Abstract 865: Impact of race and health insurance on delays in breast cancer diagnosis and treatment in the District of Columbia

Background: Delays in follow-up after breast cancer screening are thought to contribute to disparities in breast cancer outcomes. The primary objective of this study is to determine the impact of race as well as health insurance status on the diagnostic delay time, defined as the number of days from abnormal screening to definitive diagnosis. In addition, we analyze the effects of race and health insurance status on the treatment delay time, defined as the number of days from definitive breast cancer diagnosis to treatment initiation.

Methods: This is a retrospective study of 695 women examined for breast cancer between 1997 and 2009 at seven hospitals and clinics located in the District of Columbia. The outcomes of interest were the diagnostic delay time and the treatment delay time. We used full-factorial and main-effects ANOVA models to test for significant differences in these outcomes between African-American and white women with and without some type of health insurance.

Results: The mean diagnostic delay time was 37 days for insured white women, 76 days for uninsured white women, 75 days for insured African-American women, and 73 days for uninsured African-American women. In fitting a full-factorial ANOVA model, we found that insured white women had a significantly shorter delay in diagnosis than insured African-American women (p=0.0001) as well as uninsured white women (p=0.0007). Furthermore, a main-effects ANOVA model showed that after controlling for insurance status, African-American women had a mean treatment delay time of 45 days, which was significantly longer than the mean treatment delay time of only 17 days for white women (p<0.0001). Insurance status, however, had no significant effect on the treatment delay time after controlling for race (p=0.72).

Conclusions: Insured African-American women and uninsured white women waited more than twice as long to reach their definitive diagnosis than insured white women. African-American women also waited more than three times as long as white women for treatment initiation following definitive diagnosis. Lack of health insurance markedly decreased the speed of diagnostic resolution in white women, but having health insurance did not increase the speed of diagnostic resolution in African-American women. These results suggest that lack of health insurance may not be the primary barrier to optimal diagnostic resolution and treatment initiation in African-American women. It will be important to determine what other factors serve as the primary barriers, as well as if these delays affect the final breast cancer outcome for the patients.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 865.

Abstract 889: Evaluating the case definition of inflammatory breast cancer

Background: Inflammatory breast cancer (IBC) is recognized as an aggressive form of breast cancer requiring neoadjuvant chemotherapy. Although IBC affects only a small percentage of breast cancer patients, the estimated 4,810 new cases for 2009 exceeds the number of women diagnosed with other cancers, such as acute lymphocytic leukemia and chronic myelocytic leukemia (as reported by the American Cancer Society). Research on IBC is hampered by the absence of an agreed upon case definition. While the American Joint Committee on Cancer (AJCC) relies on clinical features (more than half of the breast being involved with redness, warmth and edema), the National Cancer Institute's Surveillance, Epidemiology and End Results (SEER) Program focuses on pathologic confirmation. This study was undertaken to determine whether the outcome of IBC differs among patients who meet IBC criteria by AJCC, SEER, and private practitioners to try to improve the case definition for research purposes.

Methods: This is a retrospective study of 121 patients in The George Washington University Medical Center IBC Registry who were classified as an IBC case by AJCC, SEER or private practitioners. We grouped these IBC cases into four epidemiological categories: (1) clinical-pathologic presentation of disease involving more than half of the breast, (2) clinical-only presentation of disease involving more than half of the breast, (3) clinical-pathologic presentation of disease involving less than half of the breast, and (4) clinical-only presentation of disease involving less than half of the breast. Note that Categories 1 and 2 meet AJCC criteria, while Categories 1 and 3 meet SEER criteria for IBC. We used an unadjusted Cox proportional hazards model to test the homogeneity of the progression-free survival (PFS) curves among these four epidemiological categories.

Results: Of the 121 IBC cases, 33.1% (n=40) were classified as Category 1, 16.5% (n=20) were Category 2, 25.6% (n=31) were Category 3, and 24.8% (n=30) were Category 4. Using Category 4 as the reference group, the Cox proportional hazards model yielded insignificant hazard ratios (95% CI) of 1.69 (0.82, 3.51), 0.80 (0.28, 2.28), and 1.98 (0.95, 4.12) for Categories 1, 2, and 3, respectively. Applying the Score test, we found no significant difference in the PFS curves among the four epidemiological categories (χ2=5.87, p=0.12).

