Chlamydial and Gonococcal Infections and Adverse Reproductive Health Conditions Among Patients Assigned Female at Birth in the Veterans Health Administration

BACKGROUND

Reproductive age female individuals comprise the fastest-growing segment of Veterans Health Administration patients, but little is known about rates of reproductive health outcomes among those with chlamydia or gonorrhea infections. Our aim was to estimate the risk of pelvic inflammatory disease, ectopic pregnancy, infertility, and pelvic pain in female veterans tested for chlamydia or gonorrhea.

METHODS

We performed a retrospective cohort analysis of female veterans tested for chlamydia or gonorrhea between January 1, 2010, and December 31, 2020. We calculated rates of pelvic inflammatory disease, ectopic pregnancy, infertility, and pelvic pain per 100,000 person-years and used Cox proportional hazards regression models to estimate the risk of these reproductive health conditions according to infection status after adjustment for age, race, ethnicity, military sexual trauma, mental health diagnoses, and substance use disorder.

RESULTS

Of female veterans, 232,614 were tested at least once for chlamydia or gonorrhea, with a total of 1,665,786 person-years of follow-up. Of these, 12,971 had positive chlamydia or gonorrhea results (5.8%, 796 cases per 100,000 person-years). Compared with people who tested negative, those testing positive had double the risk of pelvic inflammatory disease (adjusted hazard ratio [aHR], 1.94; 95% confidence interval [CI], 1.81-2.07), 11% increased risk of infertility (aHR, 1.11; 95% CI, 1.04-1.18), 12% increased risk of pelvic pain (aHR, 1.12; 95% CI, 1.08-1.17), and 21% increased risk of any of these conditions (aHR, 1.21; 95% CI, 1.17-1.25). People with positive chlamydia or gonorrhea testing tended to have an increased risk of ectopic pregnancy (aHR, 1.14; 95% CI, 1.0-1.30). Among those with a positive test result, 2218 people (17.1%) had 1 or more additional positive test results. Compared with those with 1 positive test result, people with more than 1 positive test result had a significantly increased risk of pelvic inflammatory disease (aHR, 1.37; 95% CI, 1.18-1.58), infertility (aHR, 1.20; 95% CI, 1.04-1.39), and pelvic pain (aHR1.16; 95% CI, 1.05-1.28), but not ectopic pregnancy (aHR, 1.09; 95% CI, 0.80-1.47).

CONCLUSIONS

Female veterans with positive chlamydia or gonorrhea results experience a significantly higher risk of pelvic inflammatory disease, infertility, and pelvic pain, especially among those with repeat infection.

Success of the US Veterans Health Administration's Hepatitis C Virus Care Continuum in the Direct-acting Antiviral Era

BACKGROUND

Estimated hepatitis C prevalence within the Veterans Health Administration is higher than the general population and is a risk factor for advanced liver disease and subsequent complications. We describe the hepatitis C care continuum within the Veterans Health Administration January 1, 2014-December 31, 2022.

METHODS

We included individuals in Veterans Health Administration care 2021-2022 who were eligible for direct-acting antiviral treatment January 1, 2014-December 31, 2022. We evaluated the proportion of Veterans who progressed through each step of the hepatitis C care continuum, and identified factors associated with initiating direct-acting antivirals, achieving sustained virologic response, and repeat hepatitis C viremia.

RESULTS

We identified 133,732 Veterans with hepatitis C viremia. Hepatitis C treatment was initiated in 107,134 (80.1%), with sustained virologic response achieved in 98,136 (91.6%). In those who achieved sustained virologic response, 1,097 (1.1%) had repeat viremia and 579 (52.8%) were retreated for hepatitis C. Veterans of younger ages were less likely to initiate treatment and achieve sustained virologic response, and more likely to have repeat viremia. Stimulant use and unstable housing were negatively associated with each step of the hepatitis C care continuum.

CONCLUSIONS

The Veterans Health Administration has treated 80% of Veterans with hepatitis C in care 2021-2022 and achieved sustained virologic response in more than 90% of those treated. Repeat viremia is rare and is associated with younger age, unstable housing, opioid use, and stimulant use. Ongoing efforts are needed to reach younger Veterans, and Veterans with unstable housing or substance use disorders.

Testing and Case Rates of Gonorrhea, Chlamydia, Syphilis, and HIV among People with Substance Use Disorders in the Veterans Health Administration

BACKGROUND

Little is known about national patterns of sexually transmitted infection (STI) testing and infections among people with substance use disorders (SUDs).

METHODS

This study used a national retrospective analysis of people with SUDs receiving healthcare in the Veterans Health Administration in 2019 (N = 485,869). We describe testing rates, test positivity, and case rates for gonorrhea, chlamydia, syphilis, and HIV among individuals with alcohol, opioid, cocaine, and noncocaine stimulant use disorders in a national cohort of Veterans Health Administration patients.

RESULTS

Test and case rates for all STIs were highest among people with noncocaine stimulant use. People with alcohol use disorder had the lowest testing rates but intermediate incidence for all STIs. People with multiple SUDs had higher incidence of all STIs than those with single SUDs. Mental health diagnoses and houselessness were common. The HIV test positivity was 0.14% to 0.36% across SUD groups.

CONCLUSIONS

Sexually transmitted infection testing rates between SUD groups were discordant with their respective case rates. High STI rates in people with SUDs suggest a need for more comprehensive testing, particularly for those with noncocaine stimulant use and those with comorbid houselessness or mental health diagnoses.

Sexually Transmitted Infection Testing in the National Veterans Health Administration Patient Cohort During the Coronavirus Disease 2019 Pandemic

Background

We performed a retrospective study of chlamydia, gonorrhea, syphilis, and human immunodeficiency virus (HIV) testing in the Veterans Health Administration (VHA) during 2019-2021.

Methods

We determined the annual number of chlamydia, gonorrhea, syphilis, and HIV tests from 2019 through 2021 using electronic health record data. We calculated rates by age, birth sex, race, census region, rurality, HIV status, and use of preexposure prophylaxis.

