Risk scoring for time to end-stage knee osteoarthritis: data from the Osteoarthritis Initiative

OBJECTIVE

This study constructs a risk score for patients' progression to end-stage knee osteoarthritis (OA) within 4 years.

DESIGN

The Osteoarthritis Initiative (OAI) was a longitudinal study of the onset and progression of knee OA. Using a recent definition of end-stage knee OA, we implement interval-censored survival forests to select predictors of this endpoint. We fit an interval-censored Cox model for time to end-stage knee OA, using the selected predictors. The risk score is the Cox model's fitted linear combination of the nine selected baseline structural and symptomatic knee OA variables.

RESULTS

We fit our models on a training set of 2,701 patients, and we evaluate on an independent test set of 1,436 patients. On the test sample, we observe a concordance index of 0.86 between risk score and time to end-stage, AUC of 0.87 for predicting end-stage within 24, 36, and 48 months, and positive predictive values that increase with the risk score. This risk stratification algorithm could enrich clinical trial patient enrollment. By enrolling test sample patients with scores above a threshold, a trial could have included 91% of test set patients who reach end-stage within 4 years while only enrolling 45% of the test sample.

CONCLUSION

Using statistical methods, we construct and validate an interpretable risk score for time to end-stage knee OA. This score can help disease-modifying OA treatment developers to select candidates with the highest risk of fast-progressing knee OA.

Protection of rhesus macaques against disease progression from pathogenic SHIV-89.6PD by vaccination with phage-displayed HIV-1 epitopes

The antigenic polymorphism of HIV-1 is a major obstacle in developing an effective vaccine. Accordingly, we screened random peptide libraries (RPLs) displayed on phage with antibodies from HIV-infected individuals and identified an array of HIV-specific epitopes that behave as antigenic mimics of conformational epitopes of gp120 and gp41 proteins. We report that the selected epitopes are shared by a collection of HIV-1 isolates of clades A-F. The phage-borne epitopes are immunogenic in rhesus macaques, where they elicit envelope-specific antibody responses. Upon intravenous challenge with 60 MID50 of pathogenic SHIV-89.6PD, all monkeys became infected; however, in contrast to the naive and mock-immunized monkeys, four of five mimotope-immunized monkeys experienced lower levels of peak viremia, followed by viral set points of undetectable or transient levels of viremia and a mild decline of CD4+ T cells, and were protected from progression to AIDS-like illness. These results provide a new approach to the design of broadly protective HIV-1 vaccines.

Bayesian model selection: analysis of a survival model with a surviving fraction

We describe a methodology for model comparison in a Bayesian framework as applied to survival with a surviving fraction. This is illustrated using a case study of a randomized and controlled clinical trial investigating time until recurrence of depression. Posterior distributions are simulated using Metropolis-within-Gibbs Markov chain methods. Models reflecting the effects of covariates on the log odds of being in the surviving fraction, the log of the hazard rate, as well as both and neither are compared. Bayes factors for comparing the models are obtained by using the bridge sampling method of calculating normalizing constants.

Control of SIV rebound through structured treatment interruptions during early infection

In a randomized controlled trial with acute simian immunodeficiency virus (SIV)-infected macaques, both highly active antiretroviral therapy (HAART) and HAART with fixed-schedule structured treatment interruption (STI-HAART; alternating 3 weeks on and 3 weeks off therapy) suppressed viral load. In the STI-HAART group, T cell virus-specific immune response (VIR) and control of viral rebound increased concurrently during subsequent interruptions. In contrast, VIR did not increase and SIV rebounded after permanent treatment withdrawal in all animals on continuous HAART. Fixed-schedule STI-HAART appears to be an effective alternative to continuous HAART for the early treatment of retroviral infection.

Effect of PMPA and PMEA on the kinetics of viral load in simian immunodeficiency virus-infected macaques

In this study we compared the effect of postexposure treatment of the acyclic nucleoside analogs 9-(2-phosphonylmethoxyethyl)-adenine (PMEA) and 9-(2-phosphonylmethoxypropyl)-adenine (PMPA) on the kinetics of viral load in the blood and lymph nodes of rhesus macaques chronically infected with SIVmac251 for 18 weeks. Two of the four macaques treated with PMPA (20 mg/kg per day) for 28 consecutive days had demonstrable reductions in viral loads of 1.5 and 3 logs. Three of four macaques given the same dosing regimen of PMEA had viral load reductions ranging from 1.25 to 2.8 logs. Furthermore, treatment with either drug caused a reduction in virus burden in the lymph nodes by 2 weeks posttreatment. However, in both PMEA- and PMPA-treated animals, viral loads rebounded to day of treatment levels by 2 weeks after termination of treatment. The extent to which viral load was suppressed was similar for both drugs. In contrast, viral loads in three of four mock-treated animals remained persistently high throughout the study. This study has demonstrated that postexposure treatment with these acyclic nucleoside analogs could modulate the kinetics of viral load reduction in some animals.