Conclusions: The case definitions of IBC as proposed by the AJCC and SEER are inadequate. This study suggests that IBC as identified by private practitioners not meeting these criteria have the same poor prognosis as those meeting the case definitions of these national organizations. Preliminary laboratory studies support the conclusion that women with clinical evidence of IBC not involving half of the breast and with no documentation of involvement of the dermal lymphatics have the same disease as those meeting AJCC and SEER diagnostic criteria.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 889.

10-year follow-up of diabetes incidence and weight loss in the Diabetes Prevention Program Outcomes Study

BACKGROUND

In the 2.8 years of the Diabetes Prevention Program (DPP) randomised clinical trial, diabetes incidence in high-risk adults was reduced by 58% with intensive lifestyle intervention and by 31% with metformin, compared with placebo. We investigated the persistence of these effects in the long term.

METHODS

All active DPP participants were eligible for continued follow-up. 2766 of 3150 (88%) enrolled for a median additional follow-up of 5.7 years (IQR 5.5-5.8). 910 participants were from the lifestyle, 924 from the metformin, and 932 were from the original placebo groups. On the basis of the benefits from the intensive lifestyle intervention in the DPP, all three groups were offered group-implemented lifestyle intervention. Metformin treatment was continued in the original metformin group (850 mg twice daily as tolerated), with participants unmasked to assignment, and the original lifestyle intervention group was offered additional lifestyle support. The primary outcome was development of diabetes according to American Diabetes Association criteria. Analysis was by intention-to-treat. This study is registered with ClinicalTrials.gov, number NCT00038727.

FINDINGS

During the 10.0-year (IQR 9.0-10.5) follow-up since randomisation to DPP, the original lifestyle group lost, then partly regained weight. The modest weight loss with metformin was maintained. Diabetes incidence rates during the DPP were 4.8 cases per 100 person-years (95% CI 4.1-5.7) in the intensive lifestyle intervention group, 7.8 (6.8-8.8) in the metformin group, and 11.0 (9.8-12.3) in the placebo group. Diabetes incidence rates in this follow-up study were similar between treatment groups: 5.9 per 100 person-years (5.1-6.8) for lifestyle, 4.9 (4.2-5.7) for metformin, and 5.6 (4.8-6.5) for placebo. Diabetes incidence in the 10 years since DPP randomisation was reduced by 34% (24-42) in the lifestyle group and 18% (7-28) in the metformin group compared with placebo.

INTERPRETATION

During follow-up after DPP, incidences in the former placebo and metformin groups fell to equal those in the former lifestyle group, but the cumulative incidence of diabetes remained lowest in the lifestyle group. Prevention or delay of diabetes with lifestyle intervention or metformin can persist for at least 10 years.

FUNDING

National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK).

Alcohol Withdrawal Pharmacotherapy for Inpatients with Medical Comorbidity

Studies show that symptom-triggered dosing is best for treatment of alcohol withdrawal in patients on chemical dependence wards without other illness. On general medical hospital wards, withdrawal may be affected by comorbid medical illness. A clinical trial was undertaken to determine whether there is a difference between symptom-triggered (ST) and fixed-schedule (FS) dosing of lorazepam in patients hospitalized on general medical wards at a university medical center. One hundred eighty-three subjects were assessed by their nurses with the Revised Clinical Institute Withdrawal Assessment for Alcohol (CIWA-Ar) scale. Subjects in the ST arm received lorazepam doses based on CIWA-Ar score. Subjects in the FS arm received scheduled lorazepam with tapering over 4 days. Symptom-triggered dosing for alcohol withdrawal for general medicine inpatients results in less lorazepam given with similar reduction in CIWA-Ar scores for the first 2 days, but a higher proportion of protocol errors.