Results

The VHA system experienced a 24% drop in chlamydia/gonorrhea testing, a 25% drop in syphilis testing, and a 29% drop in HIV testing in 2020 versus 2019. By the conclusion of 2021, testing rates had recovered to 90% of baseline for chlamydia/gonorrhea, 91% for syphilis, and 88% for HIV. Declines and subsequent improvements in sexually transmitted infection (STI) testing occurred unequally across age, sex, race, and geographic groups. Testing for all 4 STIs in 2021 remained below baseline in rural Veterans. Excluding those aged <25 years, women experienced a steeper decline and slower recovery in chlamydia/gonorrhea testing relative to men, but quicker recovery in HIV testing. Asian Americans and Hawaiian/Pacific Islanders had a steeper decline and a slower recovery in testing for chlamydia/gonorrhea. Black and White Veterans had slower recovery in HIV testing compared with other race groups. People living with HIV experienced a smaller drop in testing for syphilis compared with people without HIV, followed by a near-total recovery of testing by 2021.

Conclusions

After dramatic reductions from 2019 to 2020, STI testing rates returned to near-baseline in 2021. Testing recovery lagged in rural, female, Asian American, Hawaiian/Pacific Islander, and Black Veterans.

Discussion and Initiation of HIV Pre-exposure Prophylaxis Were Rare Following Diagnoses of Sexually Transmitted Infections Among Veterans

BACKGROUND

Healthcare encounters for the diagnosis and treatment of sexually transmitted infections (STIs) are common and represent an opportunity to discuss and initiate HIV pre-exposure prophylaxis (PrEP). Little is known about how frequently PrEP is discussed and initiated in association with encounters for STIs.

DESIGN

Retrospective cohort and nested case-control study, matched by STI date, in national Veterans Health Administration (VHA) facilities  from January 2013 to December 2018.

PARTICIPANTS

Veterans with a first STI diagnosis (i.e., early syphilis, gonorrhea, or chlamydia) based on ICD codes, excluding those with prior HIV diagnosis, prior PrEP use, or STI diagnosed on screening during a visit to initiate PrEP.

MAIN MEASURES

Frequency of PrEP initiation within 90 days of healthcare encounter for STIs. In the case-control study, we performed a structured chart review from the initial STI-related clinical encounter and quantified frequency of PrEP discussions among matched patients who did and did not initiate PrEP in the following 90 days.

KEY RESULTS

We identified 23,312 patients with a first STI, of whom 90 (0.4%) started PrEP within 90 days. PrEP initiation was associated with urban residence (OR = 5.0, 95% CI 1.8-13.5), White compared to Black race (OR = 1.7, 95% CI 1.0-2.7), and syphilis diagnosis (OR = 5.7, 95% CI 3.7-8.6). Chart review revealed that discussion of PrEP was rare among people with STIs who did not subsequently start PrEP (1.1%, 95% CI 0.1-4.0). PrEP initiation was associated with documentation of sexual history (80.0% of initiators vs. 51.0% of non-initiators, p < 0.01) and discussion of PrEP (52.2% vs. 1.1%, p < 0.01) during the initial STI diagnosis encounter.

CONCLUSIONS

Discussion and initiation of PrEP were rare following healthcare encounters for STIs. Interventions are needed to improve low rates of sexual history-taking and discussion of PrEP during healthcare encounters for STIs.

Graphical analysis of guideline adherence to detect systemwide anomalies in HIV diagnostic testing

Background

Analyses of electronic medical databases often compare clinical practice to guideline recommendations. These analyses have a limited ability to simultaneously evaluate many interconnected medical decisions. We aimed to overcome this limitation with an alternative method and apply it to the diagnostic workup of HIV, where misuse can contribute to HIV transmission, delay care, and incur unnecessary costs.

Methods

We used graph theory to assess patterns of HIV diagnostic testing in a national healthcare system. We modeled the HIV diagnostic testing guidelines as a directed graph. Each node in the graph represented a test, and the edges pointed from one test to the next in chronological order. We then graphed each patient’s HIV testing. This set of patient-level graphs was aggregated into a single graph. Finally, we compared the two graphs, the first representing the recommended approach to HIV diagnostic testing and the second representing the observed patterns of HIV testing, to assess for clinical practice deviations.

Results

The HIV diagnostic testing of 1.643 million patients provided 8.790 million HIV diagnostic test results for analysis. Significant deviations from recommended practice were found including the use of HIV resistance tests (n = 3,007) and HIV nucleic acid tests (n = 16,567) instead of the recommended HIV screen.

Conclusions

We developed a method that modeled a complex medical scenario as a directed graph. When applied to HIV diagnostic testing, we identified deviations in clinical practice from guideline recommendations. The model enabled the identification of intervention targets and prompted systemwide policy changes to enhance HIV detection.

Improving quality of hepatitis B care in the Veteran's Health Administration

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Robust Hepatitis A Vaccination Response Within the United States Veterans Health Administration in the Wake of State Outbreaks

We assessed hepatitis A (HepA) vaccine receipt among susceptible individuals in outbreak and matched nonoutbreak states. Difference-in-differences models and multivariable logistic regression were used to compare HepA vaccination rates in these states. In the postoutbreak year, there was a 112% increase in HepA vaccinations in outbreak states versus a 6% decrease in nonoutbreak states. Differences persisted in our multivariable model (adjusted odds ratio = 2.53; 95% confidence interval = 2.45, 2.61). HepA vaccination rates increased dramatically in outbreak states, but many individuals susceptible to hepatitis A virus remain unvaccinated. (Am J Public Health. Published online ahead of print May 26, 2022: e1-e5. https://doi.org/10.2105/AJPH.2022.306845).

Hepatitis B Virus-Related Care Quality In Patients With Hepatitis B/Hiv Coinfection Versus Hepatitis B Monoinfection: A National Cohort Study

BACKGROUND

Guideline-adherent hepatitis B virus (HBV) care is critical for patients with HBV, particularly HBV-HIV co-infected patients given increased risks of liver-related complications. However, a comprehensive assessment of HBV-related care in HBV-HIV coinfected patients is lacking.

METHODS

We retrospectively assessed adherence to HBV-related care guidelines in all patients with HBV-HIV co-infection and HBV monoinfection (HBV-M) in the national Veterans Health Administration healthcare system in 2019.

