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PubMed1992

Reduced anti-Mycobacterium tuberculosis antibody response in tuberculosis patients with acquired immunodeficiency syndrome.

1. When the sera of patients with tuberculosis were tested for anti-Mycobacterium tuberculosis IgG using an indirect ELISA, the test was positive for 94.1% of the samples from patients not having AIDS (N = 51), but for only 37.5% of the samples from patients with AIDS (N = 16). 2. False-positive results were obtained for 7.3% of patients not infected with HIV (N = 96) and for 4.7% of patients infected with HIV (N = 64). 3. In most serum samples obtained from patients with tuberculosis and AIDS after the beginning of specific treatment there was a reduction of the ELISA absorbance at 490 nm with time. 4. These results indicate that serological tests for the detection of anti-M. tuberculosis IgG in patients with AIDS are of limited value for the diagnosis of tuberculosis, most likely as a consequence of the underlying immune defect of the patients.

AIDS-Related Opportunistic Infections↗
PubMed1992

Maternal serum screening for Down's syndrome: the effect of routine ultrasound scan determination of gestational age and adjustment for maternal weight.

OBJECTIVE: To investigate the effect of using a routine ultrasound estimate of gestational age and maternal weight adjustment on maternal serum alpha-fetoprotein (AFP), unconjugated oestriol (uE3) and human chorionic gonadotrophin (hCG) levels in antenatal screening for Down's syndrome. DESIGN: Women with a singleton pregnancy without Down's syndrome were screened using the three serum markers and an estimate of gestational age based on 'dates' (time since first day of the last menstrual period) and one based on an ultrasound scan examination was recorded together with maternal weight. SETTING: Women attending the Homerton Hospital, Hackney, for their antenatal care between February 1989 and January 1990. SUBJECTS: 2113 women with a singleton pregnancy without Down's syndrome. RESULTS: The use of ultrasound to estimate gestational age (usually based on the biparietal diameter of the fetal skull) led to a significant reduction in the variance of each marker at a given week of pregnancy. The level of each marker was negatively associated with maternal weight, so that adjustment for weight also led to a reduction in variance. These data on gestational age and maternal weight, taken together with published data on pregnancies associated with Down's syndrome, indicate that the routine use of ultrasound to estimate gestational age will increase the detection rate from 58% to 67% while maintaining the false-positive rate at 5%, or reduce the false-positive rate from 5.7% to 3.1% while maintaining the detection rate at 60%. Routine maternal weight adjustment for the serum marker levels was much less useful, increasing the detection rate by about 0.5% for a given false-positive rate, or reducing the false-positive rate about 0.1% for a given detection rate. CONCLUSION: An ultrasound gestational age estimate available at the time of Down's syndrome screening confers a substantial advantage to screening performance with a further small benefit resulting from maternal weight adjustment, which is worth adopting if it can be done without difficulty or extra cost.

Biomarkers↗
PubMed1990

Statistical considerations in cancer screening programs.

The goal of cancer screening is the early detection and treatment of disease, with a consequent reduction in the mortality rate. Evaluation of whether a particular screening program can achieve this goal is a difficult task. Two components of the screening process must be assessed. The first is the ability of the screening test to detect cancer early while minimizing the number of false-positive results. In this regard, the specificity of the test ordinarily must be very high, approaching 99%. No screening test for prostate cancer has yet been reported to have a specificity this high, indicating that any prostate cancer screening program using currently available tests will have to deal with the problem of a large number of false-positive findings. To evaluate the overall impact of a screening program, the best procedure is the randomized controlled trial with cancer-specific mortality as the endpoint. This endpoint is used because it avoids the lead time and length biases inherent in other outcome variables such as stage shift and case survival. The screening randomized controlled trial must be carefully planned and implemented, because it is lengthier and more costly than the usual therapy trial because of differences in study populations, trial design relative to the planned population intervention, and the extent of knowledge of disease natural history. A further important component of screening evaluation is cost. The decision to implement or continue a screening program can be aided by using cost-effectiveness analysis, which bases a decision on the ranking of cost-to-benefit ratios for the various programs contending for limited funds. Screening cost includes the cost of the test, the cost of side effects of the test, and the costs of biopsy and treatment, while screening benefit can be measured in terms of lives saved, life years saved, or quality-adjusted life years.