Mixture models for eye-tracking data: a case study

Heterogeneity in biomedical data is often a source of great scientific interest and mixture models provide a general framework for modelling the various types that arise in practice. Finite mixture models model discrete subgroups within populations while continuous mixture models inflate the variance to account for over-dispersed data. A potential problem with the application of finite mixture models in practice is that these models may drastically overestimate the number of component densities when there is a lack of model fit. This can have severe consequences, leading the data analyst to attach substantive interpretations to spurious subgroups. For this reason, we propose using the continuous mixture model as an alternative when fitting finite mixture models with an arbitrary number of components. In the context of an example examining a specific oculomotor component of eye-tracking dysfunction in schizophrenia, we demonstrate why the continuous mixture model provides a viable alternative to the finite mixture model for small sample sizes. We present methods for fitting and comparing both models using the parametric bootstrap and EM algorithm, and show that the distinction between the models decreases as the number of component densities in the finite mixture model increases.

Cost utility analysis of maintenance treatment for recurrent depression

This paper presents a cost-utility analysis of three maintenance treatments for recurrent depression: interpersonal therapy (IPT-M), imipramine drug therapy (Drug), and a combination of the two. We base our analysis on the results of the University of Pittsburgh's Controlled Clinical Trial of Maintenance Therapies for Recurrent Depression. We construct a Markovian state-transition model to incorporate clinical effectiveness into cost and quality-of-life impacts; we assign empirical values to the parameters of this model; and we then use Monte Carlo analysis to compare the relative cost effectiveness of the different maintenance treatments. For the patients who met the eligibility standards for the study, Drug maintenance treatment is cost-effective in the strongest sense of the term compared to either a placebo group or IPT-M: it both improves expected lifetime health (measured in quality-adjusted life years, or QALYs) and reduces direct medical costs. This is true even when relatively severe side effects of the drug are considered. Compared to the placebo group, IPT-M and the combination of IPT-M and Drug each improve expected lifetime health, although in neither case are expected direct medical costs reduced. Still, the cost of the resulting health improvements, under $5000/QALY, are very reasonable. A similar conclusion holds comparing Drug and IPT-M to IPT-M alone. All of the above conclusions are quite robust to sensitivity analyses.

Etomidate anesthesia increases seizure duration during ECT. A retrospective study

We reviewed charts of 28 consecutive depressed psychiatric inpatients who had received electroconvulsive therapy (ECT). As a preliminary investigation, we compared the effects of thiopental and etomidate anesthesia on seizure duration. Etomidate, a nonbarbiturate, has been shown to enhance seizure activity in other contexts. The mean age of our sample was 64 years. Because each patient received both etomidate and thiopental at various sessions during their course of ECT, each patient served as his or her own control. The mean proportion of etomidate sessions per patient was 54%. Mean seizure durations were significantly longer (p < 0.001) for the etomidate sessions as compared with the thiopental sessions. In contrast to some prior reports we found that the use of etomidate anesthesia in our sample of 28 consecutive inpatients enhanced seizure duration in ECT. Although controversial, some have advocated that longer seizure times will enhance effectiveness of ECT. We could not compare the anesthetic agents' clinical efficacy in relieving depression due to the retrospective nature of our study.

Preferential infection of CD4+ memory T cells by human immunodeficiency virus type 1: evidence for a role in the selective T-cell functional defects observed in infected individuals

CD4+ T cells of patients with AIDS exhibit a qualitative defect in their ability to respond to soluble antigen while their responses to mitogens remain normal. CD4+ T cells can be broadly divided phenotypically into "naive" [CD45RA+ (2H4+)] and "memory" [CD29+ (4B4+) or CD45RO+ (UCHL1+)] cell subpopulations, which represent distinct maturation stages. To determine the human immunodeficiency virus type 1 (HIV-1) infectability of memory and naive CD4+ T-cell subsets in vitro and to determine the in vivo preference of HIV-1 in these subpopulations, we obtained highly purified CD4+ T-cell subsets from normal and HIV-1-infected individuals and studied them by viral cultivation, quantitative polymerase chain reaction, and functional assays. Polymerase chain reaction studies demonstrated that the memory cell subset of CD4+ T cells is preferentially infected (4- to 10-fold more than naive T cells) by HIV-1 in vitro, and these memory cells are the principal reservoir for HIV-1 within CD4+ T cells obtained from infected individuals. Functional abnormalities attributable to CD4+ T cells in HIV-infected individuals (failure to respond in vitro to soluble antigen or to anti-CD3 monoclonal antibodies) were shown to reside primarily within these memory cells. Thus, the present study suggests that the selective functional defects present in the memory CD4+ T-cell subset of HIV-infected individuals may be a direct result of the preferential infection and consequently greater viral burden within these cells.

