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Biomedical subjects

S B Tan

Publications and source records attributed to S B Tan.

34 records · Page 2Linked to original sources
PubMed2002

Agreement or prediction: asking and answering the right question.

INTRODUCTION: Measuring agreement and measuring predictive ability are similar but distinct problems. Failure to appreciate the conceptual and practical differences may lead clinical researchers to give the right answer to the wrong question. METHODS: We illustrate the relation and difference between measuring agreement and predictive ability in a non-technical way. We provide a real example investigating the feasibility of using preoperative breast cancer tumour size measurements to estimate postoperative histological size. The intraclass correlation and R-squared are calculated to ascertain the level of agreement and predictive ability respectively. RESULTS: Analysis of agreement and analysis of predictive ability serve different purposes. The optimal solution found in terms of agreement may be different from that found for prediction. CONCLUSIONS: A careful clarification of the goal of an investigation is important. Using an inappropriate analysis can lead to misleading results, or to results that do not really answer the research question of interest.

Anthropometry↗
PubMed2002

Advances in surgical treatment of osteoporotic fractures of the spine.

INTRODUCTION: To highlight recent advances in the management of osteoporotic compression fractures of the spine. METHODS: A MEDLINE search was conducted from January 1975 to October 2001. Keywords included osteoporotic compression fractures, osteoporosis and spine fractures. RESULTS: Osteoporotic fractures of the spine often cause significant morbidity to the elderly individual. Diagnosis requires a detailed history and physical examination and investigations are usually required to exclude other causes of back pain. Magnetic resonance imaging (MRI) is often helpful in excluding other causes of pathologic fracture but may not be confirmatory. Conservative treatment was the traditional approach, but newer percutaneous treatments, such as vertebroplasty and kyphoplasty, are safe and simple day surgery procedures which allow for rapid recovery of symptoms and prevention of increasing spinal deformity. Neurological deficit as a result of spinal canal compromise from retropulsed fragments, though relatively uncommon, is well recognised as a cause of significant morbidity and is a major indication for open spinal surgery. Various spinal approaches including anterior or posterior decompression combined with a variety of stabilisation techniques have been reported in the literature. Rehabilitation is often required to improve physical function. CONCLUSIONS: Osteoporotic fractures of the spine are a common cause of morbidity in the elderly. Patients who have persistent pain despite conservative treatment require investigation to exclude other pathological causes of fracture. Percutaneous vertebroplasty and kyphoplasty are new techniques that offer much promise in the treatment of these elderly patients. Open surgery may still be required where there is significant neurologic compromise.

Aged↗
PubMed2001

The Torg--Pavlov ratio in cervical spondylotic myelopathy: a comparative study between patients with cervical spondylotic myelopathy and a nonspondylotic, nonmyelopathic population.

STUDY DESIGN: A radiologic study to compare the Torg--Pavlov ratios between patients with cervical spondylotic myelopathy and a nonspondylotic, nonmyelopathic population. OBJECTIVES: To determine and compare the Torg--Pavlov ratios between the two groups of patients. SUMMARY OF BACKGROUND DATA: Patients with congenital cervical spinal canal stenosis are more likely to develop cervical spondylotic myelopathy. The Torg--Pavlov ratio eliminates errors related to magnification, a problem with determination of spinal canal stenosis from direct measurements of plain cervical spine radiographs. There has only been one other study that directly compares the Torg--Pavlov ratio between patients with cervical spondylotic myelopathy and a normal control population. METHODS: The preoperative plain lateral cervical spine radiographs of 28 patients with cervical spondylotic myelopathy requiring surgical decompression were compared with radiographs of 88 nonspondylotic, nonmyelopathic patients. The Torg--Pavlov ratio was computed for each level from C3 to C7. RESULTS: The study showed that the Torg--Pavlov ratio is significantly smaller (P < 0.001) in myelopathic patients (mean 0.72 +/- 0.08) compared with the control patients (mean 0.95 +/- 0.14). This was so when individual levels and the mean values were compared. Age was also found to be a significant factor (P = 0.002), although lesser in magnitude when compared with the Torg--Pavlov ratio (P = 0.0001). CONCLUSIONS: The Torg--Pavlov ratio is significantly lower in patients with cervical spondylotic myelopathy compared with a nonspondylotic, nonmyelopathic population. It could possibly be used to predict the likelihood of developing cervical spondylotic myelopathy.

