Comparison of the characteristics in hen and quail corneas as experimental models of refractive surgery. / Comparación de las características corneales en gallina y codorniz como modelos experimentales de cirugía refractiva.

AIM: To compare the histological, morphological and the biophysical measurements between hen and quail corneas, in order to determine which of them were better suited for use as an animal model for research into corneal refractive surgery. MATERIAL AND METHODS: A study was performed using the biophysical measurements of the cornea (curvature, thickness, refraction, and axial length) of 20 animals (10 hens and 10 quails). The corneas were then prepared for histological analysis under microscopy light. RESULTS: The analysis showed that both groups have the same number of corneal layers as the human cornea and with an evident Bowman's layer. The thickness of the hen cornea and axial length of the eye, 225.3±18.4µm and 12.8±0.25mm, respectively, were larger than that of the quail (P<.01 and P<.001, respectively). The radius of curvature for the hen central cornea, 3.65±0.08mm, was greater than that for the quail (P<.001), but the refractive power of each cornea was similar. The proportion of total corneal thickness of the hen stroma, 82.6%, was more similar to that of the human than was the quail stroma, 72.5%. Within the hen stroma, the density of keratocytes, 8.57±1.49 per 5,000µm(2), was about half that in the quail stroma (P<.005). CONCLUSIONS: Because of the large size of the hen cornea, the stromal thickness and proportional similarity of the corneal layers with human cornea, the hen maybe better than the quail as an alternative species suitable for use in studies of corneal refractive surgery.

Responses of the astroglia in sensory deprived olfactory bulb of developing rats.

The effects of unilateral olfactory deprivation on the glial population during the olfactory bulb development have been studied. The lack of sensory stimulation has been found to be related to an increase in gliofibrillary acid protein (GFAP) in the three layers of the deprived bulbs. This increase is due to the higher number of astrocytes in the deprived bulb, which is much more noticeable in the plexiform layer than in the other two, together with a hypertrophy of the reactive astrocytes resulting in an increase in the number and thickness of their prolongations. Our results demonstrate that sensory olfactory deprivation acts as other noxius agents on the CNS, causing gliosis in the olfactory bulb. This gliosis is revealed by astrocytic hyperplasia and hypertrophy.

Nutritional state alterations in children with acute lymphoblastic leukemia during induction and consolidation of chemotherapy.

The objective of the study was to determine if children with high risk acute lymphoblastic leukemia (ALL) exhibit higher frequency of alterations in nutritional state during the phases of induction and consolidation of chemotherapy than children with low risk ALL, based on the arm muscle area. The design was concurrent comparative cohorts. It was performed at pediatric hematology service of the Hospital General del Centro Médico Nacional "La Raza" and hematology service of the Hospital de Pediatría del Centro Médico Nacional "Siglo XXI". One hundred-five patients were incorporated into the study: 53 with high risk (HR) ALL and 52 with low risk (LR) ALL. Basal measurements of arm circumference and tricipital skinfold were surveyed monthly (for 3 months) by standardized personnel. Altered nutritional state during follow-up was defined as the loss of 10% or more of the arm muscular area (AMA) measured at diagnosis. Statistics of proportion analysis with a significance level of 0.05 and relative risk (RR) with confidence intervals (CI) were calculated. In the first month the RR was 0.77 (CI 0.31-1.87); the LR group was the most affected. In the second month the RR was 7.31 (CI 1.41-38.03); the most affected group was the HR. In the third month the RR was 1.77 (CI 0.60-4.92); the HR group was the most affected. High-risk patients show a higher frequency of nutritional state alterations reflected in AMA during the second month after diagnosis. This may be caused by the more aggressive chemotherapy received by these patients.

Malnutrition in childhood lymphoblastic leukemia: a predictor of early mortality during the induction-to-remission phase of the treatment.

