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PubMed2006

Retrospective measurement of the diffusion tensor eigenvalues from diffusion anisotropy and mean diffusivity in DTI.

A simple theoretical framework to compute the eigenvalues of a cylindrically symmetric prolate diffusion tensor (D) from one of the rotationally-invariant diffusion anisotropy indices and average diffusivity is presented and validated. Cylindrical or axial symmetry assumes a prolate ellipsoid shape (lambdaparallel=lambda1>lambdaperpendicular=(lambda2+lambda3)/2; lambda2=lambda3). A prolate ellipsoid with such symmetry is largely satisfied in a number of white matter (WM) structures, such as the spinal cord, corpus callosum, internal capsule, and corticospinal tract. The theoretical model presented is validated using in vivo DTI measurements of rat spinal cord and human brain, where eigenvalues were calculated from both the set of diffusion coefficients and a tensor analysis. This method was used to retrospectively analyze literature data that reported tensor-derived average diffusivity, anisotropy, and eigenvalues, and similar eigenvalue measurements were obtained. The method provides a means to retrospectively reanalyze literature data that do not report eigenvalues. Other potential applications of this method are also discussed.

Adult↗
PubMed1993

Detection of calcitonin and calcitonin gene-related peptide mRNA in human medullary thyroid carcinoma. A retrospective study.

In situ hybridization finds many applications in modern pathology. In many cases, special attention is paid to the processing of the tissues prior to in situ hybridization. In order to investigate the value of RNA in situ hybridization (RISH) in retrospective studies, we performed RISH for calcitonin and calcitonin gene-related peptide (CGRP)-I and -II mRNA in eight medullary thyroid carcinomas processed in 1981-1983. RISH was successful with radioactive calcitonin and CGRP-I probes. With biotinylated probes, only calcitonin-specific probes gave adequate results. The concentrations of CGRP mRNA were probably too low to be detected by non-radioactive RISH. The results of RISH were correlated with the immunohistochemical localization of the polypeptides. The results matched in all cases except one, where hybridization for calcitonin mRNA was found, but no immunoreactive calcitonin polypeptide. We conclude that RISH can be successfully used for retrospective analysis, even after long storage of tissue embedded in paraffin.

Calcitonin↗
PubMed2004

Retrospective diagnosis and subsequent prenatal diagnosis of Nijmegen breakage syndrome.

OBJECTIVE: We report on the retrospective diagnosis of Nijmegen breakage syndrome (NBS) confirmed by molecular genetic analysis and consecutive prenatal diagnosis in the same family. METHOD: Thirteen years after the death of their daughter due to fatal recurrent infections, a couple presented in our genetic counselling unit asking for the recurrence risk of their daughter's disease. Retrospective analysis of the medical record suggested that the girl might have suffered from NBS. Therefore, molecular genetic analysis for NBS was performed in the parents. RESULTS: After the diagnosis, NBS could be indirectly proven by molecular genetic heterozygosity testing of the parents, and a reliable prenatal diagnosis for a new pregnancy could be offered. In a following pregnancy, a massive hydrocephalus was diagnosed by ultrasound investigation. Amniocentesis was performed, and molecular analysis of the fetal DNA revealed homozygosity for the NBS1 mutation 657del5. CONCLUSION: The analysis of this family allows a further delineation of the prenatal NBS phenotype including hydrocephalus and dystopic kidneys that are helpful parameters to recognise NBS prenatally, also by ultrasound investigations in pregnancy. Additionally, we conclude that hydrocephalus might be more common in NBS patients than previously suggested.

Abnormalities, Multiple↗
PubMed1993

The effects of bedside pulmonary mechanics testing during infant mechanical ventilation: a retrospective analysis.