The Nord-Trondelag Norway Audiometric Survey 1996-98 : Unscreened thresholds and prevalence of hearing impairment for adults > 20 years

As supplement to a general health screening examination (HUNT-II), we conducted a puretone audiometry study in 1996-98 on adults (>20 years) in 17 of 23 municipalities in Nord-Trøndelag, Norway, including questionnaires on occupational and leisure noise exposure, medical history, and symptoms of hearing impairment. The study aims to contribute to updated normative hearing thresholds for age and gender, while evaluating the effects of noise exposure, medical history, and familial or genetic influences on hearing. This paper presents the unscreened hearing threshold data and prevalence of hearing impairment for different age groups and by gender. Valid audiometric data were collected from 62% (n=50,723) of 82,141 unscreened invited subjects (age-range 20-101 years, mean=50.2 years, SD=17.0 years). Two ambulant audiometric teams each conducted 5 parallel self-administered, pure-tone hearing threshold examinations with the standard test frequencies 0.25-0.5-1-2-3-4-6-8 kHz (manual procedure when needed). Tracking audiometers were used in dismountable booths with in-booth noise levels well within ISO criteria, except being at the criterion around 200 Hz. The data were electronically transferred to a personal computer. Test-retest correlations for 99 randomly drawn subjects examined twice were high. The mean thresholds recorded were some dB elevated from "audiometric zero" even for age group 20-24 years. As also found in other studies, this might indicate too restrictive audiometric reference thresholds. Males had slightly better hearing < or =0.5 kHz for all age groups. Mean thresholds were poorer in males > or = 30 years from > or =2 kHz, with maximal gender differences of approximately 20 dB at 3-4 kHz for subjects aged 55-74 years. Weighted prevalence data averaged over 0.5-1-2-4 kHz showed hearing impairment >25 dB hearing threshold level of 18.8% (better ear) and 27.2% (worse ear) for the total population--for males 22.2% and 32.0%, for females 15.9% and 23.0%, respectively. Mean hearing loss > or =10 dB at 6 kHz registered for both genders even in age groups 20-24 years may be partly due to calibration artefacts, but might possibly also reflect noise-related socio-acusis.

Valid across-group comparisons with labeled scales: the gLMS versus magnitude matching

Labeled scales are commonly used for across-group comparisons. The labels consist of adjective/adverb intensity descriptors (e.g., "very strong"). The relative distances among descriptors are essentially constant but the absolute perceived intensities they denote vary with the domain to which they are applied (e.g., a "very strong" rose odor is weaker than a "very strong" headache), as if descriptors were printed on an elastic ruler that compresses or expands to fit the domain of interest. Variation in individual experience also causes the elastic ruler to compress or expand. Taste varies genetically: supertasters perceive the most intense tastes; nontasters, the weakest; and medium tasters, intermediate tastes. Taste intensity descriptors on conventional-labeled scales denote different absolute perceived intensities to the three groups making comparisons across the groups invalid. Magnitude matching provides valid comparisons by asking subjects to express tastes relative to a standard not related to taste (e.g., supertasters match tastes to louder sounds than do nontasters). Borrowing the logic of magnitude matching, we constructed a labeled scale using descriptors unrelated to taste. We reasoned that expressing tastes on a scale labeled in terms of all sensory experience might work. We generalized an existing scale, the Labeled Magnitude Scale (LMS), by placing the label "strongest imaginable sensation of any kind" at the top. One hundred subjects rated tastes and tones using the generalized LMS (gLMS) and magnitude matching. The two methods produced similar results suggesting that the gLMS is valid for taste comparisons across nontasters, medium tasters, and supertasters.

Diagnosis of lower-extremity deep vein thrombosis in outpatients with musculoskeletal disorders: a national survey study of physical therapists

BACKGROUND AND PURPOSE

Prompt identification of outpatients who may have proximal lower-extremity deep vein thrombosis (PDVT) is important, in part, because of the risk of pulmonary embolism. The purposes of our study were to determine the degree of accuracy of physical therapists' estimates of the probability of PDVT in hypothetical patient vignettes and to determine whether physical therapists would contact the referring physician about the hypothetical patients' condition as recommended in published evidence.

SUBJECTS AND METHODS

A survey instrument consisting of 6 vignettes was sent to a nationally representative random sample of 1,500 physical therapists. The clinical decision rule developed by Wells and colleagues served as the gold standard for PDVT probability.