Adolescent↗
PubMed2001

Introduction to Bayesian methods for medical research.

Bayesian statistical methods provide a credible alternative to traditional statistical approaches used in medical research. In this article, the author gives a brief introduction to the key concepts involved in Bayesian methods and compares them with some commonly used non-Bayesian statistical techniques.

Bayes Theorem↗
PubMed2001

The need for collaboration between clinicians and statisticians: some experience and examples.

INTRODUCTION: Very often we see poor communication and collaboration between clinicians and statisticians. Both sides may fail to realise the importance of a truly collaborative effort. In this paper we give examples to illustrate some problems clinicians and statisticians may encounter when they do not have the full support of each other. The aim is to convince both parties the importance of a truly collaborative effort. METHODS: Real examples in various medical research areas are drawn from the authors' practical experience for illustration. The examples cover various research aspects such as the use of computer software, regression analysis and interpretation of findings. RESULTS: Superficial collaboration between clinicians and statisticians may lead to serious problems and sub-optimal research practice that may not be obvious in the first sight. Some of the barriers to effective communication and collaboration are discussed. CONCLUSIONS: On the one hand, robust statistical practice is vital in many medical research projects. On the other hand, medical thinking is important in the formulation and application of statistical strategies. Statistical inputs should be integrated into medical research projects throughout the whole research process. Sporadic contacts between clinicians and statisticians are not enough. Both parties must learn to communicate more effectively and to be willing to collaborate with each other.

Clinical Medicine↗
PubMed2000

Results of cervical laminoplasty and a comparison between single and double trap-door techniques.

Thirty-seven patients were studied for an average of 32.1 months after canal-expansive laminoplasty for the treatment of multiple-level cervical stenosis caused by spondylosis, ossification of posterior longitudinal ligament, prolapsed intervertebral disc, and other conditions. Short-term and medium-term results were recorded clinically, using the scoring system proposed by the Japanese Orthopedic Association. The canal expansion was also recorded with radiological studies. The improvement rate was good to excellent in 58.3% of the patients. Postoperative neurological deterioration occurred in only four patients. Poorer results were observed in female patients and in those in whom surgery was delayed. Surgery within 12 months of onset of symptoms gave good results. Serious complications occurred in only two patients. There were 12 patients who were treated with the single trap-door (unilateral) laminoplasty and 25 patients treated with the double trap-door (sagittal splitting of the spinous processes) laminoplasty; their results were compared. There was no significant difference in neurological outcome between the two methods.

Adult↗
PubMed1999

Endurance training of the trunk extensor muscles in people with subacute low back pain.

BACKGROUND AND PURPOSE: Clinicians treating patients with low back pain often use exercise to reduce pain and improve function. The aim of this study was to evaluate the effectiveness of trunk extensor endurance training in reducing pain and decreasing disability in subjects with subacute low back pain (ie, onset of back pain within 7 days to 7 weeks). SUBJECTS AND METHODS: Patients were randomly assigned to either an experimental group or a control group. A visual analog scale and the pain rating index (PRI) of the McGill Pain Questionnaire (MPQ) were used to obtain baseline measurements of pain. The Roland Morris Disability Questionnaire (RMDQ) was used to measure disability, and the Sorensen Test was used to measure trunk extensor endurance. Subjects in the experimental group attended exercise sessions 3 times a week for 6 weeks. Subjects in the control group did not do exercises. Both groups were given back care advice and hot packs for 15 minutes, 3 to 5 times per week. Reassessments were carried out at 3 and 6 weeks. RESULTS: There were differences between the 2 groups at 3 weeks in regard to pain intensity during the evaluation session and pain experienced over the preceding 24 hours, the total MPQ PRI, the sensory component of the MPQ PRI, and the RMDQ. At 6 weeks, no differences were found for pain measurements, disability scores, and holding time on the Sorensen Test. CONCLUSION AND DISCUSSION: Trunk extensor endurance training reduced pain and improved function at 3 weeks but resulted in no improvement at 6 weeks when compared with the control group. Endurance exercise is considered to expedite the recovery process for patients with an acute episode of low back pain.

Adult↗
PubMed1998

Exploratory thoughts on clinical trials with utilities.