BACKGROUND: Previous reports have shown that undernourished children with acute lymphoblastic leukemia (ALL) have a poorer long-term survival as compared with children with normal nourishment status. It has been shown that both the relapse and mortality rates of undernourished children with ALL are higher during the continuation phase of the chemotherapy and are apparently related to a poor tolerance of ablative chemotherapy. No previous articles have analyzed the early mortality rate of these patients. METHODS: We carried out a case-control study, and have studied the effect of severe malnutrition on the mortality of 17 children with ALL during the initial induction-to-remission phase of the treatment. These 17 cases were compared with 76 controls who had survived at least the phases of induction and consolidation. RESULTS: It was found that the chance of dying during the initial phase of the treatment was 2.6 times higher (confidence interval 95%: 0.55-11.89) in undernourished children with ALL than in those children with normal nourishment status. The risk of death increased with the severity of undernourishment (p = 0.04). CONCLUSIONS: These data confirm the prognostic value of malnutrition in children with ALL and suggest that undernourishment may also influence early mortality during the induction-to-remission phase of the treatment.

Factors associated with non-use of Pap test. A population survey.

BACKGROUND: Cervical cancer is the most important cancer in Mexican women. Early detection is possible by means of the Papanicolaou (Pap) test; however, the coverage in Mexico is low. METHODS: A cross-sectional survey was carried out in a representative sample of women from the Tlalpan area of Mexico City. Social, reproductive and health care factors associated with the lack of use of the Pap test with respect to adequate use and misuse were identified. Both bivariate and logistic regression analyses were used for the adjustment of variables. RESULTS: Of 1,215 women studied, 22.5% had never had a Pap smear, 42% had misused the test (< 90% of triennial performance), and 35.5% had adequately used the test (> or = 90% of triennial performance). The main factors related to the lack of use were the following: not knowing about the Pap test (ORa = 35.16, 95% C.I. = 17.4-70.9); having fewer than 6 years of education (ORa = 4.5, 95% C.I. = 2.5-8.4); women younger than 30 years of age (ORa = 3.4 95% C.I. = 2.3-5.1); use of contraceptives (ORa = 0.4, 95% C.I. = 0.2-0.8); history of sexually transmitted diseases (ORa = 0.3, 95% C.I. = 0.1-0.8), and the principal informant about the Pap test, i.e., the health services personnel (ORa = 0.02, 95% C.I. = 0.0008-0.05). CONCLUSIONS: The lack of use and the misuse of Pap smears vary importantly among the different social and reproductive factors. But the principal reasons for lack of use were not knowing about the Pap test and a low educational level. We propose a greater diffusion on the benefits of the test in the Mexican population, through massive means of communication and health services.

[Factors associated with peritoneal dialysis catheter failure in chronic renal insufficiency]. / Factores asociados a falla del catéter de diálisis peritoneal en insuficiencia renal crónica.

AIM: To determine the frequency, time of occurrence and factors associated with the failure of the permanent peritoneal catheter during dialysis in cases of chronic renal failure (CRF). MATERIAL AND METHODS: A retrospective cohort under a nested case control design was studied at a second level health care unit of the Instituto Mexicano del Seguro Social. A total of 149 catheters, double cushion straight Tenckhoff type, were evaluated in 74 patients with CRF due to diabetic nephropathy in 36/74 patients (49%). Information concerning functionality time and causes of catheter failure as well as the clinical and technical factors concerning insertion were obtained from the clinical chart. RESULTS: The cumulated time of dialysis was 814 months. Catheter failure occurred in 101 cases (68%): 67 due to obstruction, 24 due to infection, to leakage in 6 and to other causes in 4. Those of non-infectious origin were more frequent (p < 0.01). In the first month post-insertion there was a higher number of failures than after one month, (p < 0.0005). The global functionality of the catheter at one month, one and two years was 55%, 31% and 16%, respectively. There was a greater permanence of the catheters in continuous ambulatory peritoneal dialysis than in intermittent peritoneal dialysis (p = 0.02). CONCLUSIONS: It is concluded that the frequency of the peritoneal catheter failure was high; that the most frequent cause was due to non-infectious complications during the first month of insertion; and the factor associated to catheter failure was intermittent peritoneal dialysis as compared to continuous ambulatory dialysis.

