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PubMed1990

A consortium approach to molecular genetic services. Scottish Molecular Genetics Consortium.

The four Scottish university medical genetics centres formed a consortium in 1985 to provide a DNA based service in prenatal diagnosis, carrier detection, and predictive testing for a range of Mendelian disorders. Each centre took sole responsibility for laboratory analyses of an assigned set of disorders, while families continued to be investigated and patients counselled within their own areas. DNA was extracted from relevant tissues in the centre most convenient to the family member and then dispatched to the appropriate laboratory for analysis. Results were interpreted and risks assessed by discussion between laboratory staff and the clinical geneticist in charge of the case. In the first three years of the consortium 92 prenatal diagnoses or exclusion tests were carried out, the majority being for cystic fibrosis (35), Duchenne muscular dystrophy (21), and Huntington's disease (11). Carrier testing was carried out in 271 X linked recessive disorders, the most common indications being Duchenne and Becker muscular dystrophies (198) and haemophilias A and B (48). Predictive testing was attempted in 41 consultants at risk for Huntington's disease, 37 at risk for myotonic dystrophy, and 32 at risk for developing adult polycystic kidney disease. The total of all carrier tests, including those for autosomal recessives, was 543. A consortium or supraregional approach to molecular genetics services has a number of advantages. Constituent laboratories need hold only those probes and enzymes relevant to their assigned disorders and can gain maximum experience with these systems. Scattered families may often be linked into single kinships, thus allowing rapid confirmation of diagnosis when an urgent request is made for a prenatal diagnosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Cystic Fibrosis↗
PubMed1980

Predictive value and efficiency of hematology data.

Laboratory test results and procedures can be evaluated at four levels:1. Analytic analysis of laboratory test: precision, technical sensitivity, technical specificity; 2. Diagnostic analysis of laboratory test: diagnostic sensitivity, diagnostic specificity, Youden index, likelihood ratio, etc.; 3. Operational analysis of laboratory test: predictive value of positive result, predictive value of negative result, efficiency, discriminant function, etc.; 4. Medical decision-making analysis of laboratory test: threshold probability, cost-benefit analysis, solving the decision tree. Analysis of results or selection of tests can occur at any level, without knowledge of the test's evaluation or performance at the remaining levels. Alternatively, the development of new laboratory tests can proceed from level 1 to level 4, or vice versa. Unfortunately, the former is usually the case and most of the tests in use today have never been evaluated at the medical decision-making level (level 4). Recent efforts at developing automated WBC differential counters represent a disproportionate amount of time and energy expended at level 1, and typify our backward approach to laboratory medicine. In thinking about the development of new diagnostic tests, we should begin at level 4 to characterize the properties and specifications that the test must meet. As an example, an in vitro test for the diagnosis of pulmonary embolism could be characterized in this fashion with criteria specified at each of the lower levels. Returning to the question of "How good should a laboratory test be?", we can see that the answer must come from an analysis of the benefit-cost equation (level 4). Figure 2 is a plot of the net benefit and cost of treatment versus the threshold probability. Since the threshold probability defines how certain one must be of the diagnosis before proceeding with treatment, it serves as a minimum probability which should be exceeded by the predictive value of the test. When the benefit--cost ratio is low, a test with a very high predictive value is required to exceed the threshold probability. On the other hand, when the benefit--cost ratio is high, even a test with a low predictive value would be of use to the physician in making the decision to treat the patient. Within this framework, a number of clinical situations could be evaluated and problems requiring the development of highly predictive laboratory tests (low benefit--cost ratios) could be identified. Too much emphasis in laboratory medicine has been placed on the "laboratory" and not enough on the "medicine". How important is the coefficient of variation when the benefit--cost ratio is high? Tests can not be developed or selected appropriately in a therapeutic vacuum.

Adolescent↗
PubMed1995

Neural network prediction of nonstress test results: how often should we perform nonstress tests?

OBJECTIVE: Our purpose was to predict outcomes and optimal intervals for nonstress tests of term gravid women with neural networks. STUDY DESIGN: We studied 100 normal term patients whose 30-minute nonstress tests, performed on 5 consecutive days, were computer analyzed for the following elements: fetal heart rate baseline, variability, signal loss, accelerations (> 15 beats/min), and decelerations. The training set used 65 patients; the testing, 35 patients. Nonstress test data (days 1 to 4) were inputs; day 5 data were training patterns. Networks for each nonstress test element used Brainmaker Macintosh 1.0 (California Scientific Software, Nevada City, Calif.) trained to 0.12 tolerance. Actual fetal heart rate elements and their daily differences were compared with predictions by the networks and multiple regressions. RESULTS: There was little difference between networks using daily or alternate-day inputs for predicting test performance on day 5; networks using test intervals > 2 days could not be trained to tolerance. Long-term fetal heart rate variation was the nonstress test element best predicted. Daily differences networks provided better prediction of all day 5 data than did actual daily values networks or multiple regression formulas. CONCLUSIONS: Baseline long-term fetal heart rate variability seems to be the most predictable fetal heart rate element over time and should merit more consideration in overall fetal testing. Fetal heart rate elements are not easily predicted by any method for intervals longer than 2 days. Using longer test intervals might run a greater risk for unanticipated changes in nonstress test outcomes, even when fetal condition is normal.