We consider problems of choice of sample size and allocation in the clinical trials context when utilities are explicitly taken into account. In particular, we consider utilities of benefits and side-effects (and their trade-offs), as well as utility functions that trade-off scientific and ethical concerns.

Bayes Theorem↗
PubMed1995

Vascular assessment in the neuropathic diabetic foot.

Diabetic foot infections, a common source of morbidity and mortality, often have been related to vasculopathy and neuropathy in its etiopathogenesis, especially in the elderly person with diabetes. However, blood flow in the neuropathic diabetic foot has not been evaluated extensively, and there is evidence of abnormal blood flow patterns in the neuropathic diabetic foot unrelated to ischemia. The authors studied young persons with diabetes, with varying degrees of neuropathy, to assess the extent of vasculopathy in their lower limbs. Twelve young persons with insulin-dependent (Type I) diabetes (mean age, 36.1 +/- 1.975 years) and peripheral neuropathy, all of whom had previous surgery for diabetic foot infections, were identified. Confirmatory evidence of neuropathy was made using electromyographic studies and clinical tests that showed severe peripheral neuropathy. The results of vascular assessment of both lower limbs did not reveal any change in the pulse wave velocities from the popliteal to the digital vessels of the big toe as compared with correspondingly matched controls. There also was no significant stenosis in any of the vessels studied as far as the level of the dorsalis pedis and posterior tibial vessels. The normal triphasic pattern of arterial blood flow was lost. A monophasic pattern was present in all patients with prolonged diastolic flow at the level of the dorsalis pedis and posterior tibial arteries and distally. The pulsatility index was 3.14 +/- 0.81 as compared with 9.85 +/- 4.2. Mean toe pressures in the patient with diabetes was 64.17 +/- 20.87 mm Hg as compared with 98.23 +/- 10.12 mm Hg in controls. A linear correlation of decreasing toe pressures with increasing severity of neuropathy was seen (R = 0.7). The data suggest that changes exist in the blood flow patterns in young patients with diabetes and neuropathy, even in the absence of lower limb ischemia.

Adult↗
PubMed1994

Effect of operative position on sagittal alignment of the lumbar spine.

A variety of techniques and frames are used for positioning patients during posterior lumbar spinal instrumentation and fusion. Little information is available on the relationship of lumbar lordosis and the various positioning options, so it was felt that further investigation was warranted. Ten volunteers with no history of back pain were positioned and radiographed in the standing position followed by four lateral radiographs with the patient positioned on chest rolls, Andrew's frame, the Hasting's frame, and a four-poster spinal frame. Total lumbar lordosis from L1 to S1 as well as intervertebral body angles at each of the lumbar interspaces using standardized techniques were computed. No significant difference was found in lumbar lordosis between the standing and chest roll position. However, there was approximately a 50% reduction in lumbar lordosis when using the Hasting's, Andrew's, and four-poster frame as compared to the standing and chest roll configuration. The clinical implications are discussed.

Adult↗
PubMed1991

The limitations of magnetic resonance imaging in the diagnosis of pathologic vertebral fractures.

Magnetic resonance imaging has been increasingly used in recent years to screen patients with suspected spinal metastases. The authors present four cases, all of whom were elderly patients with vertebral compression fractures, who were diagnosed with magnetic resonance imaging to have probable neoplastic involvement. In each case, vertebral body biopsies indicated a benign pathology. The authors discuss the diagnostic criteria of magnetic resonance imaging of spinal metastases and the limitations of magnetic resonance imaging in the diagnosis of pathologic vertebral fractures.

Aged↗
PubMed1978

Effects of social disincentive policies on fertility behavior in Singapore.

Five social disincentive policies were implemented by the Singapore government in 1973 to augment its fertility reduction program. The policies involve increasing delivery charges in government hospitals, school admission priority for children, maternity leave, priority in allocation of government housing, and income tax relief. In a two-year prospective study, 1,010 married abortees (study group) and 943 married parturients (comparison group) were questioned to determine their awareness and understanding of these policies, and whether the policies influenced their decision concerning their present pregnancies or would influence future decisions. Except for the tax policy, these disincentives were known to a fairly large proportion of the women studied. Knowledge was positively related to education level. Four of the five disincentives have, to varying degrees, influenced the women's decisions concerning their present pregnancies and may do so in future pregnancies. The two most widely known and most influential disincentives are those affecting school admission priority and accouchement fees.

Demography↗