[Diagnostic performance of immunologic tests in amebic liver abscess using receiver operating characteristic curves]. / Rendimiento diagnóstico de las pruebas inmunológicas en absceso hepático amibiano a través de curvas de características operantes del receptor.

Objectives. 1) To identify the tests of immunological diagnosis with a high diagnostic efficiency in amebic liver abscess. 2) To determine the ideal cutoff point for such tests. 3) To identify the influence degree of the antigen used over the test efficiency. Design. Comparative survey. Study units. Analysis of 24 articles identified in the medical literature about tests of immunological diagnosis in amebic liver abscess. Measurements. Starting from the articles, operating characteristics curves (ROC) were established derived from the test application to patients with amebic liver abscess. Results. A great variability in the diagnostic efficiency was identified between the various tests, even when the analysis was focused on the investigations of a specific test. It was not possible to conclude which test had a major degree of efficiency due to such variability. The cutoff level considered as relevant was higher than the one traditionally used for indirect hemagglutination and it had concordance with the one presently accepted for the fluorescence antibodies test. By maintaining steady the spectrum of the study patients and the type of test, variability among the tests persisted. This was due to the use of different antigens. Conclusions. A great variation in the diagnostic efficiency of the analyzed tests was identified. The variation source was the type of test, the antigen used and probably the illness spectrum.

[Frequency and risk factors associated with metronidazole therapeutic noncompliance]. / Frecuencia y factores de riesgo asociados al incumplimiento terapéutico con metronidazol.

OBJECTIVE: to determine the frequency and risk factors of non-compliance to oral metronidazole. STUDY DESIGN: comparative cross-sectional survey. STUDY UNITS: 111 patients who received oral metronidazole. SETTING CHARACTERISTICS: two medical units: one primary level unit and one secondary care unit of the Mexican Institute of Social Security. MEASUREMENTS: non-compliance was assessed by home interview and pill count. MAIN RESULTS: frequency of non-compliance was 55%. Risk factors for non-compliance were: female sex (OR = 3.0; p less than 0.05); side effects (OR = 3.1; p less than 0.05); low literacy (OR = 3.75; p less than 0.05). Stratified analysis showed no interaction between variables. CONCLUSIONS: frequency of non-compliance to metronidazole is high, and could affect the effectiveness of medical care. Female patients with low literacy and who suffer side effects are a high risk group for non-compliance.

[Classification by levels of clinico-epidemiological research designs]. / Clasificación en niveles de los diseños de investigación clínico-epidemiológicos.

The objective was to identify the characteristics of epidemiologic designs enabling their classification. A critical review of the literature in the clinical epidemiologic area was done to establish the main differences between designs. A meeting with experts to discuss this controversial topic and obtain criteria by consensus was organized. We propose an integral classification based on levels with two fundamental shafts: intervention and explanatory reasoning.

Satisfaction related factors of attendants to a medical research meeting.

OBJECTIVE: To assess satisfaction of attendants to a National Meeting on Medical Research in relation with the scientific quality and level of discussion of the research work. MATERIAL AND METHODS: An anonymous self-applied questionnaire was handed out to gather opinions about the scientific quality, level of discussion of the research work, and overall satisfaction with the meeting. The studied population included 400 physicians, all of them authors or collaborators of the research work presented. RESULTS: The rate of response was 62% (n = 249). Two hundred and twenty-four approved the scientific quality (90%), and 203 were satisfied with the level of discussion of research (88%); 239 were satisfied with the meeting as a whole (96%). The factors associated with dissatisfaction regarding the quality of the scientific meeting were the masculine gender (OR = 2.7, CI 95% = 0.8-9.l, p = 0.06), having an M.Sc. or Ph.D. degree (OR = 2.3, CI 95% = 0.9-5.5, p = 0.03), and having attending prior meetings more than twice (OR = 5.0, CI 95% = 1.5-18.4, p = 0.001). CONCLUSIONS: Most of the attendants were satisfied with the scientific quality and discussions of the research work. The masculine gender, having an M.Sc. or Ph.D. degree, and prior assistance were the factors associated with dissatisfaction of the scientific quality of the Meeting.