RESULTS

We identified 1,021 patients with HBV-HIV among 8,323 veterans with chronic HBV. Adherence to HBV guidelines was similar or better in HBV-HIV versus HBV-M, including HBV treatment (97% vs. 71%), biannual hepatocellular carcinoma (HCC) surveillance (55% vs. 55%) for patients with cirrhosis, HAV screening (69% vs. 56%), HCV screening (100% vs. 99%), and on-therapy ALT monitoring (95% vs. 96%).Compared to those seeing gastroenterology (GI) or infectious diseases (ID) providers, patients without specialty care were less likely to receive antiviral treatment (None:39%, GI:80%, ID:84%) or HCC surveillance (None: 16%, GI: 66%, ID:47%). These findings persisted in multivariable analysis. Compared with ID care alone, a higher proportion of HBV-HIV patients seen dually by GI and ID received HCC surveillance (GI+ID:73% vs. ID:31%) and on-therapy HBV-DNA monitoring (GI+ID: 82%, ID: 68%).

CONCLUSIONS

HBV-HIV patients received similar or higher rates of guideline-adherent HBV-related care than HBV-M patients. HBV-HIV patients under dual GI and ID care achieved higher quality care compared to ID care alone. Specialty care was independently associated with higher quality HBV care in HBV-HIV and HBV-M patients.

Differences in Syphilis Incidence Using a Laboratory Algorithm in People With and Without HIV in an 11-Year Nationwide Cohort Study

Background

To measure the incidence of syphilis diagnoses among people with HIV vs those without HIV in a national multiyear retrospective cohort.

Methods

Treponemal and nontreponemal tests, HIV status, and demographic data were identified among all individuals receiving Veterans Health Administration (VHA) care between January 1, 2009, and December 31, 2019. Syphilis testing rates and incident syphilis diagnoses as defined by a laboratory algorithm were stratified by HIV status.

Results

Syphilis was diagnosed in 1.2% (n = 2283) of 194 322 tested individuals in VHA care in 2019. Among individuals with HIV tested for syphilis, 6.1% met criteria for syphilis compared with 0.7% without HIV. Syphilis incidence in 2019 was 35/100 000, a 17% increase from 2009 (30/100 000). In 2019, syphilis incidence was 3381 per 100 000 persons among individuals with HIV and 19 per 100 000 in those without HIV.

Conclusions

Using a laboratory-based diagnostic algorithm, a 178-fold difference in syphilis incidence was observed between individuals with and without HIV in 2019. US syphilis incidence data that incorporate HIV status are needed. Interventions to monitor and prevent sexually transmitted infections should address the role of HIV status.

Testing practices and incidence of chlamydial and gonococcal infection in the Veterans Health Administration, 2009-2019

BACKGROUND

Chlamydia trachomatis and Neisseria gonorrhoeae cases reached a record high in the United States in 2018. Although active duty military servicemembers have high rates of chlamydia and gonorrhea infection, trends in chlamydia and gonorrhea in the Veterans Health Administration (VHA) system have not been previously described, including among patients with human immunodeficiency virus (HIV) and young women.

METHODS

We identified all Veterans in VHA care from 2009-2019. Tests and cases of chlamydia and gonorrhea were defined based on lab results in the electronic health record. Chlamydia and gonorrhea incidence rates were calculated each year by demographic group and HIV status.

RESULTS

In 2019, testing for chlamydia and gonorrhea occurred in 2.3% of patients, 22.6% of women ages 18-24, and 34.1% of persons with HIV. 2019 incidence of chlamydia and gonorrhea was 100.8 and 56.3 cases per 100,000 VHA users, an increase of 267% and 294%, respectively, since 2009. Veterans aged <34 years accounted for 9.5% of the VHA population but 66.9% of chlamydia and 42.9% of gonorrhea cases. Chlamydia and gonorrhea incidence rates in persons with HIV were 1,432 and 1,687 per 100,000, respectively.

CONCLUSIONS

The incidence of chlamydia and gonorrhea rose dramatically from 2009-2019. Among tested persons, those with HIV had a 15.2-fold higher unadjusted incidence of chlamydia and 34.9-fold higher unadjusted incidence of gonorrhea compared to those without HIV. VHA-wide adherence to chlamydia and gonorrhea testing in high-risk groups merits improvement.

Access to Comprehensive Services for Advanced Liver Disease in the Veterans Health Administration

BACKGROUND

The Veterans Health Administration (VHA) provides care to the one of the largest cohorts of patients with advanced liver disease (ALD) in the USA.

AIMS

We performed a national survey to assess system-wide strengths and barriers to care for Veterans with ALD in this national integrated healthcare setting.

METHODS

A 52-item survey was developed to assess access and barriers to care in Veterans with ALD. The survey was distributed to all VHA medical centers in 2015. Results were analyzed using descriptive statistics.

RESULTS

One hundred and fifty-three sites responded to this survey. Multidisciplinary services were available on-site at > 80% of sites. Ninety-five percent of sites had mental health and addictions treatment available, with 14% co-locating these services within the liver clinic. Few sites (< 25%) provided pharmacologic treatment for alcohol use disorder in primary care or hepatology settings. Seventy-two percent of sites reported at least one barrier to liver-related care. Of the sites reporting at least one barrier, 53% reported barriers to liver transplant referral, citing complex processes and lack of staff/resources to coordinate referrals. Palliative care was widely available, but 61% of sites reported referring < 25% of their patients with ALD for palliative services.

CONCLUSION

Multidisciplinary services for Veterans with ALD are widely available at VHA sites, though barriers to optimal care remain. Opportunities for improvement include the expansion of providers with hepatology expertise, integrating pharmacotherapy for alcohol use disorder into hepatology and primary care, streamlining the transplant referral process, and expanding palliative care referrals for patients with ALD.

Alanine Aminotransferase Results Differ by Analyzer Manufacturer in a National Integrated Health Setting, 2012-2017

CONTEXT.—

Disease guidelines specify universal alanine aminotransferase (ALT) thresholds for clinical decision-making, yet the effect of variability among ALT analyzers remains unclear.

OBJECTIVE.—

To compare ALT results from different analyzers from 2012-2017.

DESIGN.—

Veterans Health Administration (VHA) laboratories perform external ALT proficiency testing using standardized College of American Pathologists (CAP) samples in analyzers by 5 manufacturers. In this operational analysis, we evaluated 22 950 ALT values from 80 independent CAP samples tested at 223 laboratories. Using mixed effects modeling, we estimated the association between analyzer manufacturer and CAP outcome, adjusting for manufacturer, facility, and calendar year. We performed subgroup analyses on CAP samples with overall means near clinical guideline-specified thresholds, including less than 50 U/L (n = 10) and less than 35 U/L (n = 5).