Female↗
PubMed2001

Using a roster and haplotyping is useful in risk assessment for persons with intermediate and reduced penetrance alleles in Huntington disease.

The risk of a person having a child with an inherited disorder, caused by an unstable triplet repeat, such as Huntington disease (HD), depends on the expansion of the mutation in that person, which is connected both to the biological nature of the mutation and to the person's relation to the carrier of the full mutation. Once the mutation causing HD was identified, we were able to diagnose sporadic patients. A sporadic patient can sometimes be connected to a known HD pedigree by using a roster. By haplotyping and calculating the posterior identity-by-descent probability, we could establish whether a connection was coincidental or not. Furthermore, we describe the frequency of intermediate and reduced penetrance alleles detected. Using the family history and the roster to search for a connection, we examined whether these alleles were on the HD haplotype of a family. It is important to know the origin of an intermediate or reduced penetrance allele because if it comes from an HD branch of the family or from the non-HD affected side of the pedigree, different risks for relatives and penetrance ensue. In our study, most intermediate alleles came from the non-HD-affected side of the pedigree and had a repeat size in the lower range with a negligible risk for expansion. Intermediate alleles on the HD haplotypes were larger and found in predictive test applicants from known families or relatives from new mutations with a higher risk for expansion. Reduced penetrance alleles in the higher range were mainly found in symptomatic and predictive test applicants from known families, with a considerable risk for penetrance, although at older age. We conclude that a roster, a thorough family history, and haplotyping in persons with intermediate and reduced penetrance alleles are essential in considering the risk of a person having (a child with) HD.

Age of Onset↗
PubMed1998

A comparison of in vitro tests for predicting the severity of haemolytic disease of the fetus and newborn.

Haemolytic disease of the newborn (HDN) is characterized by the presence of IgG antibodies in the maternal circulation which cause haemolysis in the fetus by crossing the placenta and sensitizing red cells for destruction by macrophages in the fetal spleen. Numerous serological, quantitative and cellular assays have been developed to predict the severity of HDN. These assays all measure and/or characterize alloantibodies in the maternal circulation. Quantitative assays which accurately measure antibody levels correlate with disease severity better than serological assays which are inherently less precise. Nevertheless, high antibody levels are found in some cases of mild HDN and relatively low antibody levels are found in some severe cases. This suggests that disease severity is influenced by factors in addition to antibody concentration. These factors remain to be fully elucidated but may include the subclass and glycosylation of maternal antibodies, the structure, site density, maturational development and tissue distribution of blood group antigens, the efficiency of IgG transport to the fetus, the functional maturity of the fetal spleen, polymorphisms which affect Fc receptor function, and the presence of HLA-related inhibitory antibodies. Cellular assays which are sensitive to factors affecting antibody function have therefore been developed in an attempt to improve the prediction of disease severity. Although these assays are cumbersome, there are now sufficient data to suggest that some cellular assays, when used as part of a structured approach to diagnostic testing, may provide clinically-useful information to complement serological and quantitative assays.

Adult↗
PubMedDate not supplied

Clinical limitations of neuropsychological testing in predicting treatment outcome among alcoholics.

The purpose of the present study was to investigate a number of factors that may influence the relationship between neuropsychological impairment and treatment outcome among alcoholics. Cognitive deficit upon admission to treatment was significantly related to the individual's age but independent of the years of problem drinking and the recency of the last drink prior to assessment. Significant improvement was noted on measures of neuropsychological function over the period from treatment admission to 6-month follow-up assessment. On the average, improvement in functioning occurred across time despite drinking relapses during the intervening period. The individual's age, but not years of problem drinking, was associated with recovery of function; neither of these variables interacted with subsequent drinking status to affect differentially the changes in cognitive functioning. Finally, selected measures of neuropsychological function assessed both at admission and 6-month follow-up were reliably related to follow-up employment status but unrelated to the average amount of alcohol consumed per day and to the number of heavy drinking days during the 3-month period between the 6- and 9-month follow-ups. The results are discussed in terms of the need for determining the utility of neuropsychological measures in predicting everyday functioning among alcoholics and for selecting domains of assessment other than cognitive status to predict treatment outcome.

Alcohol Drinking↗
PubMed1996

Apolipoprotein E and Alzheimer's disease. A rapidly expanding field with medical and epidemiological consequences.