We examined the effects of regular bedside testing of pulmonary mechanics (PM) on the outcome of 468 acutely ill, mechanically ventilated neonates. During the first of two 18-month study periods, 217 infants were mechanically ventilated without the assistance of PM measurements. During the second 18-month period, 251 infants were ventilated with the assistance of at least daily PM measurements. Using data obtained from the PM tests, we adjusted the infants' ventilators to maintain tidal volume, inspiratory time, and pressure-volume loops within predetermined limits. With the exception of the PM measurements, given the limitations of retrospective analyses, both groups of infants received identical medical and nursing care. The infants ventilated with the assistance of PM testing developed fewer pneumothoraces (4.0%; 10/251) vs. no PM testing, 10.1% (22/217); P < 0.05 by Chi-square analysis]. Infants weighing less than 1,500 g ventilated with the assistance of PM measurements had less intraventricular hemorrhage (IVH) overall, most notably, less grades I and II IVH (total IVH-PM testing, 39.1% vs. no PM testing, 65.7%; P < 0.01; Grades I-II IVH-PM testing, 30.4% vs. no PM testing, 54.9%; P < 0.01). IVH incidence was decreased independent of pneumothorax occurrence. Survival rates, incidences of bronchopulmonary dysplasia, and durations of mechanical ventilation and hospitalization were similar. This retrospective analysis suggests that PM testing during infant mechanical ventilation reduces common acute ventilator-associated complications.

Bronchopulmonary Dysplasia↗
PubMed2005

On the prediction and prevention of myocardial infarctions: models based on retrospective and doubly censored prospective data.

Early detection of coronary heart disease (CHD) in its pre-clinical stages may offer a way to reduce the impact of this endemic disease on society. Coronary calcification accompanies the development of an atherosclerotic plaque, the pathological substrate of CHD, and its identification is currently possible by means of electron beam tomography (EBT). This is a non-invasive imaging test that quantifies the extent of coronary artery plaque calcification by means of a calcium score. In this study, we show that an age-sex based calcium score percentile (CS%) provides an invaluable predictor for myocardial infarction (MI), and examine how CS% is related to traditional risk factors. We study two separate groups of patients: 172 patients who underwent EBT screening after surviving an MI (retrospective group); and 676 asymptomatic subjects who were screened and followed for several years for the occurrence of an MI (prospective group). We use CS% with traditional risk factors in logistic regression models to: (1) compare patients in the retrospective and prospective groups, and (2) develop a mortality model for MIs that occurred in the prospective group. These logistic regressions are used to develop a joint model for the relative log-odds of an MI, which is non-linear in the covariates of the mortality model. We also use baseline covariates in the prospective group to fit an event-time regression model and estimate probabilities for 2 and 3 year exposure periods. The event-time regression provides independent estimates of the relative odds that are associated with risk factors. CS%, smoking, and their interaction were preeminent as predictors in the joint model for the relative odds of an MI and in the event-time regression, although the effects of smoking and CS% were generally subadditive. These models provide important information on the risks associated with elevated CS% levels.

Coronary Disease↗
PubMed1997

Emerging technological bases for retrospective dosimetry.

In this article we discuss examples of challenging problems in retrospective dosimetry and describe some promising solutions. The ability to make measurements by accelerator mass spectrometry and luminescence techniques promises to provide improved dosimetry for regions of Belarus, Ukraine and Russian Federation contaminated by radionuclides from the Chernobyl accident. In addition, it may soon be possible to resolve the large neutron discrepancy in the dosimetry system for Hiroshima through novel measurement techniques that can be used to reconstruct the fast-neutron fluence emitted by the bomb some 51 years ago. Important advances in molecular cytogenetics and electron paramagnetic resonance measurements have produced biodosimeters that show potential in retrospective dosimetry. The most promising of these are the frequency of reciprocal translocations measured in chromosomes of blood lymphocytes using fluorescence in situ hybridization and the electron paramagnetic resonance signal in tooth enamel.

Animals↗
PubMed1998

Neoadjuvant chemotherapy or primary debulking surgery in advanced ovarian carcinoma: a retrospective analysis of 285 patients.