Validation of a prognostic index in the critically ill newborn.

OBJECTIVE: Elaborate and assess the degree of validity of a prognostic model for evaluating patients admitted to the Neonatal Intensive Care Unit (NICU). DESIGN: Cases and controls nested in a cohort. SETTING: NICU of two tertiary hospitals and another second level hospital. PATIENTS: The study was carried out in two phases. During the first phase (elaboration of a model), 336 newborns were studied; 112 belonged to the case group (dead patients) and 224 to the control group (live patients discharged). For the second phase (model validation), 300 patients were included that did not participate in the first phase, 100 cases and 200 controls. MEASUREMENTS: For each patient admitted to the study, clinical, paraclinical, perinatal and comorbidity factors were determined within the first 12 hours. Variables of statistical significance in the bivariate analysis were included in a logistic regression model with the objective of identifying a prognostic model. RESULTS: The variables that constituted the prognostic index were gestational age x birth weight, the paO2/FiO2 ratio x O2 saturation, arrest cardiac, major congenital malformations, septicemia and base excess. The model showed to have a sensitivity of 70% and a specificity of 91% during the elaboration cohort. In the validation cohort, sensitivity was 68% and specificity was 92%, a positive predictive value of 80%, negative predictive value of 85% and a correct classification rate was 84%. CONCLUSIONS: The Neonatal Mortality Prognostic Index (NMPI) developed in this study showed to be useful for the evaluation of hospital mortality for severely ill newborns admitted to NICU.

[Medical student traits associated with future success as physicians]. / Características del estudiante de medicina asociadas al éxito ulterior como médico.

OBJECTIVE: To identify the individual and family factors present during medical studies which are associated to success as a physician. RESEARCH DESIGN: Prolective case-control study. SETTING: Mexico City metropolitan area. STUDY UNITS: 120 physicians considered to be successful and 245 physicians who according to an established criteria were considered to be non-successful. MAIN MEASUREMENTS: A success-achieving index was constructed on the opinion of 134 physicians from different health-care institutions private and public. The index was composed by criteria such as being a member of prestiged academic associations; having a practice in third level institutions; having done postgraduate studies; being a professor with teaching and research activities; having obtained directive medical positions; and a high income at the moment of the interview. RESULTS: The main factors associated to success were: frequent attendance to cultural activities by the family of the subjects (OR = 5.2, IC 95% = 3.15-8.60, p = 0.00000001); the global score obtained during their medical studies, i.e. higher than 8.5 over 10 (OR = 4.43, IC 95% = 2.64-7.49, p = 0.00000001); and having been awarded recognitions, prizes or scholarships during their medical studies (OR = 4.3, IC 95% = 2.64-7.03, p = 0.00000001). A logistic regression model selected the cultural activities of the family, global score during medical studies and earning of recognitions, prizes and scholarships as independent variables associated to success achievement (p = 0.00001). CONCLUSIONS: Frequent cultural activities by the family and academic behavior were the factors present during medical studies which were associated to ulterior success as a physician.

[Characteristics of medical care related to autopsy authorization in a pediatric hospital]. / Características de la atención médica relacionadas con la autorización de autopsias en un hospital pediátrico.