RESULTS.—

The VHA used Abbott Laboratories (n = 3175; 14%), Beckman Coulter Diagnostics (n = 8723; 38%), Roche Diagnostics (n = 2595; 11%), Siemens Healthineers USA (n = 5713; 25%), and Vitros/Ortho Clinical Diagnostics (n = 2744; 12%) analyzers. The CAP samples (n = 80 samples, n = 22 950 tests) covered a wide range of mean ALT values (21-268 U/L). The average difference in mean ALT value per sample between the highest-reading and lowest-reading manufacturers was 15.4 U/L (SD = 1.8) for the 10 samples with mean ALT less than 50 U/L, and it was 10.4 U/L (SD = 3.6) overall (n = 80). In linear mixed effects modeling, we found statistically significant differences in ALT values between the different manufacturers in each year.

CONCLUSIONS.—

We found statistically and clinically meaningful differences between analyzers across the ALT spectrum in each year, including at ALT levels lower than 50 U/L and lower than 35 U/L. Universal ALT thresholds should be avoided as a trigger for clinical action until differences between analyzers can be resolved.

Health Care Facility Characteristics are Associated with Variation in Human Immunodeficiency Virus Pre-exposure Prophylaxis Initiation in Veteran's Health Administration

To quantify health care facility-level variation in pre-exposure prophylaxis (PrEP) use in the Veteran's Health Administration (VHA); to identify facility characteristics associated with PrEP use. Retrospective analysis of the health care facility-level rate of PrEP initiation in VHA through June 30, 2017. Standardized PrEP initiation rates were used to rank facilities. Characteristics of facilities, prescribers, and PrEP recipients were examined within quartiles. Multiple linear regression was used to identify associations between facility characteristics and PrEP use. We identified 1600 PrEP recipients. Mean PrEP initiation rate was 20.0/100,000 (SD 22.8), ranging from 3.0/100,000 (SD 2.0) in the lowest quartile to 48.1/100,000 (SD 29.1) in the highest. PrEP prescribing was positively associated with proportions of urban dwellers and individuals < 45, tertiary care status, and location. Variability in PrEP uptake across a national health care system highlights opportunities to expand access in non-tertiary care facilities and underserved areas.

Hepatitis C Cure Is Associated with Decreased Healthcare Costs in Cirrhotics in Retrospective Veterans Affairs Cohort

BACKGROUND

Approximately 233,898 individuals in the Veterans Affairs healthcare network are hepatitis C virus (HCV)-infected, making the Veterans Affairs the single largest provider of HCV care in the USA. Direct-acting antiviral treatment regimens for HCV offer high cure rates. However, these medications pose an enormous financial burden, and whether HCV cure is associated with decreased healthcare costs is poorly defined.

AIMS

To measure downstream healthcare costs in a national population of HCV-infected patients up to 9 years post-HCV antiviral treatment, to compare downstream healthcare costs between cured and uncured patients, and to assess impact of cirrhosis status on cost differences.

METHODS

This is a retrospective cohort study (2004-2014) of hepatitis C-infected patients who initiated antiviral treatment within the United States Veterans Affairs healthcare system October 2004-September 2013. We measured inpatient, outpatient, and pharmacy costs after HCV treatment.

RESULTS

For the entire cohort, cure was associated with mean cumulative cost savings in post-treatment years three-six, but no cost savings by post-treatment year nine. By post-treatment year nine, cure in cirrhosis patients was associated with a mean cumulative cost savings of $9474 (- 32,666 to 51,614) per patient, while cure in non-cirrhotic patients was associated with a mean cumulative cost excess of $2526 (- 12,211 to 7159) per patient.

CONCLUSIONS

Among patients with cirrhosis at baseline, cure is associated with absolute cost savings up to 9 years post-treatment compared to those without cure. Among patients without cirrhosis, early post-treatment cost savings are counterbalanced by higher costs in later years.

Achieving Excellence in Hepatitis B Virus Care for Veterans in the Veterans Health Administration

Enhancing care of veterans infected with hepatitis B virus who are in VHA care includes providing clinical guidance, informatics tools, patient monitoring, and continuous evaluation of care.

Hepatitis A Virus Prevention and Vaccination Within and Outside the Veterans Health Administration in Light of Recent Outbreaks

Although widespread hepatitis A vaccination has dramatically decreased infection rates, a large proportion of VA patients in traditionally high-risk groups remains susceptible to infection.

Accessibility and Uptake of Pre-Exposure Prophylaxis for HIV Prevention in the Veterans Health Administration

To increase access, the National PrEP Working Group is expanding outreach outside of primary care and among nonspecialists, ensuring uniformly high-quality care and targeting high-risk populations.

[Functional and Morphological Microstructural Changes in SD-OCT in Long-Term Treatment for Neovascular AMD with Ranibizumab - Monotherapy Versus Combination Therapy with PDT]

Background: Intravitreal anti-VEGF therapy is the gold standard in the treatment of neovascular age-related macular degeneration (nAMD). In recent literature, the benefit of additional photodynamic therapy (PDT) has been debated. The aim of our study was to compare the functional and structural effects of long-term combination therapy with PDT plus ranibizumab with monotherapy with ranibizumab. Material and Methods: In a retrospective study, patients suffering from nAMD were followed up for at least 42 months. Patients were assigned to group A (monotherapy with ranibizumab according to pro re nata [PRN]) or group B (combination therapy with one-time PDT plus ranibizumab according to PRN). The best-corrected visual acuity (BVCA) was evaluated at the starting and end points, together with central retinal thickness (CRT), maximal retinal thickness (MRT) and the maximal diameter of the base of the subretinal plaque in spectral-domain optical coherence tomography (SD-OCT), at the first measurement and at the end point. Results: Group A consisted of 21 eyes (17 patients) and group B consisted of 12 eyes (11 patients). The average follow-up from starting to end point was 64 months and 47 months, from the first measurement of SD-OCT to the end point. Within this period, patients in group A received 19 ± 14 intravitreal injections, and patients in group B received 22 ± 10 intravitreal injections. BCVA at the starting point was 0.31 ± 0.26 in group A and 0.31 ± 0.17 in group B. At the end point, BCVA in group A was 0.29 ± 0.25 (p = 0.405), and in group B 0.25 ± 0.20 (p = 0.142). CRT decreased in group A by 72 ± 178 µm (p = 0.024) and group B by 28 ± 98 (p = 0.1335). MRT decreased in group A by 25 ± 135 µm (p = 0.166) and in group B by 2 ± 118 µm (p = 0.421). The base of the subretinal plaque increased in group A by 32 ± 1468 µm (p = 0.242) and in group B by 748 ± 1024 (p = 0.025). Conclusion: In a long-term follow-up of 5.3 years, patients with nAMD in both groups exhibited good stabilisation of visual acuity. In both groups, retinal thickness decreased and the base of the subretinal plaque increased. With respect to SD-OCT morphological criteria, patients in group A (monotherapy) responded slightly better to therapy than patients in group B (combination group).