OBJECTIVE: This study was aimed at comparison of neoadjuvant chemotherapy with primary debulking surgery in advanced ovarian carcinoma. METHODS: Retrospective analysis of 285 patients with advanced ovarian carcinoma treated between 1980 and 1997 was performed. RESULTS: In the period 1980-1988 all patients underwent primary debulking surgery and 82% were cytoreduced to less than 0.5 cm largest residual tumor mass (n = 112). Analysis of this group of patients showed that some subgroups of patients (e.g., Stage IV disease or a total metastatic tumor load of more than 1000 g prior to debulking surgery) had a poor survival despite cytoreduction to no or less than 1 g of total residual tumor load. The complication rate was high especially in the group with unfavorable prognosis (postoperative mortality, 6%). In the period 1989-1997 (n = 173) the patients were surgically evaluated to receive primary chemotherapy (43%) or primary debulking surgery (57%). Prognostic variables were similar for both treatment periods. The actuarial crude survival was higher in the second time period (3-year crude survival of 26% +/- 4. 3 and 42% +/- 4.6 for the first and second time periods, respectively; P = 0.0001). The postoperative mortality was 0% during the second time period. From 1993 on, the decision to give neoadjuvant chemotherapy or to perform primary debulking surgery in patients with clinically obvious metastatic disease was made with the help of an open laparoscopy (n = 77). Median duration of the laparoscopy, blood loss, and hospital stay due to this procedure were 25 min, 10 ml, and 2 days. Primary and interval debulking surgery was performed in 36 and 63% of this subgroup of patients, respectively. CONCLUSION: In this retrospective analysis over two different time periods, crude survival was higher when treating about half of the patients with advanced ovarian carcinoma with primary chemotherapy instead of primary debulking surgery. The role of neoadjuvant chemotherapy should be evaluated in a prospective randomized study.

Adult↗
PubMed2002

Assessment of mortality in patients enrolled in a risedronate clinical trial program: a retrospective cohort study.

Risedronate, a pyridinyl bisphosphonate, has been shown in large clinical trials to be effective in the prevention and treatment of osteoporosis. Analysis of safety data from these trials has shown that risedronate (2.5- and 5-mg doses) has an overall safety profile comparable to placebo during the course of the clinical trials. The clinical trials were powered appropriately to analyze the efficacy endpoints; however, patients were not systematically followed after completion of the clinical trials and therefore vital status for most of the patient cohort after the cessation of the clinical trials was unknown. In order to investigate further the safety profile of risedronate observed in the clinical trials database, we conducted a retrospective cohort mortality study among 7981 patients comprising the intent-to-treat population in three North American risedronate osteoporosis trials. No difference in all cause mortality was observed in patients receiving risedronate treatment compared with patients receiving placebo. There were also no differences between these groups in mortality due to all cancers, lung cancer, and gastrointestinal tract cancer. A trend toward lower cardiovascular mortality was observed in the risedronate groups compared with placebo; this difference was largely due to a significant reduction in stroke mortality in the active treatment groups. Follow-up mortality data in this retrospective cohort study demonstrate that treatment with risedronate has no effect on overall mortality rates.

Adult↗
PubMed1996

Retrospective failure analysis in laparoscopic hernia repair possible because of routine videodocumentation.

BACKGROUND: Studies performed to date show that laparoscopic hernia repair is superior to conventional procedures with regard to postoperative pain, complications, and duration of inability to work. METHODS: From August 1, 1992, to February 16, 1995, we performed 245 laparoscopic hernia procedures on 224 patients utilizing a transabdominal preperitoneal polypropylene mesh-plasty (TAPP). RESULTS: We observed in the first 100 patients a total of 21 postoperative complications in 20 patients (21%). We observed 3 hernia occurrences (3%) in this group. Due to careful video documentation of all procedures, retrospective analysis of operative failure was possible. Working on the complications occurring resulted in a modification of the procedure, leading to a standardization of the operative technique and to a rigorous reduction in the number of complications and recurrences. CONCLUSIONS: Video-assisted retrospective failure analysis is consequently an effective method to use to optimize the results of minimal invasive hernia repair.

Adolescent↗
PubMed1994

Retrospective study of the cystic fibrosis transmembrane conductance regulator (CFTR) gene mutations in Guthrie cards from a large cohort of neonatal screening for cystic fibrosis.