OBJECTIVE: To identify some differences of patients and medical characteristics related to autopsy authorization. DESIGN: Observational, cross-sectional study. SETTING: Third-level medical care in a pediatric hospital. METHODS: A specific mortality questionnaire was analyzed by members of the mortality staff, because they reviewed deaths which occurred between January 1994 and December 1995. Descriptive statistic and non-parametric tests (X2) were calculated to analyze data. RESULTS: A total of 408 deaths were evaluated, in which 116 autopsies were done (28.4%). Children less than 18 months of age had the highest frequencies of autopsies (33.3%-30.7%). The patients referred by other units and the autopsy application done by a medical resident, had the highest frequencies of acceptance (32.5%, 35.3%, p < 0.05). The detection of diagnostic and therapeutic problems were related with high frequencies of autopsies (37.7%, 36% p < 0.05). CONCLUSIONS: The results show us that some medical care factors are related to higher frequencies of autopsies. It is important to consider them in order to increase the capacity of teaching that a postmortem study has.

[Instrument to measure quality of life based on daily performance in pediatric patients with leukemia]. / Un instrumento para medir la calidad de vida por medio del desempeño diario en pacientes pediátricos con leucemia.

The objective of this study was to determine the validity of a questionnaire to measure daily performance as an evaluation of quality of life in pediatric leukemia patients. A questionnaire of the daily activities of a child according to Lickert's criteria was done. A pilot survey was performed in patients without a chronic or disabling disease in order to assess its validity. The impression of the medical attendance of each pediatric patient with leukemia, of their daily performance, was compared with the results of the instrument. A trained nurse applied the questionnaire to 60 mothers of patients (29 female/31 male) as outpatients during the clinical review. Fifteen questionnaires were applied twice to evaluate its consistency. According to the results, 77% of the patients were in remission. 15% in relapse, and 8% during induction to remission. The mean age of the patients was 9 = 3.6 years, ranging from 2-16 years. One hundred percent of the patients obtained a satisfactory grade greater than 35 points. In conclusion, the questionnaire identified adequately the level of the daily performance in addition to the specific affected areas of the patients with leukemia. Our findings are that their level of performance is satisfactory and is not affected because of the disease or the phase of the treatment.

Wound healing following refractive surgery in hens.

The wound-healing response is critical to the outcome of refractive surgery and studying wound healing contributes to an understanding of the pathophysiology of other corneal injuries. Animal models allow research to be conducted with sufficient samples and under controlled parameters. We studied the hen to determine the healing process from clinical, biophysical, and biological standpoints after photorefractive keratectomy (PRK). PRK (-6.0 diopters) was performed in hen eyes. At 3, 6, 12, 24, 48, and 72 h and 5, 7, 15, 30, and 60 days postoperatively, we studied the clinical follow-up, objective measurements of light transmission (direct transmittance), apoptosis by TUNEL assay, proliferation by immunocytochemical analysis of 5-bromo-2'-deoxyuridine, and expression of alpha smooth muscle actin (SMA) in myofibroblasts in the corneas. Hen corneas reepithelialize quickly. Haze developed from 5 to 60 days after surgery and was correlated with the appearance and finalization of the expression of SMA. The direct transmittance of light was low during the first 15 days and improved at 30 and 60 days. TUNEL-positive cells were observed 3 h after surgery and the numbers decreased thereafter. Epithelial proliferation began at 12 h and was greater at 48 h, while stromal cell proliferation began at 24 h and was greater at 72 h. The hen cornea is anatomically similar to the human cornea, and the manner in which it heals is a good model for studying different surgical techniques and pharmacologic assays.

[Meta-analysis: an alternative method in clinical research]. / Meta-análisis: un método alternativo de investigación clínica.

Meta-analysis is a research method which allows for the grouping of results from different studies relating to the same topic. Its main objective is to increase the precision surrounding the original research problem and provide a possibility to answer to different questions. This method has been developed in the areas of physics and the social sciences and has been widely accepted within the medical field. Its main use in medicine is in relation to the evaluation of therapeutic measures, yet its application has extended to the evaluation of diagnostic tests, etiological and prognostic factors. In spite of its development, there are still persisting problems in research difficult to solve because of the heterogeneity of the grouped studies, the identification of the size of the relevant effect and of the application of the results in clinical practice. The growing use of this research method within the medical field calls for its comprehension, as well as the recognition of its advantages and limitations in order for its users to be capable of judging the validity of individual meta-analysis.