Cost-Benefit Analysis↗
PubMed1992

Maternal serum unconjugated oestriol and human chorionic gonadotrophin levels in pregnancies with insulin-dependent diabetes: implications for screening for Down's syndrome.

OBJECTIVE: To investigate maternal serum unconjugated oestriol (uE3) and human chorionic gonadotrophin (hCG) levels in pregnant women with insulin-dependent diabetes mellitus and to consider the implications of the results for antenatal screening for Down's syndrome. DESIGN: Descriptive study using stored antenatal serum samples. SETTING: Stored serum samples collected from women receiving routine antenatal care in Oxford. SUBJECTS: 126 singleton pregnancies in 92 women with insulin-dependent diabetes mellitus and for each pregnancy, two pregnancies without diabetes matched for gestational age and duration of storage of the serum sample. None of the pregnancies was associated with fetal neural tube defect or Down's syndrome. MAIN STUDY MEASURES: Maternal serum uE3 and hCG levels at 15-22 weeks gestation. Alpha-fetoprotein (AFP) levels were also measured for comparison. RESULTS: The median uE3 level in the diabetic pregnancies was 0.92 multiples of the median (MoM) for pregnancies without diabetes at the same gestational age (P less than 0.05); and the hCG level was 0.95 MoM (P = 0.48). The median AFP level was also reduced to 0.77 MoM (P less than 0.001). CONCLUSION: The reduction in uE3 and AFP levels in insulin-dependent diabetic pregnancies is sufficiently great to be taken into account in maternal serum screening programmes for Down's syndrome. Dividing the uE3 and AFP levels in such pregnancies by the corresponding median for insulin-dependent diabetic pregnancies will yield a similar false-positive rate in pregnancies with and without insulin-dependent diabetes mellitus.

Chorionic Gonadotropin↗
PubMed1976

Myocsrdial uptake of technetium-99m stannous pyrophosphate following direct current transthoracic countershock.

The effect of direct current (DC) countershock upon myocardial technetium-99m stannous pyrophosphate (PYP) uptake was studied in 22 dogs. All eight dogs imaged had positive abnormal PYP scintigrams that were usually indistinguishable from experimental infarction. In three animals, additional areas of radionuclide uptake were seen in overlying noncardiac tissue. Left and right ventricular myocardial PYP uptake averaged (+/- SEM) 23 +/- 5 times control and 24 +/- 6 times control, respectively. These activity ratios occurred without reduction in regional myocardial blood flow (RMBF), and were associated with histologic evidence of necrosis. The necrosis was usually epicardial, corresponding to the transmural site of greatest PYP uptake. The magnitude of PYP accumulation and the weight of damaged tissue increased with increasing applied energy. Thus, PYP uptake following DC countershock could result in false-positive interpretation of acute ischemic myocardial infarction. Since RMBF is normal in regions of PYP uptake, the major determinant of radionuclide accumulation is the extent of cellular damage.

Animals↗
PubMed1992

Automated interictal EEG spike detection using artificial neural networks.

Feed-forward, error-back-propagation artificial neural networks were applied to recognition of epileptiform patterns in the EEG. The inherent network properties of generalization and variability tolerance were effective in identifying wave forms that differed from the training patterns but still maintained 'epileptiform' spatio-temporal characteristics. The certainty of recognition was measured as a continuous function with a range of 0-1. Two levels of certainty (0.825 and 0.900) were used to indicate recognition of spikes and sharp waves (SSW). An average 94.2% (+/- 7.3) of the SSW were recognized; 20.9% (+/- 22.9) of all recognized SSW were false-positive recognitions. The time required for pattern recognition was well within the time required for digitizing the analogue data. This study provides evidence that neural network technology is, in principle, an effective pattern recognition strategy for identification of epileptiform transients in the EEG. The analysis is sufficiently rapid to be of potential value as a strategy for data reduction of long recordings stored on bulk media.