The cystic fibrosis transmembrane conductance regulator (CFTR) gene encodes a cAMP-activated chloride channel, and in individuals with both alleles of the gene mutated, symptoms of CF disease are manifest. With more than 300 mutations so far described in the gene the profile of mutant alleles in a population is specific to its ethnic origin. For an analysis with an unbiased recruitment of the CF alleles in neonates of similar origin (Normandy, France), we have retrospectively analyzed the Guthrie cards of affected newborns, diagnosed by the immunoreactive trypsinogen (IRT) assay. Analysis of the 27 exons of the CFTR gene using a GC clamp denaturing gradient gel electrophoresis (DGGE) assay has enabled us to identify over 96% of the mutated alleles. Two of these were novel mutations. We would like to propose this strategy as an efficient method of retrospective molecular genetic diagnosis that can be performed wherever Guthrie cards can be obtained. Knowledge of rare alleles could be a prerequisite for CF therapy in the future.

Base Sequence↗
PubMed1987

Retrospective evaluation of single photon emission computed tomography of the liver.

Retrospective analysis, including indications for examination, of 335 consecutive liver examinations of adults with single photon emission computed tomography performed at the Karolinska Hospital during the first eight months of 1981 has been carried out. 85.1% of the investigations were performed in tumour patients. This group underwent retrospective evaluation specifically regarding space occupying lesions of the liver with a minimum follow-up time of 3 years. An adequate follow-up of 87.4% was achieved. The study showed a sensitivity of 82.7% and a specificity of 93.9%. The positive and negative predictive values were 78.2% and 95.4%, respectively. 4.4% of the examinations were regarded as equivocal. Compared to previously reported values for planar liver scintigraphy derived from several different studies, the tomographic technique produced no increase of specificity or positive predictive value but a higher total accuracy, probably due to better clarification of the hepatic anatomy. The false positive, false negative and equivocal diagnoses were analysed and reported.

Adolescent↗
PubMed1987

Determination of the optimum period of interview for retrospective collection of data. An empirical study based on reported and documented outpatient contacts of depressive patients.

On the basis of reported and documented data on outpatient contacts of depressive patients, the reliability of data on the use of services, and the possibilities and sources of errors in the retrospective collection of data are presented and discussed. The results show an increase in errors the longer the period of inquiry is removed from the time of interview. The retrospective collection of data about ambulatory care more than 6 months ago has to be questioned from a reliability point of view. The correct dating of outpatient contacts succeeds substantially more reliably when questioned about periods of 3 months than about monthly periods, which leads to implications for the definition of patterns of care.

Ambulatory Care Facilities↗
PubMed1993

A retrospective cohort study on the incidence of hand dermatitis in nurses.

Data on the incidence and induction time of hand dermatitis are not available from the literature. To assist the planning of a prospective study on risk factors for hand dermatitis, a retrospective cohort study was performed in nurses and office employees to obtain a rough estimate of the incidence and induction time of hand dermatitis in these occupational groups. Data were collected by means of a self-administered questionnaire with validated questions on symptoms of hand dermatitis. The cohort consisted of 371 nurses and 111 office employees who were newly employed by a University Hospital between 1 January 1987 and 31 December 1988. Follow-up ended on 30 September 1989. Subjects who reported that symptoms had already occurred before entering the study were excluded for analysis on the incidence, leaving 298 nurses and 101 office employees for further analysis. Due to limitations of the retrospective study design, only half of the cases were able to report the exact month of occurrence of symptoms. Therefore only a rough estimate could be made of the incidence and induction period, assuming that the distribution of person-months of observation in cases with a known incidence date was equal to that of cases with unknown incidence dates. Thus, it was estimated that the overall incidence was 6.5 cases/1000 person-months in nurses and 1 case/1000 person-months in office employees. In nurses, 72% of the cases occurred within 3 months of follow-up.(ABSTRACT TRUNCATED AT 250 WORDS)

Cohort Studies↗
PubMed1992

Iopamidol in cardioangiography: a retrospective, multicentre study. Part II. Paediatric patients.

