The impact of improved detection and treatment of isoniazid resistant tuberculosis on prevalence of multi-drug resistant tuberculosis: A modelling study

Introduction

Isoniazid-resistant, rifampin susceptible tuberculosis (INHR-TB) is the most common form of drug resistant TB globally. Treatment of INHR-TB with standard first-line therapy is associated with high rates of multidrug resistant TB (MDR-TB). We modelled the potential impact of INHR-TB detection and appropriate treatment on MDR-TB prevalence.

Methods

A decision analysis model was developed to compare three different strategies for the detection of TB (AFB smear, Xpert MTB/RIF, and Line-Probe Assays (LPA)), combined with appropriate treatment. The population evaluated were patients with a globally representative prevalence of newly diagnosed, drug-susceptible (88.6%), isoniazid-resistant (7.3%), and multidrug resistant (4.1%) pulmonary TB. Our primary outcome was the proportion of patients with MDR-TB after initial attempt at diagnosis and treatment within a 2-year period. Secondary outcomes were the proportion of i) individuals with detected TB who acquired MDR-TB ii) individuals who died after initial attempt at diagnosis and treatment.

Results

After initial attempt at diagnosis and treatment, LPA combined with appropriate INHR-TB therapy resulted in a lower proportion of prevalent MDR-TB (1.61%; 95% Uncertainty Range (UR: 2.5^th and 97.5^th percentiles generated from 10 000 Monte Carlo simulation trials) 1.61–1.65), when compared to Xpert (1.84%; 95% UR 1.82–1.85) and AFB smear (3.21%; 95% UR 3.19–3.26). LPA also resulted in fewer cases of acquired MDR-TB in those with detected TB (0.35%; 95% UR 0.34–0.35), when compared to Xpert (0.67%; 95% UR 0.65–0.67) and AFB smear (0.68%; 95% UR 0.67–0.69). The majority of acquired MDR-TB arose from the treatment of INHR-TB in all strategies. Xpert-based strategies resulted in a lower proportion of death (2.89%; 95% UR 2.87–2.90) compared to LPA (2.93%; 95% UR 2.91–2.94) and AFB smear (3.21%; 95% UR 3.19–3.23).

Conclusion

Accurate diagnosis and tailored treatment of INHR-TB with LPA led to an almost 50% relative decrease in acquired MDR-TB when compared with an Xpert MTB/RIF strategy. Continued reliance on diagnostic and treatment protocols that ignore INHR-TB will likely result in further generation of MDR-TB.

Predicting tuberculosis relapse in patients treated with the standard 6-month regimen: an individual patient data meta-analysis

BACKGROUND

Relapse continues to place significant burden on patients and tuberculosis (TB) programmes worldwide. We aimed to determine clinical and microbiological factors associated with relapse in patients treated with the WHO standard 6-month regimen and then evaluate the accuracy of each factor at predicting an outcome of relapse.

METHODS

A systematic review was performed to identify randomised controlled trials reporting treatment outcomes on patients receiving the standard regimen. Authors were contacted and invited to share patient-level data (IPD). A one-step IPD meta-analysis, using random intercept logistic regression models and receiver operating characteristic curves, was performed to evaluate the predictive performance of variables of interest.

RESULTS

Individual patient data were obtained from 3 of the 12 identified studies. Of the 1189 patients with confirmed pulmonary TB who completed therapy, 67 (5.6%) relapsed. In multipredictor analysis, the presence of baseline cavitary disease with positive smear at 2 months was associated with an increased odds of relapse (OR 2.3(95% CI 1.3 to 4.2)) and a relapse risk of 10%. When area under the curve for each multipredictor model was compared, discrimination between low-risk and higher-risk patients was modest and similar to that of the reference model which accounted for age, sex and HIV status.

CONCLUSION

Despite its poor predictive value, our results indicate that the combined presence of cavitary disease and 2-month positive smear status may be the best currently available marker for identifying individuals at an increased risk of relapse, particularly in resource-limited setting. Further investigation is required to assess whether this combined factor can be used to indicate different treatment requirements in clinical practice.

Screening for Latent Tuberculosis Infection in Migrants With CKD: A Cost-effectiveness Analysis

RATIONALE & OBJECTIVE

In countries with a low tuberculosis (TB) incidence, TB disproportionately affects populations born abroad. TB persists in these populations through reactivation of latent TB infection (LTBI) acquired before immigration. Those with chronic kidney disease (CKD) are at increased risk for reactivation and may benefit from LTBI screening and treatment.