Electroencephalography↗
PubMed1992

Reporting and interpreting adjuvant therapy clinical trials. International Breast Cancer Study Group (formerly Ludwig Group).

Identifying effective adjuvant treatments for patients with node-negative breast cancer is made difficult by the heterogeneity of the disease, the relatively low event rate and long follow-up time required, and the small magnitude of effects of current therapies. Several aspects of clinical trials that influence the appropriate reporting and interpretation of statistical results are discussed. We point out that the P value is a measure of the statistical uncertainty of an observed outcome and depends on the number of events available for analysis; it is not a measure of the magnitude of a treatment effect. We recommend that the relative reduction in the risk of an event and its 95% confidence interval be presented as an estimate of the treatment effect size, and that absolute improvements be used to judge whether treatment benefits outweigh the costs for the patient population. We suggest that subgroup analyses are important to define treatment effects within groups with different prognoses, and should be used with the understanding that multiple comparisons increase the chance of a false-positive result. Subgroup analysis should rely on the estimates of relative treatment effect and should avoid the use of the P value to declare incorrectly that "treatment is effective for one subgroup but not for another." We present the meta-analysis (overview) as a powerful method to demonstrate the statistical significance of a modest treatment effect by increasing the number of events available for analysis. The interpretation of overviews should consider the potential for treatment interactions and the validity of indirect comparisons that are not protected by a randomized design.(ABSTRACT TRUNCATED AT 250 WORDS)

Breast Neoplasms↗
PubMed1977

Peripheral pulmonary wedge angiography in chronic obstructive pulmonary disease. Relationship to pulmonary function, chest x-ray film, and hemodynamic data.

Peripheral pulmonary wedge angiographic studies can investigate only limited areas of the pulmonary vascular bed; nevertheless, this technique is very useful in emphasizing the morphologic changes of small vessels (less than 1 mm in diameter) in pulmonary emphysema. The aim of this work is to determine the relationship between peripheral wedge angiographic appearances and pulmonary function, the chest x-ray film, and hemodynamic data in patients with chronic obstructive pulmonary disease. Three healthy subjects, four patients with type-A chronic obstructive pulmonary disease, and eight patients with type-B chronic obstructive pulmonary disease were studied. Among the tests of pulmonary function, only a marked reduction (less than 60 percent of predicted) of the diffusing capacity for carbon monoxide is always indicative of severe widespread emphysema. No relationship was found between hemodynamic data and peripheral wedge angiographic findings. Some agreement resulted between the chest x-ray film and peripheral wedge angiographic abnormalities only in patients with type-A chronic obstructive pulmonary disease; on the contrary, in patients with type-B chronic obstructive pulmonary disease, both false-positives and false-negatives were noted.

Angiography↗
PubMed1976

The spirographic "kink". A sign of emphysema.

The significance of the "kink" occurring in the early portion of the forced expiratory spirogram of some patients with obstructed airflow was investigated in 153 patients with chronic obstructive pulmonary disease or asthma. The kink, which is presumably due to airway collapse, is facilitated by the presence of emphysema, which results in loss of elastic recoil, a positive pleural pressure, high bronchiolar resistance, and structural weakness in the walls of the major airways. A significant reduction of carbon-monoxide diffusing capacity was used as the indicator of the presence of significant anatomic emphysema. Eighty percent (39) of 49 patients with the spirographic kink had a low diffusing capacity, whereas only 16 of those without the kink had significantly impaired diffusion. Seventy percent (39) of the 56 patients who had emphysema by this criterion demonstrated a spirographic kink. This test is, therefore, offered as a simple, effective, and widely applicable screening procedure for detecting emphysema, with a low incidence of false-positive results.