RESULTS

A total of 969 (65% response rate) physical therapists completed the survey. We found no evidence of nonresponse bias. For the 2 high-probability vignettes, 87% and 64% of the physical therapists underestimated the probability of PDVT. For the 2 high-probability cases, 32% and 27% of the physical therapists reported that they would not have contacted the referring physician. For the 2 moderate-probability cases, 15% and 30% of the physical therapists would not have contacted the referring physician. Therapist experience, certification status, place of practice, and region of the country did not explain the findings.

DISCUSSION AND CONCLUSION

The care of outpatients who are at risk for PDVT could potentially be improved by use of the clinical decision rule developed by Wells and colleagues, although more study is warranted.

Genetic and environmental influences on self-reported reduced hearing in the old and oldest old

OBJECTIVES

The aim of the present twin study was to estimate the relative importance of genetic and environmental factors in variation in self-reported reduced hearing among the old and the oldest old.

DESIGN

Self-reported hearing abilities of older twins assessed at intake interview in a population-based longitudinal survey.

SETTING

Denmark.

PARTICIPANTS

Twins age 75 and older identified in the population-based Danish Twin Registry in 1995. An interview was conducted with 77% of 3,099 individuals in the study population. In 1997 and 1999, a follow-up contact to the survivors was made and an additional 2,778 twins, age 70-76, were included in the study.

MEASUREMENTS

Reduced hearing was assessed by the same question in all interview waves. Heritability (proportion of the population variance attributable to genetic variation) was estimated using structural-equation analyses.

RESULTS

The prevalence of self-reported reduced hearing corresponded to previous studies and showed the expected age and sex dependence. Concordance rates, odds ratios, and correlations were consistently higher for monozygotic twin pairs than for dizygotic twin pairs in all age and sex categories, indicating heritable effects. Structural-equation analyses revealed a substantial heritability for self-reported reduced hearing of 40% (95% CI = 19-53%). The remaining variation could be attributed to individuals' nonfamilial environments.

CONCLUSION

We found that genetic factors play an important role in self-reported reduced hearing in both men and women age 70 and older. Because self-reports of reduced hearing involve misclassification, this estimate of the genetic influence on hearing disabilities is probably conservative. Hence, genetic and environmental factors play a substantial role in reduced hearing among the old and oldest old. This suggests that clinical epidemiological studies of age-related hearing loss should include not only information on environmental exposures but also on family history of hearing loss and, if possible, biological samples for future studies of candidate genes for hearing loss.

Image-guided, frameless stereotactic sectioning of the corpus callosum in children with intractable epilepsy

Corpus callosotomy is an effective neurosurgical procedure for children with intractable atonic or drop attack seizures. While this procedure has not changed significantly over the past three decades, some technical issues remain to be resolved. These include the intraoperative determination of the extent of the callosotomy, the need to stage the procedure, as well as side of approach of craniotomy. We report our 8-year experience with corpus callosotomy using a frameless stereotactic image-guided system (ISG Viewing Wand). Seventeen children with atonic seizures underwent sectioning of the corpus callosum. The mean patient age was 10.5 years. Six children underwent complete callosotomy while 11 underwent resection of the anterior two-thirds. MRI 3D reconstruction of the sagittal sinus and draining cerebral veins was undertaken in all cases. The side of the craniotomy was determined on the basis of favorability of the draining veins with respect to the extent of the callosotomy. The extent of the callosotomy was determined by intraoperative feedback using the ISG Viewing Wand((R)). Nine of 11 patients in the partial callosotomy group and 4 of 6 patients in the complete callosotomy group showed significant improvement in atonic seizures. We conclude that the use of frameless stereotaxy can function as an important adjunct in the planning and conduction of successful sectioning of the corpus callosum in children with intractable seizures.

