Clinical Inaccuracy Research Articles

Sensitivity of Model-Based Predictions of Post-TKA Kinematic Behavior to Residual Errors in Ultrasound-Based Knee Collateral Ligament Strain Assessment.

Ultrasound-based ligament strain estimation shows promise in non-invasively assessing knee joint collateral ligament behavior and improving ligament balancing procedures. However, the impact of ultrasound-based strain estimation residual errors on in-silico arthroplasty predictions remains unexplored. We investigated the sensitivity of post-arthroplasty kinematic predictions to ultrasound-based strain estimation errors compared to clinical inaccuracies in implant positioning.Two cadaveric legs were submitted to active squatting, and specimen-specific rigid computer models were formulated. Mechanical properties of the ligament model were optimized to reproduce experimentally obtained tibiofemoral kinematics and loads with minimal error. Resulting remaining errors were comparable to the current state-of-the-art. Ultrasound-derived strain residual errors were then introduced by perturbing lateral collateral ligament (LCL) and medial collateral ligament (MCL) stiffness. Afterwards, the implant position was perturbed to match with the current clinical inaccuracies reported in the literature. Finally, the impact on simulated post-arthroplasty tibiofemoral kinematics was compared for both perturbation scenarios. Ultrasound-based errors minimally affected kinematic outcomes (mean differences < 0.73° in rotations, 0.1 mm in translations). Greatest differences occurred in external tibial rotations (-0.61° to 0.73° for MCL, -0.28° to 0.27° for LCL). Comparatively, changes in implant position had larger effects, with mean differences up to 1.95° in external tibial rotation and 0.7 mm in mediolateral translation. In conclusion, our study demonstrated that the ultrasound-based assessment of collateral ligament strains has the potential to enhance current computer-based pre-operative knee arthroplasty planning.

Incidence of postpartum hemorrhage based on the improved combined method in evaluating blood loss: A retrospective cohort study.

In view of the current clinical inaccuracies and underestimations of postpartum hemorrhage amount, this study aims to investigate the incidence, etiology, clinical characteristics of postpartum hemorrhage in different modes of delivery based on the combination of volumetric method, gravimetric method and area method in evaluating blood loss. This retrospective cohort study was conducted in Hangzhou Women's Hospital from January 2020 to June 2021, including 725 cases of postpartum hemorrhage among 18,977 parturients. Based on different modes of delivery, the participants were divided into three groups: vaginal delivery, forceps delivery, and cesarean section, for comparison. Using an improved combined assessment method for blood loss, we retrospectively analyzed a cohort of parturients with postpartum hemorrhage who underwent vaginal delivery, forceps delivery, or cesarean section and were hospitalized in Hangzhou Women's Hospital from January 2020 to June 2021. (1) Among the 18,977 parturients, 725 cases of postpartum hemorrhage occurred, with an incidence rate of 3.8%, and severe postpartum hemorrhage accounted for 0.4% of the cases. (2) The incidence of postpartum hemorrhage was significantly higher in the forceps delivery group than in the vaginal delivery group (χ2 = 19.27, P<0.001), while the incidence of severe postpartum hemorrhage was significantly higher in the cesarean section group than in the vaginal delivery group (χ2 = 8.71, P = 0.003). (3) The causes of postpartum hemorrhage were statistically different among the different delivery modes, with varying underlying factors (P<0.001). (4) Patients with postpartum hemorrhage in different delivery modes showed statistically significant differences in age, body mass index (BMI), birth weight, gestational age, gravidity, parity, the decline of postpartum peripheral blood hemoglobin concentration, and estimated blood loss (P<0.05). (5) The proportion of blood transfusion was significantly higher in the cesarean section group than in the vaginal delivery and forceps delivery groups (χ2 = 231.03, P<0.001). This study is a single-center retrospective study, which may have led to selection bias in case selection. Additionally, the implementation of the combined three blood loss assessment methods may not have been strictly followed in all cases. Moreover, due to the mixing of bleeding with amniotic and irrigation fluids, the accuracy of evaluation may have been affected, leading to the possibility of inaccuracy of blood loss. Forceps delivery and cesarean section increase the risk of postpartum hemorrhage, but forceps delivery does not significantly increase the incidence of severe postpartum hemorrhage. Uterine atony remains the leading cause of postpartum hemorrhage, while birth canal laceration and placental factors are the second most common causes of postpartum hemorrhage in forceps delivery and cesarean section, respectively. In this study, the volumetric method, gravimetric method and area method were combined to quantitatively assess postpartum hemorrhage amount. The combined method has strong clinical practicability and is less affected by subjective factors, although it also has limitations. In the future, we still need to focus on the early prediction and identification of postpartum hemorrhage, and further improve the quantitative assessment of postpartum blood loss.