Asthma↗
PubMed1975

An appraisal of the nitroblue tetrazolium reduction test.

The available literature on the nitroblue tetrazolium reduction test is reviewed. The mechanism of this test is poorly understood. There are two basic methods of performing the test, namely, the stimulated and the spontaneous methods. However, the test procedure has not been standardized, and numerous modifications have ensued resulting in a number of technics. The stimulated test has proved to be valuable for screening patients or carriers with chronic granulomatous disease of childhood. It is one of the useful tests in studying neutrophil dysfunction. On the other hand, extensive accumulated data indicate that this test, be it stimulted or spontaneous, cannot be relied upon as an absolute test to differentiate bacterial from nonbacterial infectious disease as there have been numerous false-positive and false-negative results. When this test is used, the result should be interpreted in the context of other laboratory test results and the clinical picture of the patient. Preliminary data indicate that in certain diseases, if the initial test is positive in a particular patient, it may be useful as one of the follow-up tests to ascertain the activity of the disease process.

Bacterial Infections↗
PubMed1975

Role of 67gallium citrate scanning in the management of non-Hodgkin's lymphoma.

67Gallium scans were performed as part of the initial evaluation in 45 patients with non-Hodgkin's lymphoma. Eighteen of these patients underwent staging laparotomy and splenectomy. In addition, scans were performed either shortly after therapy was completed or during subsequent followup in 10 patients. The initial scans were found most useful for patients with histiocytic lymphoma: in detecting sites of involvement above the diaphragm and the high para-aortic/mesenteric region, and when tumors were greater than 2 cm in diameter. The addition of 67Ga scanning to the pre-operative clinical evaluation reduced the number of incorrectly staged patients from 8 to 4. Reversion of previously positive 67Ga scans to negative in 3 patients with suspected persistent or recurrent disease was associated with fibrosis and no lymphoma when biopsied. Five other patients had histologically documented positive 67Ga scans post-therapy; in 1 the 67Ga scan was only definitive noninvasive procedure. Despite the occurrence of both false-positive and false-negative 67Ga scans, this procedure appears to be a useful supplement to the pretreatment evaluation of patients with non-Hodgkin's lymphoma, especially the histiocytic form. Confirmation of its ability to detect high para-aortic/mesentric involvement may subsequently result in a reduction of the number of staging laparotomies necessary. For the post-treatment followup of these patients 67Ga scans may prove to be valuable noninvasive investigation.

Abdominal Neoplasms↗
PubMed1990

The redox-cycling assay is not suited for the detection of pyrroloquinoline quinone in biological samples.

Based on the results of the so-called redox-cycling assay it has been claimed that various common foods and beverages as well as mammalian body fluids and tissues contain substantial quantities (microM) of free PQQ [M. Paz et al. (1989) in: PQQ and Quinoproteins (J.A. Jongejan and J.A. Duine, eds.) Kluwer Academic Publishers, Dordrecht, pp. 131-143 and J. Killgore et al. (1989) Science 245, 850-852]. However, by investigating samples from such sources with a biological assay of nM sensitivity, we could not confirm these claims. Analysis of the samples with procedures that proved adequate for the detection of PQQ adducts and conjugates gave equally negative results. To account for the positive response in the redox-cycling assay, as opposed to the negative results obtained by other methods, a search was made for those substances in these samples that caused the false-positive reactions. It was found that a number of commonly occurring biochemicals like ascorbic and dehydroascorbic acid, riboflavin and to a lesser extent pyridoxal phosphate, gave a positive response in the redox-cycling assay. The amounts of these interfering substances that were determined in the samples by independent methods could well explain the response. In separate experiments it was found that the effect of PQQ added to biological samples was obscured over an appreciable range of concentrations. For these reasons it must be concluded that the redox-cycling assay is not suited for the detection of PQQ in these samples. Any claims that are based on the results of this method should be disregarded.

