Some general methods for the analysis of categorical data in longitudinal studies

This paper is concerned with the analysis of multivariate categorical data from epidemiologic and clinical studies with longitudinal designs. An expository discussion of pertinent hypotheses for such situations is provided within the context of two relevant data sets. Appropriate large-sample tests of these hypotheses are developed through the application of weighted least squares to generate Wald statistics. These procedures are illustrated with extensive analyses of one of these data sets. In some situations, the resulting cross-classification of the response variables leads to extremely sparse frequency data, especially when the number of subjects is not large. For such repeated measurement designs in which a single variable is measured repeatedly over time, this paper considers the use of a generalized Mantel-Haenszel strategy for tests of marginal homogeneity (symmetry). These randomization model methods are illustrated for data in which the repeated measurement variable is reported on an ordinal scale. This paper also focuses on the available computing software to implement these methods within the version 5 release of the SAS system. The randomization model approach can be implemented within the FREQ procedure and a broad range of models and hypotheses can be investigated within the CATMOD procedure.

Cord serum bromide concentration: variation and lack of association with pregnancy outcome

Excessive maternal bromide exposure during pregnancy from drugs and occupation have been reported to have adverse effects on the fetus and newborn, including central nervous system depression at birth and possible teratogenicity. To define further fetal bromide exposure during pregnancy, we determined the cord serum bromide concentration in 1267 newborn babies born in Rochester, New York, during the 6-month period from January 1, 1984 to June 30, 1984. There was a normal distribution of the cord serum bromide concentration values (mean +/- SD = 8.6 +/- 2.6 mg/L; range 3.1 to 28.5 mg/L). The highest concentration was still significantly below the minimal bromide concentration associated with toxic effects (720 mg/L). There was no association between the cord serum bromide concentration and indices of fetal health including Apgar scores, presence of congenital malformations, and neonatal disposition. No mothers were taking significant amounts of bromide-containing drugs during pregnancy. The second highest cord serum bromide concentration (21.4 mg/L) was in a woman who was an amateur photographer and developed her own film, which required her to use chemicals containing bromide. Our results indicate that excessive fetal bromide exposure is rare and probably occurs only in the setting of maternal use of bromide-containing drugs or occupational exposure during pregnancy.

Effect of fish oil concentrates on hemorheological and hemostatic aspects of diabetes mellitus: a preliminary study

Fish oil concentrates (Max EPA) were given without other diet modification for eight weeks to five insulin-dependent diabetics and five healthy volunteers, in order to determine their effect on possible in vitro indices of thrombosis. Cholesterol, HDL, LDL, fasting blood sugar, hemoglobin A1c, platelet count, and the osmotic fragility of red blood cells were not significantly changed from baseline values after eight weeks of fish oil consumption. Serum triglyceride levels were lowered by the fish oil (diabetics 130 +/- 23 to 89 +/- 26 mg/dl: normals 107 +/- 16 to 57 +/- 5 mg/dl). Nine out of ten subjects required more arachidonic acid to aggregate their platelets, and six out of ten required more collagen. Whole blood viscosity at low shear rates was increased in diabetics before the fish oil ingestion, and was reduced both in normals and in diabetics after eight weeks of treatment. Before fish oil administration, the diabetics had higher levels of von Willebrand Factor (vWF) (208 +/- 31%) than did controls (117 +/- 26%). There was a statistically significant decrease of serum von Willebrand Factor both in diabetics (p less than 0.01) and in normals (p less than 0.05) after six weeks of treatment. Analysis of the multimeric composition of the vWF indicated that the vWF molecule was not altered. Addition of eicosapentaenoic acid (EPA) or crude fish oil to human umbilical cord endothelial cell cultures did not change vWF levels in the supernatant. Whether these changes in platelet aggregation, whole blood viscosity and vWF can actually be translated into an in vivo amelioration of the vascular complications in diabetes remains to be determined in a carefully controlled clinical trial.

Improved treatment of femoral shaft fractures in children. The "pontoon" 90-90 spica cast

In the past 15 to 20 years, little improvement has been made in the standard treatment of femur fractures in children. Children younger than two years of age or weighing less than 30 pounds are normally treated with skin traction or immobilized in a plaster cast or both. Older or heavier children are often treated with skeletal traction, followed by early or late application of spica cast in the neutral position. A method of spica cast treatment that immobilizes the limb in the 90-90 position using a reinforced cast incorporating a distal femoral traction pin--the pontoon spica--allows for early cast application and discharge from the hospital and encourages early motion of the knee joint. A series of 23 femur fractures in 21 patients were treated with this method. This series is compared with a series of 38 fractures treated with conventional methods. The follow-up period ranged from three to 24 months. The pontoon method provided better results in control of alignment than the conventional method, with no greater discrepancy in leg lengths than generally observed after skin traction and hip spica casts. The average hospital cost reduction was 73%, or approximately $13,334. There were no major complications with the pontoon method, which is now a standard treatment for femoral fractures in children.