STUDY DESIGN

Health administrative data from British Columbia, Canada, were used to inform a cost-effectiveness analysis evaluating LTBI screening in those diagnosed with stage 4 or 5 CKD not requiring dialysis (late-stage CKD) and those who began dialysis therapy.

SETTING & POPULATION

Permanent residents establishing residency in British Columbia, Canada, between 1985 and 2012 who had late-stage CKD diagnosed or began dialysis therapy.

INTERVENTIONS

Screening with the tuberculin skin test or interferon-gamma release assay (IGRA) compared to no LTBI screening at the time of late-stage CKD diagnosis and time of dialysis therapy initiation. Treatment for those who tested positive was isoniazid for 9 months.

OUTCOMES

Costs (2016 Can $), TB cases, and quality-adjusted life-years (QALYs). The incremental cost-effectiveness ratio for QALYs gained was calculated.

MODEL, PERSPECTIVE, & TIMEFRAME

Discrete event simulation model using a health care system perspective, 1.5% discount rate, and 5-year time horizon.

RESULTS

Screening with IGRA was superior to the tuberculin skin test in all situations. Screening with IGRA was less expensive and resulted in better outcomes compared to no screening in those initiating dialysis therapy from countries with an elevated TB incidence. In individuals with late-stage CKD, screening with IGRA was only cost-effective in those 60 years or older (cost per QALY gained, <$48,000) from countries with an elevated TB incidence.

LIMITATIONS

This study has limitations in generalizability to different epidemiologic settings and in modeling complicated clinical decisions.

CONCLUSIONS

LTBI screening should be considered in non-Canadian-born residents initiating dialysis therapy and those with late stage CKD who are older.

Introduction of spirometry into clinical practice in Georgetown, Guyana: quality and diagnostic outcomes

SETTING

Georgetown Public Hospital Corporation (GPHC), a 600-bed publicly funded referral hospital in Georgetown, Guyana.

OBJECTIVE

To assess spirometry quality and diagnostic outcomes 2 years after the introduction of spirometry into routine clinical practice at GPHC.

DESIGN

We performed a retrospective review of 476 consecutive spirometry assessments performed from November 2013 to November 2015. We assessed the proportion and trend of spirometry tests meeting acceptability criteria, along with diagnostic interpretations and spirometry laboratory referral patterns.

RESULTS

Overall, 80.4% of the 454 initial spirometry measurements on unique patients met the acceptability criteria, with no significant change in the proportion of acceptable spirometry over the study period (P = 0.450). Of the 369 (81.3%) first tests considered interpretable, 139 (30.6%) were normal, 151 (33.3%) were obstructive, 54 (11.9%) were suggestive of a restrictive pattern, 25 (5.5%) were suggestive of a mixed disorder and 119 (26.2%) tests met the definition of reversibility.

CONCLUSION

Over a 2-year period, high-quality spirometry was performed in GPHC, a publicly funded hospital in a middle-income country with no pre-existing specialised respiratory service.

The effect of text messaging on latent tuberculosis treatment adherence: a randomised controlled trial

There is limited high-quality evidence available to inform the use of text messaging to improve latent tuberculosis infection (LTBI) treatment adherence.We performed a parallel, randomised controlled trial at two sites to assess the effect of a two-way short message service on LTBI adherence. We enrolled adults initiating LTBI therapy from June 2012 to September 2015 in British Columbia, Canada. Participants were randomised in a 1:1 ratio to standard LTBI treatment (control) or standard LTBI treatment plus two-way weekly text messaging (intervention). The primary outcome was treatment completion, defined as taking ≥80% prescribed doses within 12 months (isoniazid) or 6 months (rifampin) of enrolment. The trial was unblinded except for the data analyst.A total of 358 participants were assigned to the intervention (n=170) and control (n=188) arms. In intention-to-treat analysis, the proportion of participants completing LTBI therapy in the intervention and control arms was 79.4% and 81.9%, respectively (RR 0.97, 95% CI 0.88-1.07; p=0.550). Results were similar for pre-specified secondary end-points, including time-to-completion of LTBI therapy, completion of >90% of prescribed LTBI doses and health-related quality of life.Weekly two-way text messaging did not improve LTBI completion rates compared to standard LTBI care; however, completion rates were high in both treatment arms.