Identification of the haemoglobin scavenger receptor

Intravascular haemolysis is a physiological phenomenon as well as a severe pathological complication when accelerated in various autoimmune, infectious (such as malaria) and inherited (such as sickle cell disease) disorders. Haemoglobin released into plasma is captured by the acute phase protein haptoglobin, which is depleted from plasma during elevated haemolysis. Here we report the identification of the acute phase-regulated and signal-inducing macrophage protein, CD163, as a receptor that scavenges haemoglobin by mediating endocytosis of haptoglobin-haemoglobin complexes. CD163 binds only haptoglobin and haemoglobin in complex, which indicates the exposure of a receptor-binding neoepitope. The receptor-ligand interaction is Ca2+-dependent and of high affinity. Complexes of haemoglobin and multimeric haptoglobin (the 2-2 phenotype) exhibit higher functional affinity for CD 163 than do complexes of haemoglobin and dimeric haptoglobin (the 1-1 phenotype). Specific CD163-mediated endocytosis of haptoglobin-haemoglobin complexes is measurable in cells transfected with CD163 complementary DNA and in CD163-expressing myelo-monocytic lymphoma cells.

Otoacoustic emissions and improved pass/fail separation using wavelet analysis and time windowing

A new method is presented for the purpose of improving pass/fail separation during transient evoked otoacoustic emission (TEOAE) hearing screening. The method combines signal decomposition in scales using the discrete wavelet transform, non-linear denoising and scale-dependent time windowing. The cross-correlation coefficient between two subaveraged, processed TEOAE signals is used as a pass/fail criterion and assessed in relation to the pure-tone, mean hearing level. The performance is presented in terms of receiver operating characteristics for a database of 5,214 individuals. The results show that the specificity improves from 68% to 83% at a sensitivity of 90% when compared with the conventional wave reproducibility parameter.

Cognitive development of term small for gestational age children at five years of age

AIM

To assess the relative significance for cognitive development of small for gestational age, parental demographic factors, and factors related to the child rearing environment.

METHODS

IQ of a population based cohort of 338 term infants who were small for gestational age (SGA) and without major handicap, and a random control sample of 335 appropriate for gestational age (AGA) infants were compared at 5 years of age.

RESULTS

The mean non-verbal IQ was four points lower, while the mean verbal IQ was three points lower for the children in the SGA group. The results were not confounded by parental demographic or child rearing factors. However, parental factors, including maternal non-verbal problem solving abilities, and child rearing style, accounted for 20% of the variance in non-verbal IQ, while SGA versus AGA status accounted for only 2%. The comparable numbers for verbal IQ were 30 and 1%. Furthermore, we found no evidence that the cognitive development of SGA children was more sensitive to a non-optimal child rearing environment than that of AGA children. Maternal smoking at conception was associated with a reduction in mean IQ comparable to that found for SGA status, and this effect was the same for SGA and AGA children. The cognitive function of asymmetric SGA was comparable to that of symmetric SGA children.

CONCLUSIONS

Our findings indicate that child cognitive development is strongly associated with parental factors, but only marginally associated with intrauterine growth retardation.

Factors associated with caregivers' choice of infant sleep position, 1994-1998: the National Infant Sleep Position Study

CONTEXT

The success and simplicity of the 1994 national "Back to Sleep" campaign to reduce sudden infant death syndrome provides an opportunity to study which elements determine whether a behavior will change in the desired direction in response to a public health intervention.

OBJECTIVE

To examine sociodemographic characteristics, motivation, and message exposure to ascertain which factors influenced a caregiver's choice of infant sleep position after implementation of the campaign.

DESIGN

Annual nationally representative telephone surveys conducted between 1994 and 1998.

SETTING

The 48 contiguous United States.

PARTICIPANTS

Nighttime caregivers of infants born within the 7 months prior to interview between 1994 and 1998. Approximately 1000 interviews were conducted each year.

MAIN OUTCOME MEASURES

The position the infant was usually placed in for sleep, sleep position recommendations received from specific sources, and reasons reported for position choice.

RESULTS

Between 1994 and 1998, prone placement declined from 44% to 17% among white infants and from 53% to 32% among black infants. Supine placement increased from 27% to 58% among white infants and from 17% to 31% among black infants. During this period, reports of supine recommendations from at least 1 source doubled from 38% to 79%. From 1995 to 1998, 86% of caregivers who placed the infant prone reported receiving only nonprone recommendations. Infant comfort was given as a reason for prone placement by 82% of these caregivers. In multivariate analysis, physician recommendation of "supine not prone" had the strongest influence and was associated with decreased prone placement (odds ratio [OR], 0.25 [95% confidence interval [CI], 0.16-0.39]) and increased supine placement (OR, 3.37 [95% CI, 2.38-4.76]). Recommendations from all 4 sources (the physician, neonatal nurse, reading materials, and radio/television) further increased the probability of supine placement (OR, 6.01 [95% CI, 4.57-7.90]). Other factors independently associated with increased prone and decreased supine placement included maternal black race, parity of more than 1, and living in a southern or mid-Atlantic state.

