathway.

Semiparametric analysis of truncated data

Randomly truncated data are frequently encountered in many studies where truncation arises as a result of the sampling design. In the literature, nonparametric and semiparametric methods have been proposed to estimate parameters in one-sample models. This paper considers a semiparametric model and develops an efficient method for the estimation of unknown parameters. The model assumes that K populations have a common probability distribution but the populations are observed subject to different truncation mechanisms. Semiparametric likelihood estimation is studied and the corresponding inferences are derived for both parametric and nonparametric components in the model. The method can also be applied to two-sample problems to test the difference of lifetime distributions. Simulation results and a real data analysis are presented to illustrate the methods.

Ethnic issues in the epidemiology of childhood obesity

Childhood obesity may be seen as a marker for high-risk dietary and physical inactivity practices. Recent increases in the prevalence of overweight and obesity among American children are not limited to one age, gender, or ethnic group, which suggests that unique behaviors of the members of various racial or ethnic subgroups of the population are unlikely to be the major contributing factors. Rather, it seems that environmental changes promoting increased energy intake and decreased energy output are occurring and have widespread impact on children from various backgrounds. Although no ethnic group is immune from the current shift in energy balance, differential rates of overweight seem to exist among ethnic groups. National probability samples of African-American, Hispanic, and white children in the United States provide clear evidence that white children are at lower risk for childhood overweight than are African-American or Hispanic children. Of concern is the lack of national data on the prevalence of overweight and obesity for Native-American and Asian-American groups. Also of concern is the aggregation of racial and ethnic subgroups, which may render prevalence rates meaningless. This possibility is clearly true with some surveys of weight status that combine diverse populations, such as Asians and Pacific Islanders, into one group. The high rates of obesity in African-American, Hispanic, and Native-American children are of concern. Although parental SES is associated inversely with childhood obesity among whites, higher SES does not seem to protect African-American and Hispanic children against obesity. In these groups, childhood obesity does not seem to be associated significantly with parental income and education. Health consequences of childhood obesity include a higher prevalence of type 2 diabetes and an increased risk for adverse levels of lipids, lipoproteins, and blood pressure. The effects of recently reported unprecedented levels of childhood overweight on subsequent risk for obesity in middle age are not known until future longitudinal data can be collected. It seems likely, however, that future health consequences of current early and severe childhood obesity will be staggering. Funding for adult follow-up of longitudinal studies of high-risk African American, Hispanic, and Native-American children is needed urgently to provide information on the long-term effects of childhood obesity. Halting the obesity epidemic is a formidable task, but the success in recent decades of drastically reducing childhood undernutrition offers hope and should spur similar action and leadership efforts. Promotion of efforts to reduce excess caloric intake with efforts to increase energy expenditure should receive paramount attention in the design of health programs. Given the relatively few published obesity-prevention and treatment studies that are designed to address specific cultural issues, it is important to promote the development of culturally appropriate intervention strategies that are shown to be effective among youth of diverse backgrounds. Although the dietary and activity goals will be similar, parental, family, and community messages and techniques grounded in cultural traditions and norms will be different for each ethnic group. This approach is crucial in the United States, a country with an increasingly diverse population.

Incidence, transmission, and clinical significance of hepatitis G virus infection in hemodialysis patients

A high prevalence of hepatitis G virus (HGV) infection has been noted in patients receiving chronic hemodialysis (HD) therapy, yet the incidence rate and transmission route have rarely been reported. Serum samples from 160 chronically uremic patients in a HD unit were initially collected at the time chronic HD therapy was begun, and thereafter annually in July and, finally, in November 1999. Serum HGV RNA was detected using nested reverse transcription polymerase chain reaction, and HGV E2 antibody was determined using an enzyme immunoassay. Nucleotide sequences of the 5'-noncoding region were studied in the HD patients with HGV viremia. Forty healthy staff members were also enrolled as control subjects. Three of the 40 (7.5%) healthy staff members were positive for HGV RNA or HGV E2 antibodies, in contrast to 40 of the 160 (25%) HD patients, including 14 (8.8%) who were positive for HGV RNA only, 25 (15.6%) who were positive for HGV E2 antibody only, and 1 (0.6%) who had both markers. HGV exposure did not correlate with gender, age, duration of HD therapy, or history of blood transfusions. At least 20 of the 40 (50%) patients with HGV exposure had been infected before the start of chronic HD therapy. Nevertheless, at least nine (22.5%) patients acquired new HGV infections after starting chronic HD therapy, with an incidence rate of > or = 2.6% per year. Three patients with newly acquired HGV viremia after HD therapy was started and two with pre-existing HGV viremia before HD therapy was started had the same nucleotide sequences. HGV and HCV infections (with a prevalence of 14.4%) might have been transmitted independently in HD patients. In addition, HGV infection was not found to cause significant elevation of alanine aminotransferase levels in the group exposed to HGV. To conclude, the incidence of new HGV infections was at least 2.6% per year. In addition to transmission through blood transfusion, HGV may have been transmitted nosocomially patient-to-patient within the HD unit. The compliance with standard universal precautions should be carefully re-examined, but it is not necessary to routinely screen for HGV infection among patients on chronic HD.