A Literature Review of Dorsal Root Entry Zone Complex (DREZC) Lesions: Integration of Translational Data for an Evolution to More Accurate Nomenclature.

The purpose of this translational review was to provide evidence to support the natural evolution of the nomenclature of neuromodulatory and neuroablative radiofrequency lesions for pain management from lesions of individualized components of the linear dorsal afferent pathway to “Dorsal Root Entry Zone Complex (DREZC) lesions.” Literature review was performed to collate anatomic and procedural data and correlate these data to clinical outcomes. There is ample evidence that the individual components of the DREZC (the dorsal rami and its branches, the dorsal root ganglia, the dorsal rootlets, and the dorsal root entry zone) vary dramatically between vertebral levels and individual patients. Procedurally, fluoroscopy, the most commonly utilized technology is a 2-dimensional x-ray-based technology without the ability to accurately locate any one component of the DREZC dorsal afferent pathway, which results in clinical inaccuracies when naming each lesion. Despite the inherent anatomic variability and these procedural limitations, the expected poor clinical outcomes that might follow such nomenclature inaccuracies have not been shown to be prominent, likely because these are all lesions of the same anatomically linear sensory pathway, the DREZC, whereby a lesion in any one part of the pathway would be expected to interrupt sensory transmission of pain to all subsequent more proximal segments. Given that the common clinically available tools (fluoroscopy) are inaccurate to localize each component of the DREZC, it would be inappropriate to continue to erroneously refer to these lesions as lesions of individual components, when the more accurate “DREZC lesions” designation can be utilized. Hence, to avoid inaccuracies in nomenclature and until more accurate imaging technology is commonly utilized, the evidence herein supports the proposed change to this more sensitive and inclusive nomenclature, “DREZC lesions.”

Analytical Comparison between Spectrophotometer and Portable Glucometer for Measurement of Blood Glucose in Horse

Objective: Analytical methods comparison for the determination of blood glucose are essential in clinical laboratory practice as it improves the quality of health care through accurate and reliable clinical decision making. Therefore, the study was done to assess the analytical performance between point-of-care glucometer named easy touch glucose monitoring system and spectrophotometer named EMP-168 biochemical analyzer for blood glucose determination in horse. Results: Twenty paired samples from horses visiting SPANA clinic of college of veterinary medicine and agriculture Addis Ababa University was used. Data obtained from both instruments was compared. The results showed that the mean value of blood glucose concentrations were higher in glucometric method (106 mg/dl) than the spectrophotometric (73 mg/dl) with the calculated t-statistic significantly different p-value of 0.000. This study showed the clinical inaccuracy of the glucometer over the spectrophotometer