CONCLUSIONS

According to our study, as of 1998, approximately one fifth of infants were still placed prone, and only half were placed supine. Recommendations of supine placement during infancy by physicians at well-baby checks and by neonatal nursery staff and print and broadcast media have increased the proportion of infants placed supine. Caregiver beliefs regarding perceived advantages of prone sleeping should be addressed to attain further reduction in prone placement.

Factors associated with tympanostomy tube insertion among preschool-aged children in the United States

OBJECTIVES

Recurrent and persistent otitis media is often treated by tympanostomy tube insertion to ventilate the middle ear and restore hearing. This study examined the factors that predict which children are most likely to receive tympanostomy tubes through 3 years of age.

METHODS

Multiple logistic regression was conducted on data from a nationally representative sample of children (N = 8285).

RESULTS

By 3 years of age, 6.8% of US children had tubes inserted. Logistic regression indicated that after control for number of ear infections, children without any gaps in health insurance, who attended a day-care center, who were White, whose birth-weight was less than 1500 g, and who lived in the Midwest or South were significantly more likely to have tympanostomy tubes.

CONCLUSIONS

These data suggest that differences exist as to who receives tubes. Of particular concern are differences by race/ethnicity and continuity of health insurance coverage. With expansions in health care coverage to larger proportions of uninsured children, it will be important to monitor these programs to ensure that all children who may need tympanostomy tubes have access to them.

Healing After Photorefractive Keratectomy in Cat Eyes With a Scanning Mid-infrared Nd:YAG Pumped Optical Parametric Oscillator Laser

PURPOSE

To evaluate the healing characteristics of cat corneas treated with a new scanning mid-infrared laser system.

METHODS

Six adult cats were treated with 6-mm diameter photorefractive keratectomy (PRK) corrections. One eye in each animal was untreated as a control and the other was treated with either a -3.00 or -6.00 diopter ablation. The laser was a new Nd:YAG pumped optical parametric oscillator laser at 2.94 microm with a new scanning delivery system. The pulse width was 7 nanoseconds, the repetition rate was 10 Hz, the size of the laser spot on the eye was 1.0 mm, and the fluence was 150 mJ/cm2. Healing of the cat corneas was followed for 4 months. Slit-lamp and corneal topography evaluations were done at each follow-up examination. Histology was performed at the end of the study.

RESULTS

The corneal epithelium healed within 1 week. There was no stromal haze in any eye after the epithelium healed. After the first 2 weeks, slit-lamp examination could not identify which eye was treated. Corneal topography showed corneal flattening. Light microscopy at 4 months revealed normal epithelium and increased keratocyte density in the anterior third of the cornea. Electron microscopy showed discontinuities in the basement membrane and hemidesmosomes. The deep stroma and endothelium were normal.

CONCLUSIONS

Cat corneas treated with the new optical parametric oscillator laser healed normally with no adverse effects. Increased keratocyte activity in the anterior stroma was the only noticeable response besides the flattening shown by topography.

Histological Comparison of Corneal Ablation With Er:YAG Laser, Nd:YAG Optical Parametric Oscillator, and Excimer Laser

PURPOSE

To use histological techniques to assess and compare the ablation depth, local damage, and surface quality of corneal ablations by a Q-switched Er:YAG laser, an optical parametric oscillator laser at 2.94 microm, a long pulse Er:YAG laser, and a 193-nm excimer laser.