Continuous Electronic Fetal Monitoring during Labor: A Critique and a Reply to Contemporary Proponents

A half century after continuous electronic fetal monitoring (EFM) became the omnipresent standard of care for the vast majority of labors in the developed countries, and the cornerstone for cerebral palsy litigation, EFM advocates still do not have any scientific evidence justifying EFM use in most labors or courtrooms. Yet, these EFM proponents continue rationalizing the procedure with a rhetorical fog of meaningless words, misleading statistics, archaic concepts, and a complete disregard for medical ethics. This article illustrates the current state of affairs by providing an evidence-based review penetrating the rhetorical fog of a prototypical EFM advocate.

Chronometric Evidence for Central Postponement in Temporally Overlapping Tasks

When the stimuli from two tasks arrive in rapid succession (the overlapping tasks paradigm), response delays are typically observed. Two general types of models have been proposed to account for these delays. Postponement models suppose that processing stages in the second task are delayed due to a single-channel bottleneck. Capacity-sharing models suppose that processing on both tasks occurs at reduced rates because of sharing of common resources. Postponement models make strong and distinctive predictions for the behaviour of variables slowing particular second-task stages, when assessed in single- and dual-task conditions. In Experiment 1, subjects were required to make manual classification responses to a tone (S1) and a letter (S2), presented at stimulus onset asynchronies of 50, 100, and 400 msec, making R1 responses to S1 as promptly as possible. The second response, R2, but not R1, was delayed in the dual task condition, and the effects of two S2 variables (degradation and repetition) on R2 response times in dual- and single-task conditions closely matched the predictions of a postponement model with a processing bottleneck at the decision/response-selection stage. In Experiment 2, subjects were encouraged to emit both responses close together in time. Use of this response grouping procedure had little effect on the magnitude of R2 response times, or on the pattern of stimulus factor effects on R2, supporting the hypothesis that the same underlying postponement process was operating. R1 response times were, however, dramatically delayed, and were now affected by S2 difficulty variables. The results provide strong support for postponement models of dual-task interference in the overlapping tasks paradigm, even when response times are delayed on both tasks.

A half century of electronic fetal monitoring and bioethics: silence speaks louder than words

Bioethics abolished the prevailing Hippocratic tenet instructing physicians to make treatment decisions, replacing it with autonomy through informed consent. Informed consent allows the patient to choose treatment after options are explained by the physician. The appearance of bioethics in 1970 coincided with the introduction of electronic fetal monitoring (EFM), which evolved to become the fetal surveillance modality of choice for virtually all women in labor. Autonomy rapidly pervaded all medical procedures, but there was a clear exemption for EFM. Even today, EFM remains immune to the doctrine of informed consent despite continually mounting evidence which proves the procedure is nothing more than myth, illusion and junk science that subjects mothers and babies alike to increased risks of morbidity and mortality. And ethicists have remained utterly silent through a half century of EFM misuse. Our article explores this egregious ethical failure by reviewing EFM's lack of clinical efficacy, discussing the EFM related harm to mothers and babies, and focusing on the reasons that this obstetrical procedure eluded the revolutionary change from the Hippocratic tradition to autonomy through informed consent.

Cost-effectiveness of post-landing latent tuberculosis infection control strategies in new migrants to Canada

BACKGROUND

The majority of tuberculosis in migrants to Canada occurs due to reactivation of latent TB infection. Risk of tuberculosis in those with latent tuberculosis infection can be significantly reduced with treatment. Presently, only 2.4% of new migrants are flagged for post-landing surveillance, which may include latent tuberculosis infection screening; no other migrants receive routine latent tuberculosis infection screening. To aid in reducing the tuberculosis burden in new migrants to Canada, we determined the cost-effectiveness of using different latent tuberculosis infection interventions in migrants under post-arrival surveillance and in all new migrants.

METHODS

A discrete event simulation model was developed that focused on a Canadian permanent resident cohort after arrival in Canada, utilizing a ten-year time horizon, healthcare system perspective, and 1.5% discount rate. Latent tuberculosis infection interventions were evaluated in the population under surveillance (N = 6100) and the total cohort (N = 260,600). In all evaluations, six different screening and treatment combinations were compared to the base case of tuberculin skin test screening followed by isoniazid treatment only in the population under surveillance. Quality adjusted life years, incident tuberculosis cases, and costs were recorded for each intervention and incremental cost-effectiveness ratios were calculated in relation to the base case.