Generalized argyria in two chronic hemodialysis patients

Silver can be absorbed through ingestion, topical administration, or inhalation. Generalized argyria results from deposition of silver in the skin, nails, mucous membranes, and internal organs and is characterized by a diffuse bluish-gray discoloration in sun-exposed areas. We report two cases of generalized argyria in patients on maintenance hemodialysis (HD) therapy for more than 15 years. They presented with diffuse hyperpigmentation of the face that was mistaken to be related to uremia and bluish-gray discoloration of all nails believed to be cyanosis. Histopathologic examination of skin biopsy specimens showed characteristic findings of argyria, which was further confirmed by radiograph microanalysis. Their serum silver levels were also elevated. No definite silver source could be determined. However, their argyria might be related to their long-term HD therapy because (1) they had been on HD therapy for more than 15 years and the discoloration appeared several years afterward, and (2) the water used for HD was not well processed in the early 1980s in TAIWAN: Argyria should be suspected in chronic HD patients presenting with a diffuse bluish-gray discoloration of the skin and nails and evaluated carefully by skin biopsy.

Efficacy of a mass hepatitis B immunization program after switching to recombinant hepatitis B vaccine: a population-based study in Taiwan

To study the efficacy of immunization against hepatitis B after plasma-derived vaccine was replaced by recombinant vaccine, 2-year-old Taiwanese children were recruited by stratification random sampling and tested for hepatitis B markers. They were grouped according to maternal infectivity and children's immunization status. Of 2010 children, 2.5% had hepatitis B surface antigen (HBsAg), 94.1% had its antibody (anti-HBs), 6.8% had core antibody, and 3.3% were seronegative. Children of highly infectious mothers immunized with hepatitis B immunoglobulin and vaccine on schedule had a lower HBsAg-positive rate and a higher anti-HBs-positive rate than those with vaccine only and off-schedule. The efficacy of the Taiwanese mass hepatitis B immunization was maintained after switching to recombinant hepatitis B vaccine.

Extreme metabolic alkalosis treated with normal bicarbonate hemodialysis

Metabolic alkalosis (MA), defined as a primary increment in plasma bicarbonate concentration, is a common complication in hospitalized patients and is associated with high morbidity and mortality in severe cases. One of the major routes of compensation for MA (ie, the secretion of an alkaline urine) is lost in renal failure patients. We report three cases involving four episodes of extreme MA with an arterial pH value greater than 7.60, serum bicarbonate concentration greater than 55 mmol/L, and stupor or seizure. Profound vomiting or massive gastric drainage combined with concurrent oliguric renal failure was the underlying mechanism for severe MA. Hydration and normal central venous pressure failed to improve the MA. The extreme MA was reversed quickly and safely by conventional hemodialysis with normal bicarbonate dialysate of 25 to 28 mmol/L. To our knowledge, this is the first reported successful use of normal bicarbonate dialysate in the treatment of severe MA. We also found that either H(2) blockers or proton-pump inhibitors have a prophylactic effect on the formation of MA.

Change in the area of laser posterior capsulotomy: 3 month follow-up

PURPOSE

To monitor the change in the area of laser posterior capsulotomy over time to determine whether and when the area becomes stable.

SETTING

Taipei Municipal Yang-Ming Hospital, Taipei, Taiwan, Republic of China.

METHODS

This prospective study comprised 53 eyes (46 patients) with posterior capsule opacification (PCO) that had neodymium:YAG (Nd:YAG) laser posterior capsulotomy. The capsulotomy area was measured 30 minutes, 1 week, and 1 and 3 months postoperatively. The correlations between the capsulotomy area and changes in other measurements were also evaluated.