Quantitative microscopy: I. A computer-assisted approach to the study of polymorphonuclear leukocyte (PMN) chemotaxis

A computer-assisted approach has been designed to analyze and quantitate polymorphonuclear leukocyte (PMN) chemotaxis. This approach involves a rapid, objective, and semiautomated (user-directed) image-analysis system that is video- and microscope-based. The entire system consists of a microvideo set-up that is put on line with a Digital DEC-LSI-11/73 microcomputer, interfaced with a Datacube analog-digital/digital-analog converter. Video signals of PMN movement are digitized by the system at a resolution of 240 pixels vertically by 320 pixels horizontally (at 256 gray levels) and stored in a 76,800-byte frame buffer. The digitized data are stored for later use or utilized immediately for image segmentation, image display, movement, and morphometric computations for each PMN in a maximum phase field (at 645 X high dry) of 50 PMNs at 10-second intervals. The digitized data are used for computation of cell perimeter, surface area, optical density, contour-ratio, position, speed, and direction of locomotion with the utilization of micro-image-analysis programs written in FORTRAN and MACRO assembly language, with the computer operating under RT-11/TSX+. The reliability, objectivity, and reproducibility of measurements made with this quantitative approach have been tested by comparing with manual-tracing measurements of PMN movement. A correlation factor of 0.99 has been obtained. However, the quantitative-microscopic approach is much faster, more objective, less tedious, and much easier to operate than the conventional manual-tracing method.

A computer-assisted image-analysis system for analyzing polymorphonuclear leukocyte chemotaxis in patients with diabetes mellitus

A computer-assisted image-analysis system that precisely tracks the cell movements of up to 50 polymorphonuclear leukocytes (PMNLs) was developed and used to quantitatively measure cellular chemokinesis and chemotaxis in normal individuals and in diabetic patients with hyperglycemia. The PMNLs were tested in Zigmond chambers with or without a gradient of 10(-7) M n-formylmethionylleucylphenylalanine (f-Met-Leu-Phe). Cellular movement was recorded on videotape by using a videocamera mounted on the microscope. The videotapes were analyzed by computer programs to calculate the speed and direction of each PMNL at 10-sec intervals. Average rates of chemokinesis were 19.6 microns/min without and 25.3 microns/min with f-Met-Leu-Phe. McCutcheon indices, which measure chemotaxis, were 0.01 without and 0.48 with f-Met-Leu-Phe. Similar values were observed in diabetic patients after fasting (average glucose, 217 mg/100 ml) and 2 hr after glucose challenge (average glucose, 309 mg/100 ml). These values demonstrate that PMNLs from diabetic patients with hyperglycemia move at normal rates and respond appropriately to f-Met-Leu-Phe.

Familial CHARGE syndrome: clinical report with autopsy findings

We report on a patient with CHARGE syndrome, as manifested by a coloboma of the optic nerve head, congenital heart defect (ASD, VSD, and parachute mitral valve), choanal atresia, severe growth retardation, genital hypoplasia, abnormal ears, cleft lip and palate, and pectus carinatum. His chromosomes were normal. He died at 19 months. His mother was short and had hearing impairment, choanal atresia, and a coloboma. We suggest that this represents evidence for dominant transmission of this disorder in this family. Other familial cases from the literature are reviewed.

Polymicrobial bacterial sepsis and defective neutrophil chemotaxis in an infant with cystic fibrosis

A 4 1/2-month-old, white girl was admitted to the hospital with respiratory distress and persistent polymicrobial bacteremia. Cystic fibrosis associated with malnutrition and a transient defect in peripheral neutrophil chemotaxis was diagnosed. This remarkable combination of presenting features in a patient with cystic fibrosis is the focus of this case report.

Hay-Wells syndrome

Hay-Wells syndrome is an autosomal dominant constellation of facial clefting, ankyloblepharon filiforme adnatum (fused eyelids), and ectodermal defects. Our patient, a child who had these unusual features at birth, led us to consider possible differential diagnoses based on clinical features and review of the literature.