REPRODUCIBILITY OF LINEAR ALVEOLAR RIDGE MEASUREMENTS IN 2 DICOM CBCT VIEWING SOFTWARE PROGRAMS: A PILOT STUDY

Objectives The aim of the study was to determine if the same critical measurement of vertical alveolar ridge height at a dentoalveolar implant recipient site can be measured to the same degree of accuracy from cone beam computed tomography (CBCT) volumetric data with 2 very popular but different commercially available DICOM (Digital Imaging and Communications in Medicine) imaging software: InVivoDental (Anatomage, San Jose, CA, USA) and CareStream 3D (CareStream Dental, Rochester, NY, USA). To determine the degree of precision of alveolar ridge height measurements, we used 2 different DICOM imaging software: InVivoDental (Anatomage, San Jose, CA, USA) and CareStream 3D (CareStream Dental, Rochester, NY, USA). Methods Fifteen maxillary and 15 mandibular posterior implant sites were selected from CBCT patient records (institutional review board # 5160188) at the Loma Linda University School of Dentistry (Loma Linda, CA). The sites also had radiographic stents with directional guide holes for the proposed implant. Two observers, one for each software, used the measurement tools to record the measurements. The measurement line was along the guide hole path from the peripheral crestal cortex to the peripheral cortex of the sinus floor (maxilla) and to the superior mandibular canal border (mandible). The examiners were calibrated on identifying the inferior maxillary sinus border, superior mandibular canal border, and the radiographic stent guide holes. The 2 examiners then independently performed measurements in the paracoronal and parasagittal planes. The means of the 4 independent linear measurements at each of the implant locations in each software were tested with the GraphPad QuickCalcs t test calculator for paired samples at the 5% level of significance. Results There was no difference (P > .05) between linear measurement distances made in 2 different DICOM compliant 3D viewer software when comparing only sagittal, only coronal, or combined sagittal and coronal implant recipient site measurements in the posterior maxilla or mandible. Discussion No difference can be expected when making measurements from a CBCT scan when data are converted to the DICOM file format and measured with the 2 programs used in this study. However, to obtain agreement, the measurement process is very rigorous. Any variation in the technique could cause variation and clinical inaccuracy. Future studies are suggested to determine if proprietary volumetric data set file formats or other DICOM third-party software would also demonstrate the same degree of measurement comparability. In support of such research, the data from this study suggest that if clinicians make measurements relative to predefined reference points, then a similar degree of accuracy in the measurements can be expected. Conclusions There is no difference in vertical linear measurements of implant sites in the posterior maxilla or the posterior mandible when measuring DICOM-compatible volumetric data sets with either InVivoDental or CareStream viewer software.

Effect of different pre-analytical conditions on plasma lactate concentration.

IntroductionPlasma lactate is a frequently used and important parameter for medical decision making. To setup a pre-analytical algorithm, we aimed to investigate the influence of different test tube additives, aliquoting, ice storage and haemolysis on plasma lactate concentrations for possible sparing critically ill (ICU) patients of additional blood drawing.Materials and methodsIn our study (N = 177), lactate concentration and haemolysis index (HI) were measured in aliquoted (AHP) and unaliquoted (HP) Li-heparin, NaF/K3EDTA and NaF/KOX plasma, centrifuged within 15 minutes after venipuncture, on Cobas c501 analyzer. Differences were tested using the Wilcoxon’s test and Passing-Bablok regression. Clinical accuracy of results was assessed in 107 ICU patients based on reference interval and clinical decision limits.ResultsLactate concentrations did not differ in NaF/K3EDTA and NaF/KOX plasma (P = 0.855). No clinically significant difference of AHP compared to NaF/K3EDTA lactate was found (y = 0.13 (0.08 to 0.19) + 1.02 (0.99 to 1.08) x) if samples were aliquoted within 30 minutes after venipuncture. On contrary, lactate concentrations in HP showed significant proportional difference (y = 0.07 (- 0.12 to 1.24) + 1.37 (1.22 to 1.56) x) and were clinically incorrect in 14% of patients. Transport in ice bath increases HI in NaF/K3EDTA (P < 0.001), but without influencing lactate results compared to room temperature (y = 0.03 (- 0.06 to 1.00) + 1.05 (0.99 to 1.11) x).ConclusionsLactate determination in HP is unacceptable because of high proportional error and high risk of clinical inaccuracy compared to NaF/K3EDTA. If pre-analytical conditions are met, AHP, NaF/K3EDTA and NaF/KOX plasma can be used interchangeably. Aliquoted Li-heparin samples alow measurement of other biochemical tests from a single tube and can spare ICU patients from additional blood drawing. Storage in ice bath provides no additional stabilization in NaF/K3EDTA tubes.