RESULTS

The capsulotomy area increased significantly 1 month after laser treatment and stabilized thereafter. The mean area increased from 9.26 mm(2) +/- 0.47 (SEM) to 10.88 +/- 0.66 mm(2) (17.49%) after 3 months. At 3 months, the area was 19.10% +/- 4.85% larger than at 30 minutes after capsulotomy. The change in area did not correlate significantly with changes in intraocular pressure, anterior chamber depth, spherical equivalent, refractive astigmatism, keratometric astigmatism, or residual astigmatism from 1 week after treatment.

CONCLUSION

The capsulotomies enlarged progressively up to 1 month after Nd:YAG laser posterior capsulotomy for PCO and stabilized thereafter.

Adult-onset minimal change disease among Taiwanese: clinical features, therapeutic response, and prognosis

There are some racial differences in the prevalence and prognosis of idiopathic nephrotic syndrome; however, reports about minimal change disease (MCD) in Chinese were rare. We retrospectively analyzed 123 Chinese adults with idiopathic nephrotic syndrome, who received percutaneous renal biopsy in our institution within the last 10 years. In total, 46 patients (37.4%) were compatible with the pathological diagnosis of MCD. The male to female ratio was 1.2:1. The mean age of onset was 30.9 years, and 80% of the patients with MCD were less than 40 years. The mean daily proteinuria was 10.2 g, and serum albumin was 1.8 mg/dl. Azotemia occurred in 16 (35%) of 46 cases; hypertension, 13%; and microscopic hematuria, 13%. High selectivity index for proteinuria (SI <0.1) was noted in 12 (39%) of 31 cases; and high IgE level was found in 83.7% of the study subjects, although only one case had allergic history. Complete remission in 36 MCD patients treated with corticosteroid was achieved by 42% (15/36), 80% (29/36), and 94% (34/36) within 4, 8, and 12 weeks, respectively. The time interval to remission was similar between the younger group (<40 years old, 1.7 months) and older group (>40 years old, 1.6 months). Nineteen (56%) of 34 cases with steroid response did not relapse, and the other cases (44%) had a mean relapse rate of 1.5 times per patient within a period of 45 months. The age of onset in MCD cases was not significantly correlated with steroid-responsive rate, and the time interval to remission. However, a tendency existed between the onset in the young age and the sequentially relapsing rate (p = 0.06). Two cases with primary steroid resistance and 5 cases with frequent relapse or steroid dependence responded well to intravenous pulse therapy of cyclophosphamide, except one refractory case. No thrombotic episode was ever noted in our group. Regarding infectious complications, primary peritonitis occurred in one, pneumonia in one, and cellulitis in 6 cases during active nephrotic stage. Two mortality cases, one with E. coli-related necrotizing fasciitis and one from pneumonia, were noted. In brief, compared with children, adult patients with MCD had lesser high selectivity index for proteinuria, the same steroid-responsive rate (94%), but slower response, and significantly lesser relapsing rate. The intravenous pulse therapy of cyclophosphamide may be an alternative regimen for adult patients with steroid resistance or dependency. In addition, the Asian adult-onset MCD had younger age, male predominance, and lesser relapsing rate in comparison to those of the Western population.

Blood pressure and left ventricular hypertrophy in patients on different peritoneal dialysis regimens

OBJECTIVE

To examine the relation between the results of ambulatory 24-hour blood pressure monitoring (ABPM) and left ventricular mass index (LVMI), then to find the independent determinant for left ventricular hypertrophy (LVH) in peritoneal dialysis (PD) patients. Finally, to evaluate the differences in the clinical and cardiovascular characteristics between patients on continuous ambulatory PD (CAPD) and continuous cyclic PD (CCPD).

DESIGN

An open, nonrandomized, cross-sectional study.

SETTING

Divisions of nephrology and cardiology in a medical center.

PATIENTS

Thirty-two uremic patients on maintenance PD therapy (22 patients on CAPD, and 10 on CCPD) without anatomical heart disease or history of receiving long-term hemodialysis.

INTERVENTIONS

Home blood pressure (BP) and office BP were measured using the Korotkoff sound technique by sphygmomanometer. ABPM was employed for continuous measurement of BP. Echocardiography was performed for measurement of cardiac parameters and calculation of LVMI.