To evaluate the complication rate in paediatric cardioangiography with the nonionic contrast medium iopamidol data on 8,166 procedures were retrospectively collected in 12 centres. The overall complication rate was 3.78% (309/8,166). 3.44% were related to the procedure, and 0.34% to the contrast medium. The mortality rate varied with age. It was higher in patients less than 2 months (0.38%) than in patients greater than 2 months-2 years (0.06%) and in patients older than 2 years (0.03%). The total complication rate was higher than the one observed in a similar retrospective analysis performed in adult patients (1.89%). This difference is probably due to higher risk conditions of the younger patients. However the contrast medium related complication rate (0.34% vs 0.4%) and the mortality rate (0.11% vs 0.1%) were comparable, confirming the good tolerability of iopamidol in cardiac catheterisation also in paediatric patients.

Age Factors↗
PubMed1981

[Necessity and field of application of retrospective analyses in a time of prospective controlled studies (author's transl)].

Prospective controlled studies give the most reliable background for clinical decisions. To use them correctly, however, many strict premises have to be fulfilled that are often impossible in practice. If no research is conducted in these cases, however, that means disastrous dependence on one method. The main application of retrospective analyses is therefore in the sense of a second-best solution. Furthermore, retrospective consideration is a genuine necessity for medical research if you are interested in the critical reflection of your own work and in dealing with new problems.

Humans↗
PubMed1981

[The retrospective view of controlled clinical trials: is the subsequent formation of subgroups allowed? (author's transl)].

Additional data appearing in clinical trials can be evaluated only outside the protocol, i.e. retrospectively. An exclusion of patients before randomization is feasible, a withdrawal of patients after randomization is not allowed, but if unavoidable a "central blind review" should be introduced. No loss of patients should occur after the closing of the study. Differences in prognostic factors between groups of patients can be overcome by retrospective stratification. If there are different outcomes, a subsequent significance test at the 1% level is considered as well as a free interpretation.

Clinical Trials as Topic↗
PubMed1994

Premature craniosynostosis. A retrospective analysis of a series of 52 cases.

A retrospective analysis of a consecutive series of 52 cases with premature craniosynostosis is presented. Excellent functional, cosmetic, and social results could be achieved by resection of prematurely fused sutures and the creation of artificial growth sutures. Pronounced skull deformities have been corrected using the "basket handle", the "visor plasty", and the "T- bone" techniques or a combination of several of these skull form correction techniques. The surgical correction of the skull base by the "frontal advancement" technique in combination with orbitotomy was only necessary in 2 of our cases and could have been considered in 2 additional cases viewed retrospectively. Our results support the hypothesis that the primary cause of skull deformity is the premature closure of vault sutures and not a primary deformity of the skull base.

Child↗
PubMedDate not supplied

Knowledge engineering using retrospective review of data: a useful technique or merely data dredging?

The process of extracting the knowledge or rules for medical decision making is not an easy task. One approach to knowledge engineering is to carefully review how decisions were made in the past with the goal of extracting the rules. The purpose of this project was to use previously collected data from ICU patients to derive the rules for the definition of hemodynamic stability. 97 ICU patients between 9/9/86 and 7/29/90 were included in the analysis. All of these patients had adult respiratory distress syndrome. Their mechanical ventilation was managed by a set of computerized protocols. We retrospectively searched the HELP system database for instructions that were not followed due to hemodynamic reasons. For each patient, we also chose one randomly selected therapy instruction which was followed to act as a control. For each instruction we then selected the corresponding hemodynamic data set. The data was then used in a stepwise logistic regression to determine the rules used for defining hemodynamic instability. We found that several of the hemodynamic parameters we had anticipated to be important were not even measured most of the time. The blood pressures and heart rate were almost identical between the hemodynamicly stable and unstable data sets. We conclude that the decision making process used by physicians has great variation, both between and within physicians. This makes knowledge engineering using retrospective techniques such as this prone to error and probably not very fruitful.

Bias↗