Clinical Impact of Targeting Inaccuracy Due to Distortion of the Leksell Stereotactic Frame

Background: Distortion of the Leksell stereotactic frame can occur during surgical and radiosurgical frame-based procedures. The targeting accuracies of surgical procedures such as DBS surgery or frame-based biopsy, or Gamma Knife radiosurgical procedures, are related to the stereotactic frame that is commonly referred to a non-deformable referential system. Objective: To evaluate the clinical impact of frame distortion on accuracy of targeting in various stereotactic procedures. Methods: We studied the influence of increasing levels of distortion of the Leksell frame both on surgical procedures using the stereotactic arch, and on radiosurgical procedures with the Gamma Knife. For surgical procedures we applied the Target Simulator of Elekta to a frame submitted to different levels of frame distortion, and we measured the modifications of accuracy of targeting. For radiosurgical procedures the Leksell frame was applied on an anthropomorphic phantom and modifications of target coordinates were measured by an imaging method using the stereotactic CBCT of the Gamma Knife ICON. Results: For surgical procedures, we found a linear relation between the amount of the frame distortion and the extent of the deviation from the stereotactic target using the stereotactic arch (R2 = 0.99709). The level of bending of the frame is also linearly related to the level of inaccuracy of stereotactic targeting based on acquisition of MRI and CTscan with the Elekta imaging boxes (R2 = 0.96825). The inaccuracy of targeting related to frame bending can be avoided by a systematic control at the end of frame placement and by the use of the CBCT of the Gamma Knife Icon. Conclusion: Distortion of the frame is a significant source of clinical inaccuracy of targeting for stereotactic procedures. Frame bending must be checked after each frame placement and corrected if needed to avoid targeting inaccuracy during stereotactic surgery and radio-surgery procedures.

Toward Successful Implementation of Speech Recognition Technology: A Survey of SRT Utilization Issues in Healthcare Settings.

To evaluate physician utilization of speech recognition technology (SRT) for medical documentation in two hospitals. A quantitative survey was used to collect data in the areas of practice, electronic equipment used for documentation, documentation created after providing care, and overall thoughts about and satisfaction with the SRT. The survey sample was from one rural and one urban facility in central Missouri. In addition, qualitative interviews were conducted with a chief medical officer and a physician champion regarding implementation issues, training, choice of SRT, and outcomes from their perspective. Seventy-one (60%) of the anticipated 125 surveys were returned. A total of 16 (23%) participants were practicing in internal medicine and 9 (13%) were practicing in family medicine. Fifty-six (79%) participants used a desktop and 14 (20%) used a laptop (2%) computer. SRT products from Nuance were the dominant SRT used by 59 participants (83%). Windows operating systems (Microsoft, Redmond, WA) was used by more than 58 (82%) of the survey respondents. With regard to user experience, 42 (59%) participants experienced spelling and grammatical errors, 15 (21%) encountered clinical inaccuracy, 9 (13%) experienced word substitution, and 4 (6%) experienced misleading medical information. This study shows critical issues of inconsistency, unreliability, and dissatisfaction in the functionality and usability of SRT. This merits further attention to improve the functionality and usability of SRT for better adoption within varying healthcare settings.

265 MYELODYSPLASTIC SYNDROME FOLLOWING ESSENTIAL THROMBOCYTOPENIA IN HYPERTENSION - A CASE REPORT

Myelodysplastic Syndrome (MDS) is a disorder of haemopoietic stem cell. Since, it has not been commonly observed in Pakistan, thus, this case study is to understand the scientific and therapeutical comprehension of MDS. An 81 year old male hypertensive patient was presented in a private hospital of Islamabad, Pakistan, with anemia. On medical investigation the physician prescribed him, multi-vitamins OD for a month; injection G-CSF 300mcg once a week; Molgramostim 300µg on every alternate day for 3 weeks; Thalidomide 100mg OD with Alprazolam 0.5mg at night for 4 weeks and 5’-azacytidine for a month. Clinical and pharmaceutical inaccuracies were observed. Moreover; the high cost and long term therapy are major obstacles to cure this disease. Therefore, affordable method and short-term effective therapy and reduced cost of drugs will help to cure the disease in more efficient way and in less time with more promising results.