Double robust estimator of average causal treatment effect for censored medical cost data

In observational studies, estimation of average causal treatment effect on a patient's response should adjust for confounders that are associated with both treatment exposure and response. In addition, the response, such as medical cost, may have incomplete follow-up. In this article, a double robust estimator is proposed for average causal treatment effect for right censored medical cost data. The estimator is double robust in the sense that it remains consistent when either the model for the treatment assignment or the regression model for the response is correctly specified. Double robust estimators increase the likelihood the results will represent a valid inference. Asymptotic normality is obtained for the proposed estimator, and an estimator for the asymptotic variance is also derived. Simulation studies show good finite sample performance of the proposed estimator and a real data analysis using the proposed method is provided as illustration. Copyright © 2016 John Wiley & Sons, Ltd.

Cascade of Care for Hepatitis C Virus Infection Within the US Veterans Health Administration

OBJECTIVES

We measured the quality of HCV care using a cascade of HCV care model.

METHODS

We estimated the number of patients diagnosed with chronic HCV, linked to HCV care, treated with HCV antivirals, and having achieved a sustained virologic response (SVR) in the electronic medical record data from the Veterans Health Administration's Corporate Data Warehouse and the HCV Clinical Case Registry in 2013.

RESULTS

Of the estimated 233,898 patients with chronic HCV, 77% (181,168) were diagnosed, 69% (160,794) were linked to HCV care, 17% (39,388) were treated with HCV antivirals, and 7% (15,983) had achieved SVR.

CONCLUSIONS

This Cascade of HCV Care provides a clinically relevant model to measure the quality of HCV care within a health care system and to compare HCV care across health systems.

[Morphological Characteristics in SD-OCT and Fundus Autofluorescence in Different Ischaemic Retinopathies - Characterisation of a New, Temporary Hyperreflective Band]

BACKGROUND

The aim of this study was to investigate alterations in the neurosensory retinal morphology secondary to acute retinal ischaemic conditions. The observations were documented by spectral domain optical coherence tomography (SD-OCT, Heidelberg Engineering) and fundus autofluorescence (FAF) imaging. In addition, the occurrence of an additional hyperrefelctive band in the outer corneal layers is described. This observation was made during the evaluation of OCT images of patients with an acute loss of vision due to retinal ischaemia.

PATIENTS/METHOD

SD-OCT images and FAF were used to observe the retinal structure of 26 subjects (36 to 96 years) with acute monocular visual impairment due to central retinal artery occlusion (CRAO), branch retinal artery occlusion (BRAO), anterior ischaemic optic neuropathy (AION) or impending central retinal vein occlusion were included. The main focus of attention was set on the transition of the outer nuclear layer (ONL) to outer plexiform layer (OPL). Furthermore measurements of the retinal thickness at the fovea, parafoveal and within the retinal layers were acquired and compared to corresponding points of the non-affected eyes. SD-OCT images were acquired with a combined SD-OCT and scanning laser ophthalmoscope (cSLO) imaging system using a linear cross hair scan and a 6 line radial scan of 6 mm length (ART mode on; average of 20 frames).

RESULTS

SD-OCT revealed an additional highly reflective band located within the OPL. Morphological characteristics of this hyperdense band were a decreasing intensity with distance from the fovea, partially segmental occurrence and manifestation limited in time. FAF showed areas of increased and decreased signal intensity within the vessel arcade at the posterior pole. The regions of decreased FAF corresponded to perivenous regions and resemble the "frosted branches" sign seen in fluorescein angiography in patients with ocular ischaemia.

CONCLUSIONS

The additional hyperreflective band observed in SD-OCT could represent a marker for retinal ischaemia in subjects without the presence of a complete vascular occlusion. The mid retinal localisation of the band within the OPL is situated at the locus of transition from retinal to choroidal oxygen supply where oxygen diffusion is weakest. Histopathologically the observed structure could represent activated microglial tissue induced by the hypoxia driven upregulation of inflammatory molecules aimed at ischaemia repair.

Hepatitis C treatment eligibility among HIV-hepatitis C virus coinfected patients in Oregon: a population-based sample

Approximately 287,000 individuals in the USA are coinfected with HIV and hepatitis C. Recently, new hepatitis C regimens have become available, increasing rates of sustained virologic response in the monoinfected, with studies evaluating their success in the coinfected under way. Previous investigators estimated eligibility for hepatitis C therapy among the coinfected patients, but all had significant methodological limitations. Our study is the first to use a multi-year, statewide, population-based sample to estimate treatment eligibility, and the first to estimate eligibility in the setting of an interferon-free regimen. In a population-based sample of 161 patients infected with HIV and hepatitis C living in Oregon during 2007-2010, 21% were eligible for hepatitis C therapy. Despite the anticipation surrounding an interferon-sparing regimen, eligibility assuming an interferon-free regimen increased only to 26%, largely due to multiple simultaneous contraindications. Obesity was described for the first time as being associated with decreased eligibility (OR: 0.11). Active alcohol abuse was the most common contraindication (24%); uncontrolled mental health (22%), recent injection drug use (21%), poor antiretroviral adherence (22%), and infection (21%) were also common excluding conditions. When active drug or alcohol abuse was excluded as contraindications to therapy, the eligibility rate was 34%, a 62% increase. Assuming an interferon-free regimen and the exclusion of active drug or alcohol abuse as contraindications to therapy, the eligibility rate increased to 42%. Despite the availability of direct-acting anti-viral regimens, eligibility rates in HIV-hepatitis C virus (HCV) coinfection are modest. Many factors precluding hepatitis C therapy are reversible, and targeted interventions could result in increased eligibility.