RESULTS

In the population under surveillance (N = 6100), using an interferon-gamma release assay followed by rifampin was dominant compared to the base case, preventing 4.90 cases of tuberculosis, a 4.9% reduction, adding 4.0 quality adjusted life years, and saving $353,013 over the ensuing ten-years. Latent tuberculosis infection screening in the total population (N = 260,600) was not cost-effective when compared to the base case, however could potentially prevent 21.8% of incident tuberculosis cases.

CONCLUSIONS

Screening new migrants under surveillance with an interferon-gamma release assay and treating with rifampin is cost saving, but will not significantly impact TB incidence. Universal latent tuberculosis infection screening and treatment is cost-prohibitive. Research into using risk factors to target screening post-landing may provide alternate solutions.

Burden of non-adherence to latent tuberculosis infection drug therapy and the potential cost-effectiveness of adherence interventions in Canada: a simulation study

OBJECTIVE

Pharmaceutical treatment of latent tuberculosis infection (LTBI) reduces the risk of progression to active tuberculosis (TB); however, poor adherence tempers the protective effect. We aimed to estimate the health burden of non-adherence, the maximum allowable cost of hypothetical new adherence interventions to be cost-effective and the potential value of existing adherence interventions for patients with low-risk LTBI in Canada.

DESIGN

A microsimulation model of LTBI progression over 25 years.

SETTING

General practice in Canada.

PARTICIPANTS

Individuals with LTBI who are initiating drug therapy.

INTERVENTIONS

A hypothetical intervention with a range of effectiveness was evaluated. Existing drug adherence interventions including peer support, two-way text messaging support, enhanced adherence counselling and adherence incentives were also evaluated.

PRIMARY AND SECONDARY OUTCOME MEASURES

Simulation outcomes included healthcare costs, TB incidence, TB deaths and quality-adjusted life years (QALYs). Base case results were interpreted against a willingness-to-pay threshold of $C50 000/QALY.

RESULTS

Compared with current adherence levels, full adherence to LTBI drug therapy could reduce new TB cases from 90.3 cases per 100 000 person-years to 35.9 cases per 100 000 person-years and reduce TB-related deaths from 7.9 deaths per 100 000 person-years to 3.1 deaths per 100 000 person-years. An intervention that increases relative adherence by 40% would bring the population near full adherence to drug therapy and could have a maximum allowable annual cost of approximately $C450 per person to be cost-effective. Based on estimates of effect sizes and costs of existing adherence interventions, we found that they yielded between 900 and 2400 additional QALYs per million people, reduced TB deaths by 5%-25% and were likely to be cost-effective over 25 years.

CONCLUSION

Full adherence could reduce the number of future TB cases by nearly 60%, offsetting TB-related costs and health burden. Several existing interventions are could be cost-effective to help achieve this goal.

Treatment outcomes for isoniazid-resistant tuberculosis under program conditions in British Columbia, Canada

Background

Every year, over 1 million people develop isoniazid (INH) resistant tuberculosis (TB). Yet, the optimal treatment regimen remains unclear. Given increasing prevalence, the clinical efficacy of regimens used by physicians is of interest. This study aims to examine treatment outcomes of INH resistant TB patients, treated under programmatic conditions in British Columbia, Canada.

Methods

Medical charts were retrospectively reviewed for cases of culture-confirmed INH mono-resistant TB reported to the BC Centre for Disease Control (BCCDC) from 2002 to 2014. Treatment regimens, patient and strain characteristics, and clinical outcomes were analysed.

Results

One hundred sixty five cases of INH mono-resistant TB were included in analysis and over 30 different treatment regimens were prescribed. Median treatment duration was 10.5 months (IQR 9–12 months) and treatment was extended beyond 12 months for 26 patients (15.8%). Fifty six patients (22.6%) experienced an adverse event that resulted in a drug regimen modification. Overall, 140 patients (84.8%) had a successful treatment outcome while 12 (7.2%) had an unsuccessful treatment outcome of failure (n = 2; 1.2%), relapse (n = 4; 2.4%) or all cause mortality (n = 6; 3.6%).