Sweat bromide excretion in cystic fibrosis

Sweat reabsorption of bromide and chloride was studied in controls, obligate carriers of the cystic fibrosis gene, and individuals with cystic fibrosis. Sweat and serum ultrafiltrate concentrations of bromide and chloride were determined by an anion-exchange chromatographic method. The reabsorption of each ion was determined by the ratio of the sweat concentration to the serum ultrafiltrate concentration. Sweat bromide reabsorption paralleled chloride reabsorption in each of the groups. The mean bromide reabsorption ratio for 12 controls was 0.10 +/- 0.10 (range 0 to 0.26), for 11 obligate carriers 0.09 +/- 0.09 (range 0 to 0.24), and for 13 individuals with cystic fibrosis 0.86 +/- 0.26 (range 0.47 to 1.38). The mean chloride reabsorption ratio for the controls was 0.24 +/- 0.11 (range 0.06 to 0.45), for the obligate carriers 0.22 +/- 0.10 (range 0.10 to 0.45), and for individuals with cystic fibrosis 0.95 +/- 0.09 (range 0.76 to 1.1). Thus, there was a significant decrease in bromide reabsorption in individuals with cystic fibrosis compared with controls (P less than 0.001) and heterozygotes (P less than 0.001), which was similar for chloride. As with chloride reabsorption, no difference was found in bromide reabsorption between obligate carriers and controls, indicating that this measurement could not be used for heterozygote detection. In each of the three groups bromide reabsorption was greater than chloride reabsorption. This finding is consistent with a size-dependent anion channel in the sweat epithelial cell because bromide has a smaller hydrated radius than chloride.

The Boston bracing system for idiopathic scoliosis. Follow-up results in 295 patients

A total of 295 patients treated with the Boston bracing system with follow-up of at least 1 year after completion of bracing are reviewed. Pre-brace curves ranged from 20-59 degrees Cobb. Mean age at brace initiation was 13.2 years with a mean treatment time of 2.9 years and mean follow-up of 1.4 years. Mean best in-brace correction averaged 50% with correction averaging 23% at the initiation of weaning from the brace. By the time of brace discontinuance, average curve correction was 15%. At follow-up, average correction was 11%. A comparison of follow-up with pre-brace values of major curves showed that 49% were unchanged +/- 5 degree, 39% achieved final correction of 5-15 degrees, 4% achieved final correction of 15 degrees or more, 4% of patients lost 5-15 degrees, and 3% lost more than 15 degrees by the time of follow-up. Eleven percent of patients underwent surgery during the period of bracing; 1% had surgery during follow-up period. Correction and control of major curves with apexes below T8 and above L2 were best. A strong correlation between best, or initial in-brace correction, and follow-up correction was noted. Young age at the initiation of bracing and higher degrees of pre-brace curvature increased the incidence of surgery. Those curves that had corrected most at the end of bracing were most at risk for loss of correction after bracing. Partial compliance with brace wear appeared as effective as full-time wear. Boston braces without superstructure appeared to be as effective as braces with superstructure for curves with apexes below T7.

Treatment delays in the course of electroconvulsive therapy

Electroconvulsive therapy (ECT) is often delayed because the patient develops cognitive disturbances. The authors reviewed the charts of 45 depressed patients who received ECT and found that 25 patients developed cognitive dysfunctions severe enough to cause a delay in treatment. The development of organic symptoms causing delays in treatment was positively correlated with increased age and the presence of preexisting cognitive dysfunction, and the treatment delays led to longer periods of hospitalization. The authors emphasize the need for early identification of the causes of cognitive dysfunction after ECT and for careful selection of the treatment strategy for each patient to reduce the risk of adverse effects.

Cavum vergae. Association with neurologic abnormality and diagnosis by magnetic resonance imaging

Cavum vergae is a cavity posterior to the septum pellucidum whose clinical significance has previously been unclear. Ten children are described who presented with neurologic findings and were found to have a cavum vergae or cavum vergae and cavum septum pellucidum by brain computed tomographic (CT) scan. Of the ten patients, five had delayed development, four had macrocephaly, two had learning disabilities, two had abnormal electroencephalograms, and one had Apert's syndrome. No cases of cavum vergae were found in 50 children who had brain CT scans for head trauma. These observations suggest that cavum vergae is a nonspecific brain CT scan finding that can be associated with neurologic abnormality. The results of magnetic resonance imaging of one patient with cavum vergae are also described.