Animals↗
PubMed1990

Successful use of pooled sera to determine HIV-1 seroprevalence in Zaire with development of cost-efficiency models.

To determine the accuracy and cost efficiency of pooling sera prior to HIV-1 testing, sera from 8,000 Kinshasa factory workers and their spouses were screened individually (2.44% seropositive) and in 800 pools of 10 sera each. There were no false-negative or false-positive pools, resulting in a calculated seroprevalence estimate of 2.42%. Further testing of all sera in positive pools can identify HIV-positive individuals. These applications were modeled to compare the cost-efficiency of pooling with individual testing under different conditions. The results suggest that pooling provides an alternative test format for use in both developing and industrialized countries when the seroprevalence and/or the marginal cost of obtaining a sample are sufficiently low. For our cohort, testing only the pools for seroprevalence estimation resulted in a 78% cost saving compared with individual testing; pooling with subsequent identification of individual seropositives represented a 56% cost reduction.

Acquired Immunodeficiency Syndrome↗
PubMedDate not supplied

A clinic-based system for monitoring the quality of techniques for the diagnosis of gonorrhea.

The author describes a clinic-based system that monitors the quality of techniques for diagnosis of gonorrhea by continuous comparison of the results of gram-strained smears of urethral and cervical specimens with the corresponding cultures. Discrepant results are immediately reviewed. During a two-year period, the system detected two defects in culture incubation, visual defects in a laboratory technician, and three unexplained reductions in cultural sensitivity. The system motivates clinicians and laboratory technicians to maintain a high level of quality control. In 11,474 comparisons of urethral smear and culture results, there was agreement in 96.9% while the smear alone was positive in 1.6% and the culture alone in 1.5%. Review of positive-smear-negative-culture discrepancies indicated that most smears judged "false-positive" were so classified on the basis of false-negative cultures. In study of 1,331 women, the endocervical smeras identified 60% (273/455) of those with positive culture discrepancies. Many of these may have represented false-negative cultures.

Clinical Laboratory Techniques↗
PubMed1979

Results of ophthalmosonometry and supraorbital photoplethysmography in evaluating carotid arterial stenoses.

A total of 263 patients underwent either periorbital ophthalmosonometry (Doppler ultrasound) or a combination of ophthalmosonometry and supraorbital photoplethysmography (SOPPG) to determine the presence or absence of a hemodynamically significant lesion (occlusion or greater than 50% reduction in lumen diameter). There were 522 vessels studied with Doppler ultrasound and 272 vessels with a combination of the two modalities. The tests were correlated with carotid arteriography to determine their accuracy. Overall accuracy of the Doppler ultrasound examination was 95%. A normal Doppler ultrasound examination was obtained in 367 vessels and arteriography confirmed the absence of a hemodynamically significant lesion in 93%. Of 155 vessels with an abnormal Doppler examination, 149 (96%) were proven on arteriography to have hemodynamically significant lesions. The Doppler ultrasound examination had a high incidence of false-negative examinations (26%) in those vessels that were between 50% and 99% stenotic, however. The SOPPG alone had a high incidence of false-positive examinations (19%); however, in 155 vessels with a normal SOPPG, 98% were proved to have no hemodynamically significant lesion. The combination of Doppler ultrasound and SOPPG was highly accurate in identifying patients with hemodynamically significant lesions. Of 97 vessels with such lesions, 96 (99%) had either an abnormal Doppler ultrasound examination or an abnormal SOPPG. In 240 vessels with concordant results of the Doppler ultrasound and SOPPG, the presence or absence of a hemodynamically significant lesion was accurately predicted in 235 (98%).

Arterial Occlusive Diseases↗
PubMed1975

Evaluation of the usefulness of nitroblue tetrazolium reduction test (NBT test) for detection of bacterial infection in cancer patients.