The Alzheimer's Association and the National Institute on Aging sponsored a meeting of experts in Alzheimer's disease (AD), geneticists, social scientists, and ethicists in Chicago in October 1995 to discuss the use of apolipoprotein E (APOE) genotyping in Alzheimer's disease. A short scientific report was published in the scientific journal Lancet with recommendations from the group. Several areas were discussed, including: (1) the scientific basis for recommendations on the application and uses of APOE genotyping, (2) clarifying the clinical and epidemiological research that needs to done, (3) genetic counseling issues, (4) ethical and legal issues, and (5) potential uses of APOE genotyping for treatment care planning. This contribution was a general introduction to begin the meeting. The genetic association of APOE genotypes with the age of onset distribution and risk of Alzheimer's disease was reviewed. An analysis of the current applications for three distinctly different applications of APOE genotyping was presented with the following conclusions: (1) predictive testing for cognitively intact persons was not recommended; (2) APOE genotyping is a promising adjunct for use in the differential diagnosis of patients with dementia; and (3) APOE genotyping may have a use in selecting therapies; however, further prospective studies are necessary. There is no universal "APOE test for AD." A strong emphasis was made to avoid use of the term in making recommendations regarding APOE genotyping without specific reference to the type of application involved. The predictive testing of asymptomatic persons versus APOE genotyping as a diagnostic adjunct for symptomatic patients has been seriously confused in both the lay and clinical press. The former application is not recommended, but diagnostic usefulness early in clinical evaluations for dementia has been confirmed.

Age of Onset↗
PubMed2005

Defining response in clinical trials for obsessive-compulsive disorder: a signal detection analysis of the Yale-Brown obsessive compulsive scale.

OBJECTIVE: Many studies of the treatment of obsessive-compulsive disorder (OCD) have used percent reduction cutoffs on the Yale-Brown Obsessive Compulsive Scale (YBOCS) to classify patients as treatment responders. However, reduction criteria have varied from 20% to 50%, with studies of cognitive-behavioral therapy (CBT) using a more stringent criterion than studies of pharmacotherapy. The aim of this retrospective investigation was to determine optimal YBOCS reduction criteria for classifying patients as responders. METHOD: Data from 87 adult clinic and research outpatients meeting DSM-IV-TR criteria for OCD according to structured interview were examined, comparing the percent YBOCS reduction from pretreatment to posttreatment with 2 "gold standard" criteria from the Clinical Global Impressions (CGI) scale: much or very much improved and mild illness or better. Signal detection analyses were used to determine the sensitivity, specificity, predictive value of a positive test, predictive value of a negative test, and efficiency of various YBOCS reduction cutoffs. RESULTS: A YBOCS reduction cutoff of 30% was optimal for predicting improvement on the CGI. The 20% cutoff used by many pharmacologic studies resulted in a high number of false positives, whereas the 50% cutoff used by most CBT studies resulted in a high number of false negatives. For predicting mild illness or better at posttreatment, a YBOCS reduction cutoff of 40% to 50% was optimal. CONCLUSIONS: A YBOCS reduction criterion of 30% appears to be optimal for determining clinical improvement, whereas a 40% to 50% reduction criterion is appropriate for predicting mild illness at posttreatment. Future studies should employ a standard definition of treatment response in order to facilitate cross-study comparisons.

Adult↗
PubMed2005

Haemodynamic indices of the early phase of the tilt test: does measurement predict outcome?

INTRODUCTION: Tilt testing (TT) is a well-established tool in the diagnosis of syncope. However, it is time-consuming. Therefore, identification of parameters that could shorten the duration of TT is desirable. AIM: To identify and assess the usefulness of early haemodynamic parameter changes in prediction of the tilt test results in a group of patients with syncope of unknown aetiology. METHODS: The study involved a group of 105 patients, including 61 women and 44 men, with a mean age of 34.2+/-13.7 (from 13 to 82) years, with at least two episodes of syncope in the last 6 months. The head-up tilt test was carried out according to protocol 60/20 min and if necessary was continued after administration of sublingual nitroglycerine in a dose of 250 g. The assessment of haemodynamic indices was performed employing the beat-to-beat method using the Portapres M2 device. Systolic (SBP) and diastolic (DBP) arterial pressure, heart rate (HR), cardiac output (CO) and stroke volume (SV), and total peripheral vascular resistance (TPR) were analysed. The measured values of haemodynamic indices were calculated by means of averaging 10-second intervals within 3-minute studied periods either before or after tilting a patient. Mean baroreceptor sensitivity (BRS) for the same 3-minute-long intervals was evaluated using the xBRS (cross-correlation) method. In the analysis, differences (Rx) of the haemodynamic values between the beginning of tilting a patient and the rest period were also calculated. RESULTS: Loss of consciousness was noted in 47 (46%) of the studied patients - group I. The remaining subjects (58 patients, 54%) did not develop syncope during TT (group II). The univariate and multivariate logistic analyses of regression revealed that the mean vascular resistance difference (meanRTPR) <-10 dyn.s/cm8 was an independent risk factor of syncope (chi2=3.4; p<0.0008). The presence of this risk factor was associated with a significantly higher risk of a positive response during the tilt test (65% vs 39%; RR: 1.7, 95% CI: 1.2-3.2). In predicting a positive TT result, sensitivity of this parameter was 65%, specificity was 61% and the prognostic value of the positive and negative result was 32% and 86%, respectively. CONCLUSIONS: In patients with syncope of unknown origin, an early (within first 3 minutes of TT) asymptomatic fall in total peripheral vascular resistance is a significant predictor of a positive final result of the test.

Adolescent↗