The Clinical Inaccuracy of Estimated Flow in Continuous Flow Ventricular Assist Devices

Purpose The HeartMate II® ventricular assist device (HM-VAD) provides continuous flow support and its display monitor reveals an estimate of flow. Whether this flow-estimate predicts cardiac output (CO) in the clinical setting remains unclear. We sought to determine the accuracy and clinical reliability of the estimated flow in determining CO in patients (pts) with an HM-LVAD. Methods and Materials Cardiac catheterization (RHC) was performed in 25 pts with an HM-VAD. Pts with significant aortic insufficiency or presumed HM-VAD thrombosis were excluded. The average of 3 consecutive thermodilution CO measurements was made while simultaneously recording the flow-estimate on the HM-LVAD display monitor. Results The indication for RHC was per clinical protocol (n=19) or right heart failure (n=6). The mean HM-VAD parameters were: speed 9600 rpm, flow 5.7±0.8 l/min, power 6.9±0.7 watts, and pulsatility index 4.8±0.8. A weak correlation was seen between CO and estimated flow (r=0.38; p=0.05) with the poorest correlation seen in those with a lower cardiac index ( figure 1 ] Conclusions Flow estimates correlate poorly with cardiac output and should not be relied upon as a surrogate for CO in HM-VAD pts. A low threshold for invasive CO measurement is warranted particularly in those whose clinical condition is consistent with a low CO state.

Factors affecting the accuracy of buccal alveolar bone height measurements from cone-beam computed tomography images

The reasons for inaccuracies in alveolar bone measurement from cone-beam computed tomography (CBCT) images might be multifactorial. In this study, we investigated the impact of software, the presence or absence of soft tissues, the voxel size of the scan, and the regions in the jaws on buccal alveolar bone height measurements in pigs at an age equivalent to human adolescents. Marker holes, apical to the maxillary and mandibular molar roots, and mesiodistal molar occlusal reference grooves were created in 6 fresh pig heads (12 for each jaw), followed by CBCT scans at 0.4-mm and 0.2-mm voxel sizes under soft-tissue presence and soft-tissue absence conditions. Subsequently, buccolingual sections bisecting the marker holes were cut, from which the physical alveolar bone height and thickness were measured. One blinded rater, using Dolphin (version 11.5 Premium; Dolphin Imaging, Chatsworth, Calif) and OsiriX (version 3.9; www.osirix-viewer.com) software, independently collected alveolar bone height measurements from the CBCT images. Differences between the CBCT and the physical measurements were calculated. The mean differences and the limit of agreement (LOA, ±1.96 SD) for every jaw, voxel-size, soft-tissue, and software condition were depicted. Each measurement was then assessed for clinical inaccuracy by using 2 levels of criteria (absolute differences between CBCT and physical measurements ≥1 mm, or absolute differences between CBCT and physical measurements ≥0.5 mm), and the interactions between soft-tissue and voxel-size factors for every jaw and software condition were assessed by chi-square tests. Overall, the mean differences between the CBCT and the physical measurements for every jaw, voxel-size, soft-tissue, and software condition were near 0. With all other conditions kept equal, the accuracy of the maxillary CBCT measurements was inferior (larger limit of agreement ranges and higher frequencies of clinical inaccuracy) to the mandibular measurements. The physical thickness of the maxillary alveolar crestal bone was less than 1 mm and significantly thinner than the mandibular counterparts. For every jaw and software condition, the accuracy of measurements from the 0.2-mm soft-tissue presence CBCT images was consistently superior (smaller limit of agreement ranges and lower frequencies of clinical inaccuracy) to those from the 0.4-mm soft-tissue presence, the 0.4-mm soft-tissue absence, and the 0.2-mm soft-tissue absence images; all showed similar accuracies. Qualitatively, the soft-tissue absence images demonstrated much brighter enamel and alveolar bone surface contours than did the soft-tissue presence images. At an adolescent age, the buccal alveolar bone height measured from the maxillary molar region based on 0.4-mm voxel-size CBCT images can have relatively large and frequently inaccurate measurements, possibly due to its thinness. By using 0.2-mm voxel-size scans, measurement accuracy might be improved, but only when the overlying facial and gingival tissues are kept intact.

A comparison of technologies used for estimation of body temperature

Body temperature measurement is an important clinical parameter. The performance of a number of non-invasive thermometers was measured by comparing intra- and inter-operator variability (n = 100) and clinical accuracy (n = 61). Variability was elevated in febrile compared to normothermic subjects for axillary and oral electronic contact thermometer measures and a temporal artery thermometer (p < 0.001 for both). Temporal artery thermometry and one mode of an infrared tympanic thermometer demonstrated significant clinical inaccuracy (p < 0.001 for both). Electronic contact thermometer repeatability and reproducibility are highly variable in febrile adults both in the axilla and oral cavity. Infrared thermometry of the skin over the superficial temporal artery is unreliable for measuring core body temperature, particularly in febrile subjects and patients in theatre. The infrared tympanic thermometers tested are acceptable for clinical practice; however, care should be exercised with the different modes of operation offered.