METHODS

Human cadaver eyes and in vivo cat eyes were treated with a 6.0-mm diameter, 30-microm-deep phototherapeutic keratectomy ablation and a 6.0-mm diameter, -5.00-D photorefractive keratectomy ablation. Human cadaver eyes were also treated with a 5.0-mm diameter, -5.00-D laser in situ keratomileusis (LASIK) ablation. Fluences and pulse widths used were 200 mJ/cm2 and 70 ns for the Q-switched Er:YAG, 150 mJ/cm2 and 7 ns for the optical parametric oscillator laser (OPO), 500 mJ/cm2 and 50 microseconds for the long pulse Er:YAG, and 160 mj/cm2 and 20 ns for the excimer laser. In the ablation rate study, 12 porcine eyes were ablated by the OPO laser with a range of layers and at different fluences ranging from 60 to 150 mJ/cm2, all using a 1.5-mm spot on the eye. The ablation depth of these acute ablations was evaluated by light microscopy examination.

RESULTS

In the acute damage study, light microscopy showed a thin surface layer in all samples with minimal thermal damage except on the long pulse Er:YAG corneas. Transmission electron microscopy revealed less than 0.3-microm surface damage for all specimens of both the optical parametric oscillator and the excimer laser samples with no evidence of collagen shrinkage. Transmission electron microscopy showed damage layers of 0.5 to 3 microm for Q-switched Er:YAG and 3 to 10 microm for long pulse Er:YAG. Scanning electron microscopy showed smooth surfaces in all eyes, although the excimer was the roughest. In the porcine eye study, ablations were produced in both PTK and PRK modes with the ablation rate per layer increasing with the fluence. At 120 mJ/cm2, the average ablation rate was 1.9 microm per layer.

CONCLUSIONS

The histology from the short pulse mid-infrared optical parametric oscillator laser at 2.94 microm was comparable to the 193-nm excimer with a smooth, damage-free, ablation zone when performing PRK and LASIK.

Photospallation: A New Theory and Mechanism for Mid-infrared Corneal Ablations

PURPOSE

A new mechanism for ablating corneal tissue is proposed, based on photospallation with short pulse mid-infrared (IR) laser radiation.

METHODS

By using a judicious combination of high absorption, short pulses, and low fluences, ablation with this process can potentially remove tissue in a highly localized manner with submicron collateral thermal damage characteristics similar to those achieved by excimer lasers. We provide a brief qualitative overview of aspects of the spallation process that distinguish it from the more familiar photoablation and photothermal mechanisms.

RESULTS

Results of preliminary parametric analysis based on one-dimensional models of thermoelastic expansion are summarized.

CONCLUSION

These preliminary calculations lend support to the conjecture that corneal tissue can be removed effectively with strongly absorbed nanosecond pulses from a mid-IR laser, using operational fluence levels of less than 200 mJ/cm2.

Minimizing Thermal Damage in Corneal Ablation with Short Pulse Mid-infrared Lasers

Photospallation is proposed as the primary mechanism behind our recent animal studies involving corneal ablation by nanosecond-pulse mid-IR laser beams. Following a brief summary of earlier work directed to refractive procedures in the mid-IR, a preliminary analysis is presented, based on simple one-dimensional models of thermoelastic expansion developed previously. The results of the analysis indicate that front surface spallation is consistent with the striking tissue ablation characteristics observed in our recent in vivo work with short pulse beams, including very small ablation rates and submicron thermal damage zones. This is attributed to the fact that spallation is a mechanical-rather than a thermal-mechanism, which allows tissue to be removed in small layers at fluences far lower than those used in the earlier corneal studies with mid-IR beams, typically under 200 mJ/cm2, resulting in minimal heating of tissue. Unlike prior work in the area of photospallation, we also suggest that the existing theoretical basis supports the use of nanosecond pulses as an effective approach to achieving controlled ablation in the presence of very high absorption. We further suggest that such domain of operation may be preferred over shorter pulses, both from a practical standpoint and to mitigate against potential damage from shock waves. © 1999 Society of Photo-Optical Instrumentation Engineers.

Frequent ear infections in association with child-care characteristics, based on the 1988 Child Health Supplement to the National Health Interview Survey

Using the 1988 Child Health Supplement to the National Health Interview Survey, we analysed the association between child-care characteristics and frequent ear infections among children under 6 years attending child care. We observed strong associations for 1- to 2-year-old children for variables involving exposure to many different children, including number of children in the main setting and one or more changes in child-care arrangement in the past year. No significant effects were observed for the children under 1 year, but sample sizes were small. Likewise, no strong associations were observed for the 3- to 5-year-old children, but they may have outgrown the detrimental effects of repeated respiratory tract infections.