[Vitreomacular Traction Syndrome (VMTS)]

In vitreomacular traction syndrome (VMTS) an anomalous posterior vitreous detachment (APVD) with persistant symptomatic vitreoretinal adhesion is seen. The adhesion leads to a thickened macula, to macular oedema and a reduction of BCVA. Modern imaging techniques like spectral domain OCT (SD-OCT) allow a detailed imaging of the retinal microstructure and the vitreoretinal interface. Vitreomacular adhesions and their effect on the retina can be visualised. Until now, the treatment option for VMTS was and is vitreoretinal surgery. In studies pharmacological vitreolysis has shown a therapeutic effect in patients with symptomatic adhesion and traction. The results of these studies represent an important step towards a pharmacological treatment of VMTS.

[Transconjunctival sutureless pars plana vitrectomy and Brilliant Peel (BP)-assisted ILM peeling in patients with macular holes]

PURPOSE

The aim of this study was to evaluate the visual and anatomic outcome after 23-gauge transconjunctival sutureless pars plana vitrectomy and Brilliant Peel (BP)-assisted ILM peeling in patients with macular holes.

METHODS

In a consecutive retrospective study in 41 eyes of 41 patients with macular holes a standardised 23-G transconjunctival sutureless pars plana vitrectomy with ILM-peeling and gas tamponade was performed. All patients underwent preoperative measurements of visual acuity (VA), the maximum hole diameter, basis, height, and intraretinal changes using high resolution optical coherence tomography (SD-OCT; Spectralis; Heidelberg Engineering). Main outcome measures included visual acuity 1, 3, and 6 months after surgery and the closure rate. We also evaluated photoreceptor inner/outer segment (IS/OS) integrity as seen in SD-OCT for correlation with visual outcomes after macular hole surgery.

RESULTS

At baseline the mean best corrected visual acuity (BCVA) was 0.2 (0.77 logMAR). BCVA improved significantly to 0.4 (0.46 logMAR) after 1 month, to 0.44 (0.41 logMAR) after 3 months and to 0.58 (0.28 logMAR) after 6 months, respectively. A closure rate of 95.1 % was achieved. The morphological parameter photoreceptor IS/OS integrity was measured semiquantitatively and showed a positive correlation to BCVA.

CONCLUSION

Transconjunctival sutureless pars plana vitrectomy and Brilliant Peel (BP)-assisted ILM peeling in patients with macular holes is a very safe procedure and leads to good functional and anatomic results. The integrity of the IS/OS segment is a good predictive parameter for BCVA improvement after macular hole surgery.

[Choroidal neovascularisation in pathological myopia: epidemiological data from a health services research study conducted in Germany]

BACKGROUND

Pathological myopia (PM) or high myopia is defined as excessive short-sightedness (more than -6 dioptres) caused by a strong dilation of the bulbus oculi, that can induce the development of new and unstable vessel structures [choroidal neovascularisation (CNV)]. Since there are only limited epidemiological data available on PM, this health services research study was conducted.

PATIENTS AND METHODS

A health services survey with ophthalmologists throughout Germany was undertaken. Physicians were asked to complete a 51-item questionnaire on CNV in PM as well as on its early stages in their daily practice, diagnosis, control and treatment, patient numbers and evaluation of health care situation. Statistical analyses were entirely descriptive.

RESULTS

Of 7,500 ophthalmologists, a representative sample of 800 was randomly selected; 340 physicians took part. The mean prevalence rates/year/practice were 1,765.5 ± 1,218.1 with myopia, 230.7 ± 278.6 patients with high myopia, subdivided into 129.3 ± 242.8 patients with PM without macular degeneration (MD), 39.6 ± 64.8 patients with PM and MD, and 13.3 ± 30.3 patients with PM and CNV. Data on diagnosis and control show a lack of clearly defined standardisation. With regard to treatment of CNV in PM the data show the current discrepancy of guideline recommendations and approved treatment options.

CONCLUSION

The prevalence and incidence data collected in this study vary considerably between physicians. This may be explained by the various grades of specialisation as well as to possibly existing uncertainties regarding the definition and nomenclature of PM/high myopia and their different stages of the disease that should be harmonised. A generally accepted definition of severity grades, recommendations on diagnosis as well as detailed information and continuous training programmes on this disease is necessary.

[Acute loss of vision during therapy of chronic hepatitis C]

A patient undergoing combined therapy of chronic hepatitis C with pegylated interferon-α-2a (PEG-IFN-α-2a) and ribavirin suddenly developed severe loss of visual acuity. A central vein occlusion with macular edema was found and intravitreal injections of bevacizumab were initiated. Retinal occlusion is a known complication of therapy with pegylated interferon-α-2a and ribavirin. An interdisciplinary assessment of patients treated for a chronic hepatitis C as well as an early anti-VEGF administration can be helpful in the therapy of this complication of chronic hepatitis C.

[Epi-LASIK with a 1000 hertz excimer laser]

PURPOSE

The aim of this study was to evaluate the safety, stability and efficacy of Epi-LASIK with a 1000 hertz excimer laser system.

METHODS

40 eyes of 23 patients underwent an Epi-LASIK procedure using the Gebauer EpiLift and the WaveLight Concept System 1000. Preoperatively as well as 1 month, and 3 months postoperatively, a complete ophthalmic examination, including objective and subjective refraction (UCVA, BCVA) and topography, was performed.

RESULTS

The mean preoperative spherical equivalent (SE) was -4.07 D (SD ± 1.89 D). 1 month after surgery, the spherical equivalent was + 0.01 D (SD ± 0.33 D), and 3 months after surgery -0.06 D (SD ± 0.28 D). 3 months after the Epi-LASIK procedure, 90 % of the patients were within ± 0.5 D of the intended correction, and 97.5 % were within ± 1.0 D of the intended correction. The astigmatism was reduced from -0.77 D (SD ± 0.68 D) to -0.24 D (SD ± 0.29 D) 3 months after surgery. 34 of the 40 eyes had a clear cornea 3 months after surgery, and 6 of the 40 eyes presented with haze grade 0.5.

CONCLUSIONS

In our pilot series of 40 eyes, the use of the 1000 hertz excimer laser did not reveal any specific clinical side effects potentially associated with the use of a high repetition rate. These first results with Epi-LASIK and the WaveLight Concept System 1000 are very promising.

[Sutureless encircling band - clinical experience]

PURPOSE

In cases with multiple retinal breaks and in combination with vitrectomy in eyes with proliferative vitreoretinopathy (PVR) often an encircling band is used for retinal detachment surgery. Usually the encircling band is fixed with non-resorbable sutures.