MAIN OUTCOME MEASURES

Multivariate logistic regression analysis was performed for independent determinant of LVH in PD patients. The differences in clinical and cardiovascular characteristics between CAPD and CCPD patients were compared.

RESULTS

Simple regression analysis showed positive correlations between LVMI and the duration of hypertension, ambulatory nighttime BP/BP load/BP load > 30%, serum phosphate, calcium-phosphate product, ultrafiltration (UF) volume, and percentage of UF volume during the nighttime. A negative correlation was noted between LVMI and dipping. In multiple regression analysis, the duration of hypertension was the only variable linked to LVMI. In multivariate logistic regression analysis, only ambulatory nighttime systolic BP load > 30% had an independent association with LVH. There were correlations between office/home BP and ambulatory 24-hour BP. In addition, CCPD patients had higher LVMI, UF volume during the nighttime, and percentage of UF volume during the nighttime than those of CAPD patients.

CONCLUSIONS

In this study, ambulatory nighttime systolic BP load > 30% had an independent association with LVH. Office and home BP measurements were correlated with ABPM in PD patients. The result that CCPD patients had a higher LVMI than CAPD patients may be due to a relative volume overload during the daytime in CCPD patients.

Randomized trial of enhanced anticipatory guidance for injury prevention

OBJECTIVE

To develop and evaluate an injury prevention anticipatory guidance training program for pediatric residents.

DESIGN

Thirty-one residents were randomly assigned to an intervention or control group. Both groups attended a 1-hour seminar about injury prevention and the American Academy of Pediatrics TIPP (The Injury Prevention Program) materials. The intervention group also received 5 hours of experiential instruction on injury prevention content and counseling skills (SAFE Counseling Framework). Families with infants from birth to age 6 months were enrolled in the study (N = 196); they were followed up until the child was aged 12 to 18 months. Data were collected by means of baseline and follow-up interviews, audiotapes of medical visits, parent exit surveys, and home observations.

SETTING

A hospital-based continuity clinic that serves families living in low-income, inner-city neighborhoods.

OUTCOMES

Physician counseling and parent satisfaction, knowledge, beliefs, and behaviors.

RESULTS

Parents seen by physicians in the intervention group received significantly more injury prevention counseling for 5 of the 6 safety practices, and they were significantly more satisfied with the help their physicians provided on safety topics. They were no less satisfied with their physicians' counseling on other anticipatory guidance topics. Parents' knowledge, beliefs, and home safety behaviors did not differ between the 2 groups.

CONCLUSIONS

The frequency and impact of pediatric counseling can be enhanced by experiential training that targets specific injury hazards. Because low-income families face many barriers to carrying out the recommended safety practices, supplemental strategies are needed to ensure safer homes.

Nonparametric and semiparametric trend analysis for stratified recurrence times

Recurrent event data are frequently encountered in longitudinal follow-up studies when the occurrences of multiple events are considered as the major outcomes. Suppose that the recurrent events are of the same type and the variable of interest is the recurrence time between successive events. In many applications, the distributional pattern of recurrence times can be used as an index for the progression of a disease. Such a distributional pattern is important for understanding the natural history of a disease or for confirming long-term treatment effect. In this article, we discuss and define the comparability of recurrence times. Nonparametric and semiparametric methods are developed for testing trend of recurrence time distributions and estimating trend parameters in regression models. The construction of the methods is based on comparable recurrence times from stratified data. A real data example is presented to illustrate the use of methodology.

Peritoneal scintigraphy for diagnosing periumbilical leakage in a patient on continuous ambulatory peritoneal dialysis

Continuous ambulatory peritoneal dialysis (CAPD) offers several advantages over hemodialysis for patients with end-stage renal disease; however, this technique also includes many documented complications. A case with clinical suspicion of dialysate leakage on CAPD was investigated by peritoneal scintigraphy using technetium-99m macroaggregated human albumin (99mTc-MAA). Peritoneal scintigraphy showed radiotracer accumulation over the periumbilical area at 2 hours 30 minutes after intraperitoneal infusion of 99mTc-MAA. Six hours of imaging revealed more apparent radioactivity at the same site. This study is to illustrate the simple diagnostic helpfulness of peritoneal scintigraphy in a patient with a CAPD-related structural defect.