Laryngeal basement membrane thickening is not a reliable postmortem marker for SIDS: results from the Chicago Infant Mortality Study

It has been suggested that laryngeal basement membrane (LBM) thickening is a pathognomonic postmortem marker for sudden infant death syndrome (SIDS) and is not seen in other causes of explained sudden infant death. To test this hypothesis, we evaluated longitudinal sections of the right hemilarynx taken through the midpoint of the true vocal cord from 129 SIDS cases and 77 postneonatal sudden infant death controls. Using a five-point semi-quantitative scale, maximum LBM thickness (LBMT) for SIDS cases and controls was not statistically different (mean, 2.39 + 0.69 and 2.40 + 0.77, respectively). Likewise, scores based on the average thickness along the entire basement membrane (i.e., "average" score), were not found to be different between SIDS cases and controls. Average and maximum LBMT increased with age in both SIDS cases and controls and were not different between SIDS cases and controls within each age interval. Similar trends in the distribution of maximum and average LBMTs were found between black and Hispanic SIDS and controls; the number of white/non-Hispanic infants was too low for meaningful comparisons. Maximum and average LBMTs were not different in SIDS cases and controls exposed to environmental tobacco compared with unexposed infants. The LBMTs also increased significantly with body weight and length in both SIDS cases and controls. Finally, there were no differences in LBMT in infants intubated prior to death compared with those who were not intubated. From these data, we conclude that LBMT is not pathognomonic of SIDS, is present or absent with equal frequency in SIDS and controls, increases with postnatal age, and does not correlate with passive smoke exposure. Therefore, LBMT should not be used to diagnose SIDS.

Outcome of epilepsy surgery in the first three years of life

PURPOSE

We analyzed our experience over a 6-year period with early-childhood patients who had undergone epilepsy surgery, and investigated the surgical outcomes.

METHOD

We reviewed the medical records of 23 children, ages 0-3 years, who underwent epilepsy surgery between 1991 and 1996.

RESULTS

Twenty children had partial seizures; two had infantile spasms; and one had generalized tonic-clonic seizures at onset. The mean age at onset of seizures was 4.7 months, and the mean age at time of surgery was 15.3 months. A total of 32 operations (21 focal cortical resections and 11 hemispherectomies) was performed. Five of 12 children with seizures secondary to a neuronal migration disorder had reoperations, including three who ultimately underwent complete hemispherectomy. The pathology consisted of hemimegalencephaly in three patients, focal cortical dysplasia (FCD) in eight, tuberous sclerosis in one, Sturge-Weber syndrome (SWS) in five, infarction in two, low-grade glioma (LGG) in three, and post-herpes simplex virus encephalitis (HSE) in one. The follow-up period ranged from 1 to 6.5 years (mean, 3.2 years) from patients' last operation. The seizure outcome according to Engel's criteria was class I in 12 patients, class II in three, class III in six and class IV in two.

CONCLUSIONS

Seizure outcomes after surgery were less favorable in infants with FCD than in those with SWS and LGG. Seizure outcome for the patients with hemispherectomies was excellent, compared with those who had focal cortical resections.

Interhemispheric interactions analyzed by coherence during flexor spasms

OBJECTIVE

We used coherence analysis to test for leading discharges on an ipsilateral right mesial temporal lesion in a 5 year old boy with flexor spasms.

METHOD

Digital EEG analysis with video-EEG telemetry was performed preparatory to epilepsy surgery.

RESULTS

Study of 10 spasms with head drop and subsequent flexion of both arms demonstrated an interhemispheric time lag with secondary bilateral synchrony, with a mean difference of 17 ms. The right hemisphere led. After a lesionectomy with resection of epileptic regions (performed with electrocorticographical guidance), the patient has been seizure-free for 4 years. Pathology confirmed a low-grade mixed glioma and cortical dysgenesis.

CONCLUSION

The coherence analysis demonstrated a pathway of secondary generalization, confirming that the lesional side was leading during ictal generalized discharges in flexor spasms.