METHODS

A fixation method for an encircling band in retinal detachment surgery with one scleral tunnel in each of the 4 quadrants is reported. After 50 consecutive operations on 50 patients, we describe our experience and biomechanical calculations of this fixation technique.

RESULTS

In comparison to conventional fixation technique we found the following advantages. No suture is necessary, this means that no additional foreign body can produce irritations. The scleral tunnel is safe and the preparation under the microscope can be performed rapidly and under good control. According to our biomechanical calculations, the same tension of the encircling band produces less myopic shift with this technique. Scleral tunnel fixation is very comfortable in combination with a vitrectomy.

CONCLUSIONS

After a short learning curve, the operating time is as short as with conventional suture fixation of the encircling band. There is less perforating risk, less irritation and less patient discomfort postoperatively. A sutureless encircling band with scleral tunnel fixation is a very useful operative technique in clinical routine.

[Intravitreal Ranibizumab Injection for the Treatment of Occult and Classic CNV in Exsudative AMD]

BACKGROUND

Double-blind, randomised, placebo-controlled and multicentre studies have proven an increase in visual acuity in one-third of the patients receiving Ranibizumab (0.5 mg) injections, who suffer from exsudative AMD. The purpose of this study was to evaluate the early effects of intravitreal Ranibizumab therapy in patients with mainly occult neovascular AMD in clinical applications.

PATIENTS AND METHODS

In a retrospective cohort study, 91 eyes with occult and classic neovascular AMD were treated with intravitreal injections of Ranibizumab (0.5 mg) at 30-day intervals. The treatment effects were evaluated according to best corrected visual acuity, optical coherence tomography (OCT) and intraocular pressure at baseline as well as 1, 3 and 6 months after the beginning of therapy. Furthermore, fluorescein angiography (FLA) was performed at baseline as well as 3 and 6 months after therapy.

RESULTS

74 % of the patients lost fewer than 15 letters on the EDTRS-scale 6 months after the beginning of therapy. Visual acuity improved by more than 15 letters in 11 % of the patients. Central retinal thickness, measured by OCT, decreased statistically significantly in each control compared to baseline (1 month: p = 0.045; 3 months: p = 0.001; 6 months: p = 0.006). Leakage and membranes, evaluated in FA, worsened in 31 % of the patients; in 67 % the findings were stable. No increase in intraocular pressure was detected.

CONCLUSIONS

Intravitreal application of Ranibizumab was safe and well tolerated. In the clinical situation, visual acuity was stabilised in the short term. As opposed to phase-III studies, no improvement in visual acuity could be accomplished. Cental retinal thickness decreased and findings in fluorescein angiography were stable within a 6-month follow-up period. It is necessary to perform monthly controls and proceed with VA- and OCT-based injections in order to maintain the therapeutic effect. Futher clinical evaluations of Ranibizumab will be necessary to evaluate its long-term treatment effects.

[Wavefront-guided and wavefront-optimised LASEK--comparison of clinical results]

PURPOSE

The aim of this study was to compare refractive outcomes and wavefront results in eyes undergoing wavefront-optimised and wavefront-guided LASEK.

METHODS

In this contralateral eye study wavefront-guided LASEK and wavefront-optimised LASEK have been carried out on 30 eyes each. Preoperatively, 1 month, 3 months and 6 months after surgery a full ophthalmological examination was carried out. Preoperatively and 6 months postoperatively additional wavefront measurement have been carried out on all patients.

RESULTS

The mean preoperative refraction in the wavefront-guided group was -4.41 D (SD 1.38 D) and in the wavefront-optimised group -4.62 D (SD 1.86 D). The postoperative refraction was very good in both groups (wavefront-guided -0.06 D, SD 0.18 D; wavefront-optimised -0.03 D, SD 0.21 D). In both groups RMS of higher orders were increased slightly (wavefront-guided from 0.26 to 0.31 microm, wavefront-optimised from 0.27 to 0.32 microm) and also spherical aberrations increased slightly (wavefront-guided from 0.18 to 0.23 microm, wavefront-optimised from 0.16 to 0.21 microm).

CONCLUSIONS

The refractive results with the Concept System 500 in patients with preoperatively low amounts of higher order aberrations after wavefront-guided and wavefront-optimised LASEK are comparable. As good wavefront measurements need a lot of experience and take a lot of time, there is no advantage of wavefront-guided ablation in patients with low preoperative aberrations.

[Cut quality of a new femtosecond laser system]

OBJECTIVE

The aim of this study was to evaluate the cut quality and the cellular damage when using a new 200 kHz femtosecond laser.

METHODS

20 porcine eyes and 3 human eyes, not suitable for transplantation, were used for this study. The WaveLight UltraFlap femtosecond laser was used for flap creation. The surface of the cornea, the structure and ultrastructure of the corneal cells and stroma were evaluated thoroughly using light microscopy (HE-, PAS- and Picrosirius red staining), transmission electron microscopy (TEM), and scanning electron microscopy (SEM).

RESULTS

In all eyes, the flap could be lifted very easily and the flap appeared very smooth. Structural and ultrastructural evaluation with light and transmission electron microscopy on epithelium and endothelium showed no side effects of the laser application. The area around the flap cut was minimally affected and the keratocytes and collagen fibres showed minimal alteration due to laser treatment. Scanning electron microscopy revealed in all cases smooth surfaces and precise sidecuts.

CONCLUSIONS

Precise corneal flaps can easily be created with this new femtosecond laser. At the same time, no structural and thermal side effects on corneal epithelium, stroma and endothelium appeared. Hence with this new femtosecond laser corneal flaps could be created easily without noteworthy side effects.

On and Off magnetic auditory evoked responses in early infancy: a possible marker of brain immaturity

OBJECTIVE

To follow the development of the auditory evoked on- and off-responses in early infancy.

METHODS

The subjects were healthy infants, studied at conceptional age (CA) 39-66 weeks. Serial auditory evoked responses (AERs) were recorded in 17 subjects in response to tones of frequency 1.5 kHz and duration 1.0 s in order to follow the development of the AERs. Two small substudies were performed to examine off-responses evoked by tones of varying duration. The first used 0.2, 0.3, 0.4, and 0.5s tones; the second used 0.5, 1.0, and 2.0 s tones.