Influence of laser posterior capsulotomy on anterior chamber depth, refraction, and intraocular pressure

PURPOSE

To evaluate the effect of neodymium:YAG (Nd:YAG) laser posterior capsulotomy on anterior chamber depth (ACD), intraocular pressure (IOP), and refraction, including spherical equivalent (SE) and various forms of astigmatism.

SETTING

Taipei Municipal Yang-Ming Hospital, Taipei, Taiwan.

METHODS

Fifty-three eyes of 46 patients with posterior capsule opacification were included in this prospective study. An Nd:YAG laser was used to perform posterior capsulotomy. Patients' ACD, IOP, and refraction were measured before the capsulotomy and 30 minutes, 1 week, and 1 and 3 months after.

RESULTS

There were no statistically significant differences in ACD, IOP, or SE (P =.201, P =.465, and P =.109, respectively). However, there were significant decreases in the magnitudes of refractive astigmatism and residual astigmatism after laser treatment (P =.012 and P <.001, respectively).

CONCLUSIONS

Although an Nd:YAG laser posterior capsulotomy did not significantly change ACD, IOP, or SE, it decreased the magnitudes of refractive astigmatism and residual astigmatism 1 week postoperatively. These stabilized thereafter.

Acute pyogenic iliopsoas abscess in Taiwan: clinical features, diagnosis, treatments and outcome

OBJECTIVES

To study the variations of aetiology in the patients with acute pyogenic iliopsoas abscess and identify the appropriate diagnostic modalities as well as therapeutic alternatives (e.g. extraperitoneal or retrofascial percutaneous catheter drainage, PCD) other than surgery.

METHODS

We carried out a retrospective review and analysis of 25 patients with acute pyogenic iliopsoas abscess in our institution from August 1988 to July 1998. Blood and urine cultures, imaging studies of the plain films of the abdomen (KUB), ultrasonography (echo) and computed tomography (CT scan) were performed in all patients. The therapeutic regimens included antibiotics only, PCD or aspiration, and surgery.

RESULTS

The male to female ratio was 7: 18. The mean age was 64 years old. Diabetes mellitus (64%) was the dominant predisposing or associated factor. The most common aetiological source was urinary tract infection (52%) with enteric micro-organisms (Escherichia coli: 44% and Klebsiella spp.: 24%). Nineteen patients (76%) had pain in the abdomen, flank or back. Six cases (24%) were classified as 'primary' abscess, and only two patients survived. Nine cases were treated with antibiotics alone, only four responded and the others expired. Of the 15 cases receiving PCD or aspiration, five cases received subsequent surgical drainage or nephrectomy and survived. Another one case of Clostridia gas gangrene received emergency fasciotomy and expired. The total mortality was extremely high (11/25, 44%).

CONCLUSIONS

We concluded that: (i) the aetiology of iliopsoas abscess may vary with the country of origin, with a preponderance of urinary tract infection in our Taiwanese series; (ii) a high index of suspicion is mandatory to enable early diagnosis of acute pyogenic iliopsoas abscess, particularly for older diabetic patients with fever, pain in the abdomen or flank, limp or flexion of the ipsilateral hip; (iii) CT scan can confirm the diagnosis and define the extent of the abscess; (iv) effective management should include appropriate antibiotic therapy and drainage of the abscess; (v) image-guided PCD should be tried first because of its low morbidity. However, should it fail, subsequent surgical drainage should be performed.

Effects of ciliary neurotrophic factor (CNTF) on protein turnover in cultured muscle cells

The goal of the study was to evaluate the mechanism by which ciliary neurotrophic factor (CNTF) regulated protein metabolism in skeletal muscle. L8 myotubes were cultured and effects of various times and doses of CNTF on protein synthesis and degradation were evaluated. Effects of CNTF on turnover of specific pools of proteins (myofibrillar and non-myofibrillar) were also evaluated. Protein synthesis was assayed by incorporation of radioactive tyrosine into muscle proteins. Degradation was assessed by release of labelled tyrosine from pre-labelled myotubes. Effects of CNTF on protein turnover were found to be time- and dose-dependent. CNTF (1 and 10 ng/ml) increased myofibrillar protein synthesis after 12 h of exposure but had no effect on non-myofibrillar protein synthesis. Longer exposures of CNTF (24 h) reduced non-myofibrillar protein synthesis and had no effect on myofibrillar protein synthesis. High concentrations of CNTF (10 and 20 ng/ml) reduced myofibrillar protein degradation but had no effect on degradation of non-myofibrillar proteins. To evaluate the mechanism by which CNTF exerts control of protein turnover, we completed a Northern blot for CNTF receptor alpha-subunit (CNTFRalpha). This was non-detectable via conventional northern analysis. Use of RT-PCR, however, confirmed expression of CNTFRalpha, albeit at a low level compared to rat skeletal muscle. This low expression of the receptor in L8 myotubes may explain the limited effect of CNTF in vitro compared to the larger effects typically detected in vivo. CNTF regulated protein turnover through control of protein synthesis and degradation. Effects were dose and timedependent. These observations may explain ability of CNTF to exert both anabolic and catabolic actions in vivo.