Conclusion

Our treatment outcomes, while consistent with findings reported from other studies in high resource settings, raise concerns about current recommendations for INH resistant TB treatment. Only a small proportion of patients completed the recommended treatment regimens. High quality studies to confirm the effectiveness of standardized regimens are urgently needed, with special consideration given to trials utilizing fluoroquinolones.

A syndemic approach to assess the effect of substance use and social disparities on the evolution of HIV/HCV infections in British Columbia

BACKGROUND

Co-occurrence of social conditions and infections may affect HIV/HCV disease risk and progression. We examined the changes in relationship of these social conditions and infections on HIV and hepatitis C virus (HCV) infections over time in British Columbia during 1990-2013.

METHODS

The BC Hepatitis Testers Cohort (BC-HTC) includes ~1.5 million individuals tested for HIV or HCV, or reported as a case of HCV, HIV, HBV, or tuberculosis linked to administrative healthcare databases. We classified HCV and HIV infection status into five combinations: HIV-/HCV-, HIV+monoinfected, HIV-/HCV+seroconverters, HIV-/HCV+prevalent, and HIV+/HCV+.

RESULTS

Of 1.37 million eligible individuals, 4.1% were HIV-/HCV+prevalent, 0.5% HIV+monoinfected, 0.3% HIV+/HCV+ co-infected and 0.5% HIV-/HCV+seroconverters. Overall, HIV+monoinfected individuals lived in urban areas (92%), had low injection drug use (IDU) (4%), problematic alcohol use (4%) and were materially more privileged than other groups. HIV+/HCV+ co-infected and HIV-/HCV+seroconverters were materially most deprived (37%, 32%), had higher IDU (28%, 49%), problematic alcohol use (14%, 17%) and major mental illnesses (12%, 21%). IDU, opioid substitution therapy, and material deprivation increased in HIV-/HCV+seroconverters over time. In multivariable multinomial regression models, over time, the odds of IDU declined among HIV-/HCV+prevalent and HIV+monoinfected individuals but not in HIV-/HCV+seroconverters. Declines in odds of problematic alcohol use were observed in HIV-/HCV+seroconverters and coinfected individuals over time.

CONCLUSIONS

These results highlight need for designing prevention, care and support services for HIV and HCV infected populations based on the evolving syndemics of infections and social conditions which vary across groups.

The Ethics of Teaching Physicians Electronic Fetal Monitoring: And Now for the Rest of the Story

Electronic fetal monitoring (EFM) does not predict or prevent cerebral palsy (CP), but this myth remains entrenched in medical training and practice. The continued use of this ineffectual diagnostic modality increases the cesarean section rate with concomitant harms to mothers and babies alike. EFM, as it is used in defensive medical practice, is a violation of patient autonomy and raises serious ethical concerns. This review addresses the need for improved graduate medical education so that physicians and medical residents are taught both sides of the EFM-CP story.

Predicting tuberculosis risk in the foreign-born population of British Columbia, Canada: study protocol for a retrospective population-based cohort study

INTRODUCTION

Improved understanding of risk factors for developing active tuberculosis (TB) will better inform decisions about diagnostic testing and treatment for latent TB infection (LTBI) in migrant populations in low-incidence regions. We aim to examine TB risk factors among the foreign-born population in British Columbia (BC), Canada, and to create and validate a clinically relevant multivariate risk score to predict active TB.

METHODS AND ANALYSIS

This retrospective population-based cohort study will include all foreign-born individuals who acquired permanent resident status in Canada between 1 January 1985 and 31 December 2013 and acquired healthcare coverage in BC at any point during this period. Multiple administrative databases and disease registries will be linked, including a National Immigration Database, BC Provincial Health Insurance Registration, physician billings, hospitalisations, drugs dispensed from community pharmacies, vital statistics, HIV testing and notifications, cancer, chronic kidney disease and dialysis treatment, and all TB and LTBI testing and treatment data in BC. Extended proportional hazards regression will be used to estimate risk factors for TB and to create a prognostic TB risk score.

ETHICS AND DISSEMINATION

Ethical approval for this study has been obtained from the University of British Columbia Clinical Ethics Review Board. Once completed, study findings will be presented at conferences and published in peer-reviewed journals. An online TB risk score calculator will also be created.