Ontogeny of neutrophil chemotaxis in fetal lambs

Ontogeny of neutrophil chemotactic response using endotoxin activated adult sheep plasma as a source of complement derived chemotactic factor was examined in fetal lambs of gestational age 120-150 days. (Gestational period in sheep is approximately 150 days.) Neutrophils from fetal lambs of gestational age 120-130 days failed to respond to this chemotactic factor whereas neutrophils from fetal lambs above 131 days of gestational age responded at levels comparable to adult values. Examination of neutrophil chemotaxis in older fetuses using a different chemotactic factor derived from mitogen stimulated adult mononuclear cells revealed a selective failure of fetal neutrophils to respond to lymphocyte-derived chemotactic factor in the presence of a normal response to complement derived chemotactic factor. Among prematurely delivered twin fetuses alterations in comparison with the first twin or age-matched controls in peripheral neutrophil count (increase) and in chemotaxis (increase or decrease) were noted in second of twins delivered greater than or equal to 20 min after the first lamb, suggesting an extreme sensitivity of neutrophil functions to a variety of influences, similar to that seen in humans.

A quantitative method for the analysis of cell shape and locomotion

A rapid, semiautomated system to quantitate and analyze leukocyte shape and locomotion was developed. Video images of moving leukocytes were obtained using a Vidicon camera mounted on a Nikon phase microscope. The video signal was either inputted directly, or indirectly via a video cassette recorder, to a Datacube video analog-digital, digital-analog converter. A Digital Equipment Corporation LSI 11/23 computer using the RT-11/TSX-Plus operating system and computer programs written in FORTRAN and MARCO assembly language permitted image segmentation, image display, and calculation of position, speed, direction of movement and orientation of each leukocyte at 10 s intervals. These data were stored on a winchester disk for subsequent evaluation of the leukocyte orientation, speed and direction of movement using statistical and graphical methods. The reproducibility of measurements made with the video system was tested by comparison with manual measurements; a correlation coefficient of 0.998 was obtained for the two methods. Rates of chemokinesis were then determined for unstimulated and chemokinetically stimulated polymorphonuclear leukocytes (PMNs) and found to average 12.8 micron/min and 18.1 micron/min, respectively. The high speed, ease of data analysis, and potential for multiparameter evaluation makes this system useful for directly evaluating leukocyte locomotion.

Closed Zickel nailing

A closed technique for Zickel nail insertion decreases morbidity, blood loss, and operative time. The Zickel intramedullary nail was originally developed as an open fixation device for fractures of the proximal third of the femur and subtrochanteric area. The open technique requires a lengthy incision, moderate blood loss, and time for insertion. For pathologic or impending pathologic fractures in sick patients, such a major operation is undesirable. The closed technique has been used successfully in five impending pathologic, three pathologic, and two traumatic subtrochanteric fractures. For these ten patients, the average operating time was one hour and 28 minutes with an average blood loss of 400 ml, a reduction of 40 minutes and 460 ml, respectively, over other available data. Time to ambulation and length of hospital stay are comparable to fractures treated openly. The closed technique is ideal for impending pathologic fractures, but may also be applicable to any pathologic or traumatic fractures that do not require an open procedure for alignment or supplementary fixation.

Anion-exchange chromatography to determine the concentration of chloride in sweat for diagnosis of cystic fibrosis

For the diagnosis of cystic fibrosis, we use the "Macroduct Sweat Collection System" (Wescor) to sample sweat, and anion-exchange chromatography to determine its chloride content. The chromatographic system consists of a Whatman Partisil SAX 10-microns column, an isocratic phosphate-buffered mobile phase, and ultraviolet detection at 200 nm. The sweat chloride concentrations of 10 individuals with cystic fibrosis ranged from 101 to 131 mmol/L (mean 111, SD 9 mmol/L). For 11 controls the values ranged from 13 to 54 mmol/L (mean 28, SD 11 mmol/L). We conclude that the procedure is reliable for the diagnosis of cystic fibrosis.

Anion-exchange chromatography to determine the concentration of chloride in sweat for diagnosis of cystic fibrosis

For the diagnosis of cystic fibrosis, we use the "Macroduct Sweat Collection System" (Wescor) to sample sweat, and anion-exchange chromatography to determine its chloride content. The chromatographic system consists of a Whatman Partisil SAX 10-microns column, an isocratic phosphate-buffered mobile phase, and ultraviolet detection at 200 nm. The sweat chloride concentrations of 10 individuals with cystic fibrosis ranged from 101 to 131 mmol/L (mean 111, SD 9 mmol/L). For 11 controls the values ranged from 13 to 54 mmol/L (mean 28, SD 11 mmol/L). We conclude that the procedure is reliable for the diagnosis of cystic fibrosis.