Digital retroilluminated photography to analyze posterior capsule opacification in eyes with intraocular lenses

PURPOSE

To compare the formation and rates of posterior capsule opacification (PCO) in eyes with poly(methyl methacrylate) (PMMA) versus silicone intraocular lenses (IOLs) using an in vivo objective method.

SETTING

Taipei Municipal Yang-Ming Hospital, Taipei, Taiwan, Republic of China.

METHODS

This prospective study comprised 40 eyes with senile cataract receiving phacoemulsification with capsular implantation of an IOL from March to April 1997. The uneventful surgeries were performed using the stop and chop method by the same surgeon. Twenty eyes received a PMMA IOL (Pharmacia 812A) and 20, a silicone IOL (AMO SI-30NB). One year later, digital retroillumination images taken with the EAS-1000 anterior segment analysis system (Nidek) were used to analyze posterior capsule transparency over the central 3.0 and 5.0 mm optic zones and evaluate the degree of PCO over the central and peripheral zones.

RESULTS

Over the central 5.0 mm optic zone, mean transparency of the capsule was 87.71% +/- 11.35% (SD) in the silicone group and 79.22% +/- 21.10% in the PMMA group (P = .17). Over the central 3.0 mm optic zone, the means were 97.17% +/- 5.96% and 86.32% +/- 19.60%, respectively (P = .048). Mean opacity in the central zone was 75.18 +/- 13.22 digital opacity units (OUs) in the silicone group and 80.24 +/- 7.93 OUs in the PMMA group (P = .18). The means in the peripheral zone were 88.49 +/- 18.47 OUs and 90.35 +/- 9.98 OUs, respectively (P = .71).

CONCLUSION

The posterior capsule in the silicone IOL group was more transparent than in the PMMA IOL group over the central 3.0 mm optic zone after 1 year follow-up.

Bone mineral acquisition in healthy Asian, Hispanic, black, and Caucasian youth: a longitudinal study

Ethnic and gender differences in bone mineral acquisition were examined in a longitudinal study of 423 healthy Asian, black, Hispanic, and white males and females (aged 9-25 yr). Bone mass of the spine, femoral neck, total hip, and whole body was measured annually for up to 4 yr by dual energy x-ray absorptiometry. Age-adjusted mean bone mineral curves for areal (BMD) and volumetric (BMAD) bone mineral density were compared for the 4 ethnic groups. Consistent differences in areal and volumetric bone density were observed only between black and nonblack subjects. Among females, blacks had greater mean levels of BMD and BMAD at all skeletal sites. Differences among Asians, Hispanics, and white females were significant for femoral neck BMD, whole body BMD, and whole body bone mineral content/height ratio, for which Asians had significantly lower values; femoral neck BMAD in Asian and white females was lower than that in Hispanics. Like the females, black males had consistently greater mean values than nonblacks for all BMD and BMAD measurements. A few differences were also observed among nonblack male subjects. Whites had greater mean total hip BMD, whole body BMD, and whole body bone mineral content/height ratio than Asian and Hispanic males; Hispanics had lower spine BMD than white and Asian males. The tempo of gains in BMD varied by gender and skeletal site. In females, total hip, spine, and whole body BMD reached a plateau at 14.1, 15.7, and 16.4 yr, respectively. For males, gains in BMD leveled off at 15.7 yr for total hip and at age 17.6 yr for spine and whole body. Black and Asian females and Asian males tended to reach a plateau in BMD earlier than the other ethnic groups. The use of gender- and ethnic-specific standards is recommended when interpreting pediatric bone densitometry data.