Neurological Fallacies Leading to Malpractice: A Case Studies Approach

A young woman presents with an intracranial arachnoid cyst. Another is diagnosed with migraine headache. An elderly man awakens with a stroke. And a baby delivered vaginally after 2 hours of questionable electronic fetal monitoring patterns grows up to have cerebral palsy. These seemingly disparate cases share a common underlying theme: medical myths. Myths that may lead not only to misdiagnosis and treatment harms but to seemingly never-ending medical malpractice lawsuits, potentially culminating in a settlement or judgment against an unsuspecting neurologist. This article provides a case studies approach exposing the fallacies and highlighting proper management of these common neurologic presentations.

Patient Partnerships Transforming Sleep Medicine Research and Clinical Care: Perspectives from the Sleep Apnea Patient-Centered Outcomes Network

ABSTRACT

Due to an ongoing recent evolution in practice, sleep medicine as a discipline has been compelled to respond to the converging pressures to reduce costs, improve outcomes, and demonstrate value. Patient "researchers" are uniquely placed to participate in initiatives that address the specific needs and priorities of patients and facilitate the identification of interventions with high likelihood of acceptance by the "customer." To date, however, the "patient voice" largely has been lacking in processes affecting relevant policies and practice guidelines. In this Special Report, patient and research leaders of the Sleep Apnea Patient-Centered Outcomes Network (SAPCON), a national collaborative group of patients, researchers and clinicians working together to promote patient-centered comparative effectiveness research, discuss these interrelated challenges in the context of sleep apnea, and the role patients and patient-centered networks may play in informing evidence-based research designed to meet patient's needs. We first briefly discuss the challenges facing sleep medicine associated with costs, outcomes, and value. We then discuss the key role patients and patient-centered networks can play in efforts to design research to guide better sleep health care, and national support for such initiatives. Finally, we summarize some of the challenges in moving to a new paradigm of patient-researcher-clinician partnerships. By forging strong partnerships among patients, clinicians and researchers, networks such as SAPCON can serve as a living demonstration of how to achieve value in health care.

Attentional Limitations in Doing Two Tasks at Once

People generally have difficulty doing two tasks at once. To explain this fact, theorists have proposed that central processing—the thought-like stages following perceptual encoding and preceding response processing—takes place for only one task at a time. Because this bottleneck imposes severe limits on human cognitive processes, research has attempted to find exceptions. There is now solid evidence that, at least in the laboratory, the entire bottleneck can be completely bypassed under favorable combinations of circumstances. While these findings provide a ray of hope for enabling parallel multitasking in real-world scenarios, it will not be easy to take advantage of the combination of conditions that appear to be necessary.

Declaring a tuberculosis outbreak over with genomic epidemiology

We report an updated method for inferring the time at which an infectious disease was transmitted between persons from a time-labelled pathogen genome phylogeny. We applied the method to 48 Mycobacterium tuberculosis genomes as part of a real-time public health outbreak investigation, demonstrating that although active tuberculosis (TB) cases were diagnosed through 2013, no transmission events took place beyond mid-2012. Subsequent cases were the result of progression from latent TB infection to active disease, and not recent transmission. This evolutionary genomic approach was used to declare the outbreak over in January 2015.

Tuberculosis and chronic kidney disease: an emerging global syndemic

The link between chronic kidney disease (CKD) and tuberculosis (TB) has been known for more than 40 years, but the interaction between these 2 diseases is still poorly understood. Dialysis and renal transplant patients appear to be at a higher risk of TB, in part related to immunosuppression along with socioeconomic, demographic, and comorbid factors. Meanwhile, TB screening and diagnostic test performance is suboptimal in the CKD population, and there is limited evidence to guide protocols. Given the increasing prevalence of CKD in TB endemic areas, a merging of CKD and TB epidemics could have significant public health implications, especially in low- to middle-income countries such as India and China, that are experiencing rapid increases in CKD prevalence and account for more than one-third of global TB prevalence. To begin addressing TB-CKD, a clear understanding of the relationship between these 2 conditions needs to be established, and consistent, evidence-based screening and treatment guidelines need to be developed.

Chronometric Evidence for two Types of Attention

Parallel processing in the human brain is subject to severe attentional limits, but it is unclear whether such limits arise from a single attentional process or multiple distinct attentional processes We provide new evidence that two candidates, input attention and central attention, operate at different temporal stages of processing This conclusion is supported by chronometric analyses showing that the same reference stage (letter identification) operates after the stage at which input attention operates, but prior to the stage at which central attention operates The finding that attention operates at different temporal loci provides new support for the existence of distinct attentional processes