False positivity of the NBT test in neoplastic diseases described by some authose may be a limitation in the use of the test for infection screening in cancer patients. For explaining this problem studies were performed in a group of 30 patients with various untreated malignancies without infection and in 20 of these with bacteriologically confirmed infections. The obtained results were compared with those in groups of normal persons without and with infection. Slightly modified Park method for spontaneous and stimulated NBT test was used. No significant differences between patients of both groups without infection were found. The increase in positivity of the test in presence of infection was lower in cancer patients than in normal subjects, however, it was non-significant. We did not observe any false-positive results in our patients, though one case of false negativity in myeloma is described separately. It is concluded that neoplastic disease does not cause, as such positivity of the NBT test. Because of similar response of NBT test to presence of infection, the NBT test is recognized as very useful for infection screening in cancer patients similarly as in normal persons.

Adult↗
PubMed1992

[Echographic measuring of the length of the fetal femur in the screening for Down syndrome].

OBJECTIVE: Our purpose was to assess the value of sonographic measurement of fetal femur length in the second trimester, as a screening tool for Down's syndrome. STUDY DESIGN: We evaluated a consecutive series of fetuses scanned by a single sonologist at the time of amniocentesis between 15 and 19 weeks. The study group consisted of fetuses with Down's syndrome (N = 16); the control group comprised normal fetuses (N = 1163). A linear regression model of the normal femur length based on biparietal diameter (BPD), was established for our population; the ratios of measured to expected femur length for a viven BPD (FL M/E) were calculated in the two groups. To test statistical significance of observed differences between case and control population, unpaired t test was used. The ability of specific FL M/E cut-off values to discriminate between Down syndrome and normal fetuses was assessed by Fisher's exact test. RESULTS: The mean ratio of measured to expected femur length was significantly lower in the Down syndrome as compared with control population (0.9473, DS 0.0795) versus 1.0, DS 0.0745) (p < 0.0045). The ratio of 0.91 or less predicted Down's syndrome with a sensitivity of 43.7% and a false-positive rate of 8.6%. For women with risk of one in 250 and one in 1000 of having an affected fetus based on maternal age, a shortened femur yielded positive predictive values of one in 26 and one in 105, respectively. CONCLUSION: These results suggest that the sonographic measurement of fetal femur length for the screening of Down syndrome in the low-risk population is hindered by a high false positive rate (about 9%). It follows that the percentage of women requiring an amniocentesis would increase to un unacceptably high level. The utilization of this biometric marker may be helpful, in our opinion, for identifying fetuses at risk for Down syndrome in women between 35 and 38 years of age. These women in fact, are not offered amniocentesis for the prenatal diagnosis of Down's syndrome in the majority of italian institutions. The sonographic measurement of fetal femur length could detect about 45% of fetal Down's syndrome, offering an amniocentesis to 9% of women, with a consequent reduction of the cost required. Only a prospective study can evaluate the efficacy of this method to predict Down syndrome in such group of women.

Adult↗
PubMed1990

[Measuring temporal transmission properties of the visual system. Diagnostic value in suspected optic nerve neuritis].

The temporal transfer properties of the visual system were examined in 157 patients with suspected acute optic neuritis or papillitis. Foveal modulation sensitivity was measured as a function of temporal frequency (DeLange curve) both for the affected eye and the unaffected fellow eye. Patients with acute optic neuritis typically show a reduction of foveal modulation sensitivity at all temporal frequencies, high temporal frequencies above 10 cps being more markedly affected. The aim of the present study was to determine the sensitivity and specificity of this simple psychophysical procedure for the diagnosis of neuritis or papillitis in a reasonably large population of patients with suspected acute optic neuritis or papillitis. In each case the final diagnosis was confirmed by evaluation of the clinical signs and symptoms, the course of disease and additional diagnostic procedures, e.g. electrophysiology, perimetry, neurological examination including CT, lumbal puncture and examination of cerebrospinal fluid. In 136 cases (86.6%) the result read from the DeLange curve was correctly positive or negative. In 17 cases (10.8%) the DeLange curve indicated a false-positive and in 4 cases (2.6%), a false-negative result.

Flicker Fusion↗