Graves' disease: an analysis of thyroid hormone levels and hyperthyroid signs and symptoms

PURPOSE

Assessment of disease severity for patients with hyperthyroidism involves clinical evaluation and laboratory testing. To determine if there is a correlation between symptoms and thyroid function test results, we prospectively studied hyperthyroid patients using a standardized symptom rating scale and serum thyroid function parameters.

PATIENTS AND METHODS

We examined 25 patients with untreated, newly diagnosed Graves' disease using the Hyperthyroid Symptom Scale (HSS) and serum levels of thyroxine (T4), triiodothyronine (T3) relative insulin area (RIA), and estimates of free thyroxine index (FTI). In addition, we compared thyroid hormone levels with standard measures of depression and anxiety in these patients.

RESULTS

When regression analyses controlling for age were performed, none of these symptom ratings were associated with FTI or T3 RIA. The HSS was correlated with goiter size and anxiety ratings and was inversely correlated with age.

CONCLUSION

The present study suggests that there is no relationship between the clinical assessment of disease severity and serum levels of thyroid hormone in untreated Graves' disease.

Psychiatric and neuropsychological response to propranolol in Graves' disease

We describe the endocrine, psychiatric, and neuropsychological assessments of 10 untreated, newly diagnosed Graves' disease subjects who were studied longitudinally at three stages: hyperthyroid (stage 1), after 2 weeks of propranolol treatment (stage 2), and after 6 months of antithyroid treatment (stage 3). Major depression, generalized anxiety disorder, and hypomania were diagnosed at stage 1. Elevations on psychiatric symptom rating scales and in motor activity monitoring at stage 1 were significantly decreased at stage 2 and again at stage 3. Psychiatric improvements paralleled improvements in endocrine symptoms. Neuropsychological improvements were noted on the more challenging memory and attention tasks at stage 3, whereas propranolol treatment was not associated with changes on attention tests. Results are discussed in relation to catecholamine-thyroid hormone interactions, in particular, the beta-adrenergic system.

A symptom rating scale for delirium

The authors present a 10-item clinician-rated symptom rating scale for delirium. Compared to demented, schizophrenic, and normal control groups, 20 delirious subjects scored significantly higher on the scale, which quantitates multiple parameters affected by delirium. The scale can be used alone or in conjunction with an electroencephalogram and bedside cognitive tests to assess the delirious subject.

A psychiatric and neuropsychological study of patients with untreated Graves' disease

We studied 13 untreated Graves' disease subjects in a clinical research unit using endocrine, psychiatric, and neuropsychological assessments. We used SADS interviews, RDC, standardized symptom rating scales, and motor activity monitoring to update earlier studies and quantified psychiatric symptoms to elucidate any correlations between endocrine and psychiatric status. Nine of 13 subjects had major depression, 8/13 had generalized anxiety disorder, and 3/13 were hypomanic. Anxiety levels were much higher than in other hospitalized medical patients. Using a broad battery of neuropsychological testing, we found mild deficits in attention, memory, and complex problem solving that were consistent with previous studies of hyperthyroid patients. The severity of psychiatric symptoms could easily result in an inappropriate referral to a psychiatrist prior to the diagnosis of hyperthyroidism. The relationship between psychiatric symptoms and possible CNS effects of excess levels of thyroid hormone is discussed.

Plasma norepinephrine variations with dietary sodium intake

Plasma catecholamine and renin activity levels were measured across a range of dietary sodium intakes (10--300 mEq/day) in 20 normal male volunteers. Supine plasma norepinephrine levels presented a triphasic pattern in relation to urine sodium, whereas epinephrine levels were not significantly altered by sodium intake, and renin showed the well-known hyperbolic relationship to urine sodium excretion. Highest supine norepinephrine values occurred at low salt intakes, the lowest when sodium excretion was between 100 and 180 mEq/day, and intermediate when sodium excretion was greater than 180 mEq/day. These findings show that sodium intake is an important consideration in the interpretation of plasma norepinephrine levels.