Patients as Rational Traders: Response to Stewart and DeMarco

Stewart and DeMarco’s economic theory of patient decision-making applied to the case of diabetes is flawed by clinical inaccuracies and an unrealistic depiction of patients as rational traders. The theory incorrectly represents patients’ struggles to optimize their management as calculated trade-offs against the costs of care, and gives an unrealistic, inflexible account of such costs. It imputes to physicians the view that their patients’ lack of compliance is unreasonable, but physicians are accustomed to the variety of human factors which contribute to suboptimal compliance, and work with patients to minimize their influence. By depicting patients as rational traders rather than human beings with a range of motivations and burdens, the economic theory distorts the proper function of informed consent.

Frameless optical computer-aided tracking of a microscope for otorhinology and skull base surgery.

To integrate a digitally controlled operating microscope without a laser autofocus system into a frameless optical computer-aided surgery system and to test the accuracy and usability of this system in otorhinological surgery. Experimental study and case series. Department of Oto-Rhino-Laryngology, Head and Neck Surgery, Inselspital, and the Maurice E. Müller Institute for Biomechanics, University of Bern, Bern, Switzerland. Eight computer-aided microscopic surgical procedures were performed between January and October 2000 on patients with various diseases of the anterior and lateral skull base. The practical accuracy of the navigated microscope on the lateral side of a cadaver skull was 2.27 +/- 0.25 mm and on the anterior side of the same skull was 2.07 +/- 0.35 mm. In all 8 cases of computer-aided microscopic surgery, no complications occurred. Clinical inaccuracy was 2 to 3 mm. Integration of a low-cost, non-laser autofocus microscope into our computer-aided surgery system was successfully performed and offers surgeons the ability to combine the precise optics of the operating microscope with the localization power of a computer-aided system.

Evidence-based management of groin hernia in primary care--a systematic review.

National clinical guidelines on the surgical management of groin hernia have been published by the Royal College of Surgeons of England. There is also a need for guidance on the management of pre- and post-hernia repair patients in primary care, in areas such as diagnosis, referral and advice on recuperation. The purpose of the present study was to determine best practice in primary care aspects of managing groin hernia in adults, by examination of the evidence base. A systematic review of the available evidence was carried out, searching the major electronic databases: Medline, the Cochrane Library, Embase, Assia, Helmis, Cinahl and Psyclit. Key search terms were hern$, inguinal, femoral, groin, truss$, with searches limited to human adult subjects and the English language. Robust research on groin hernia is concerned almost exclusively with the in-patient surgical management of patients undergoing primary elective hernia repair. The areas with which this review was concerned, principally diagnosis, referral and advice about return to work, are areas in which it is more difficult to conduct robustly designed studies. Perhaps because of this, the evidence base on the non-surgical aspects of management is of poor methodological quality, being based primarily on expert opinion, reviews of clinical practice and experience, surveys, descriptive case studies and clinical audits. As the research in this area is generally of poor quality, strong conclusions are precluded, but it is possible to define best practice in some areas of care. In relation to diagnosis, GPs should distinguish correctly between a femoral and inguinal hernia because of the increased risks of strangulation and incarceration associated with the former. Due to clinical inaccuracy, the identification of whether a hernia is direct or indirect is not a good basis on which to base decision making regarding referral for elective repair. The risks associated with surgical repair are those of the normal range found for any procedure. Decisions about the fitness of patients for surgery in this instance are not procedure specific, and therefore the decisions about elective repair especially in older patients should be considered in terms of quality of life and patient choice rather than increased risks with surgical repair. Further research is required to address the gap in the evidence for the management of groin hernia within the primary care sector.

Frameless computer-aided surgery system for revision endoscopic sinus surgery

To increase the intraoperative safety factor and to acquire anatomic assistance during revision endoscopic sinus surgery (RESS), we used an optical computer-aided surgery (CAS) system that we developed collaboratively in Bern, Switzerland. During 1 year, 25 RESSs were performed with CAS: recurrent polyposis (n = 20), recurrent frontal recess stenosis (n = 3), and recurrent frontal recess stenosis with mucocele (n = 2). These patients were compared with a control group of 10 patients undergoing RESS without CAS. The same surgeon (M.C.) performed all operations, and there were no minor or major complications in either group. The clinical inaccuracy of our system is between 0.5 and 2 mm with paired-point and surface matching. The navigation system is an important aid to surgeons in identifying anatomic landmarks that are typically difficult to visualize in this type of surgery, thus reducing the stress placed on the surgeon. (Otolaryngol Head Neck Surg 2000;122:808-13.)

Frameless computer-aided surgery system for revision endoscopic sinus surgery.

To increase the intraoperative safety factor and to acquire anatomic assistance during revision endoscopic sinus surgery (RESS), we used an optical computer-aided surgery (CAS) system that we developed collaboratively in Bern, Switzerland. During 1 year, 25 RESSs were performed with CAS: recurrent polyposis (n = 20), recurrent frontal recess stenosis (n = 3), and recurrent frontal recess stenosis with mucocele (n = 2). These patients were compared with a control group of 10 patients undergoing RESS without CAS. The same surgeon (M.C.) performed all operations, and there were no minor or major complications in either group. The clinical inaccuracy of our system is between 0.5 and 2 mm with paired-point and surface matching. The navigation system is an important aid to surgeons in identifying anatomic landmarks that are typically difficult to visualize in this type of surgery, thus reducing the stress placed on the surgeon.

Obtaining consent for autopsy in dementia research: The Memory and Aging Project experience

Although clinical diagnostic inaccuracy rates in dementia have been reduced in recent years because of increased understanding of dementing disorders, autopsy remains the definitive means for diagnosis of Alzheimer's disease (AD). However, barriers to obtaining autopsy still exist. We report here the voluntary autopsy consent protocol developed by Washington University's Memory and Aging Project. Suggestions by staff and participants over the years have been implemented to develop a protocol that insures a successful autopsy program. From a wallet-sized card of instructions for family reference, to 24-hour availability of staff families and institutions are provided a smooth transition from place of death to autopsy. The rate of voluntary autopsy consent for Memory and Aging Project participants (70 percent) reflects the effectiveness of this program.

Translating Medical Science Into Medical Practice

As medical therapy becomes ever more effective, the need to make the fruits of scientific progress available to all who need them becomes increasingly more urgent. One way is to establish guidelines or standards for provision of services of proven value and to monitor compliance with those recommendations. In their carefully done and provocative study of ambulatory testing in Medicare patients, Weiner et al 1 provide disturbing evidence of a substantial shortfall in the provision of several key diagnostic tests for monitoring patients with diabetes mellitus. See also p 1503. The use of claims data to assess quality of care has been repeatedly criticized, primarily because of its lack of clinical detail and inaccuracies in coding. While these deficiencies limit the usefulness of claims data for evaluating outcomes such as mortality and complications, they are less relevant here because the authors have confined their analysis to the question of whether

The normal Doppler venous examination.

The clinical diagnosis of acute deep vein thrombosis (DVT) is but 50% accurate when compared to the results of contrast venography. This clinical inaccuracy had led to the dependence of the physician upon laboratory diagnosis. Whereas contrast venography is the gold standard of diagnosis, its expense, special equipment, personnel, and discomfort make it unsuitable for evaluating large numbers of patients. For this reason, numerous noninvasive tests utilizing plethysmographic and Doppler techniques have been developed to evaluate patients with suspected venous disease, and when expertly performed have a degree of accuracy of approximately 90%. This degree of accuracy coincides with the experience of our peripheral vascular laboratory using the Doppler venous examination. Based on these statistics, our current practice is to evaluate patients suspected of having DVT with a Doppler venous examination (Figure 1). If the test is abnormal or equivocal, contrast venography is usually obtained and anticoagulation recommended. Contrariwise, if the Doppler venous examination is normal, venography is not obtained, and anticoagulation treatment is not recommended. This practice should reduce the number of venograms in a patient population that is not at an increased risk of pulmonary embolism or repeated deep venous thrombosis. To evaluate the validity and safety of this practice, one hundred eighty-six patients with normal Doppler venous examinations in whom contrast venography was not obtained were evaluated and form the basis of this report.