RESULTS

For the 1.0 s tones, the on- and off-responses consisted of three components: P250, P400, and N750 m. The on- and off-responses had similar amplitude, in contrast to adult AERs in which the on-responses are typically much larger. Prior to about CA 47 weeks, the on-responses were actually smaller on average than the off-responses, and in infants born prior to CA 38 weeks the AERs were dominated by the off-response. Off-responses were seen for tones as brief as 0.2 s; however, the P400m component was often absent in the off-responses for tone durations < or = 0.5 s. An interaction was observed in which the N750 m-On component was strongly suppressed when it overlapped the P250 m-Off.

CONCLUSIONS

Off-responses are much more prominent in infant than in adult AERs, especially in pre-term infants and at early CAs. On- and off-responses also exhibit more complex behavior in infants than in adult; the individual components can interact and behave independently.

SIGNIFICANCE

Measurement of auditory off-responses can improve the assessment of infant neurodevelopment, potentially providing a marker of brain immaturity.

MEG sleep pattern dependence of auditory evoked fields in young infants

We recorded magnetic auditory evoked responses (AERs) to brief 1 kHz tones in infants ranging in age from 1.5-8.5 weeks. Long continuous MEG recordings were collected with a 37-channel sensor and were classified into one of four patterns: low-amplitude irregular, high-amplitude slow, mixed, and REM-like sleep. The AERs were characterized by a monophasic deflection with nominal latency 250 msec, followed by a broader peak with opposite polarity and approximate latency 600 msec. No strong dependences on MEG sleep pattern were observed. The latency of the 250 msec component decreased with age, but the 600 msec component showed variable latency. The signal topography of both components was compatible with a source in the auditory cortex. We conclude that sleep state does not appreciably confound recording of the AER in young infants.

Comparative analysis of the human and mouse Hey1 promoter: Hey genes are new Notch target genes

Hey genes (Hey1, Hey2 and HeyL) encode a new group of basic helix-loop-helix transcription factors that are related to the hairy/Enhancer of split genes. In the present study, we cloned and characterized the promoter region of the human and mouse Hey1 gene. The transcription initiation site was located 138 nucleotides upstream of the start codon. There is a minimal sequence element (nt -30 to -247) that is essential and important for basal transcription in three different cell types. Further upstream, a highly conserved sequence block (nt -324 to -646; approximately 90% human/mouse similarity) could be identified that contains several putative binding sites for transcription factors and likely represents an important regulatory region for this gene. Cotransfection experiments demonstrated that the mHey1 promoter activity is up-regulated by the activated form of all four mammalian Notch receptors via two functional RBP-Jkappa binding sites. The other members of the Hey gene family, Hey2 and HeyL, also possess RBP-Jkappa binding sites and they are similarly responsive to Notch signaling. Thus, our data clearly demonstrate that Hey genes form a new class of Notch signal transducers that should prove to be relevant in various developmental processes.

Nonlinear functional modeling of scalp recorded auditory evoked responses to maximum length sequences

The purpose of this study was to model the adult human's scalp recorded evoked response to auditory pulses separated by varying inter pulse intervals (IPIs). The responses modeled probably reflect auditory nerve and brainstem generators. The subjects were 10 young adult humans with normal hearing. They were presented pseudo random sequences of pulses (maximum length sequences, MLSs) in order to characterize their system response. For the stimuli and the responses modeled accounting for temporal nonlinearities (interactions among the pulses) improved model performance only marginally. Nonlinear contributions to the models decreased with increasing interval between the input pulses. Increasing the memory of the model beyond 20 ms did not increase modeled performance dramatically. Model performance varied as a function of minimum IPI (MIPI) of the MLSs. At the shortest MIPI overall model performance deteriorated (due, in part, to a decrease in SNR), but nonlinear effects became relatively more important. At the longest MIPI performance also deteriorated, possibly due to the increasing influence of longer latency, more variable evoked potential components. Modeled performance generalized to responses recorded in the same recording session to the same and different MLSs. This study confirms the similarity between MLS linear kernels and conventionally averaged evoked responses--both are adapted responses reflecting the IPIs of the evoking stimuli.

Auditory evoked brain stem responses to trains of stimuli in human adults

OBJECTIVE

This study describes the effect of train length, interstimulus interval, intertrain interval (ITI), and stimulus duration on the transition from the unadapted to the adapted wave V auditory evoked brain stem response (ABR).

DESIGN

ABRs were recorded to stimuli presented at two different rates: a slow rate characterizing the unadapted response and a fast rate characterizing the adapted response. Trains of stimuli (a sequence of stimuli separated by intervals of silence) also were presented. Different stimulus parameters defining the trains were varied.

RESULTS

Given a sufficiently long ITI, the latency prolongation to the first three or four stimuli in a train was rapid. It was similar for trains differing in number of stimuli. After the first three or four stimuli, there was a more gradual latency prolongation as a function of stimulus number. Shorter ITIs had the effect of prolonging the latencies to all the stimuli in the trains, reducing the rate of latency prolongation over the first few stimuli, and causing responses to trains of different length to differ (e.g., two click train responses were shorter latency than four click train responses). An unexpected result was the latency prolongation of wave Vs after the presentation of the stimulus trains.

CONCLUSIONS

In response to a train of clicks, there seems to be a rapid increase in wave V latency to the first few clicks in the train followed by a more gradual latency prolongation to subsequent clicks in the train.

The effects of lead on otoacoustic emissions and auditory evoked potentials in monkeys

Auditory functioning was assessed in two groups of adult rhesus monkeys (11 years of age). One (n = 11) received modest exposure to lead early in life and the other (n = 8) served as controls and did not receive any lead supplementation. Two lead-exposed monkeys had abnormal distortion product otoacoustic emissions (DPEs) and smaller amplitude or absent evoked potentials. These monkeys had abnormal distortion product otoacoustic emission (DPEs) and smaller amplitude or absent evoked potentials. These monkeys had the highest blood levels recorded in their respective groups. For the remaining lead-exposed monkeys there was little difference between their DPEs and the DPEs of the control monkeys with one exception. DPE amplitudes of the control monkeys increased more rapidly as a function of stimulus level than those of the lead-exposed monkeys at most frequencies. There was also a significant but modest effect of lead exposure on the auditory brain stem evoked responses (ABRs) of these lead-exposed monkeys. There was no apparent effect on the middle latency evoked responses (MLRs), although that result could be due to the relatively greater variability of the MLR.

Auditory evoked brainstem and middle latency responses in Macaca mulatta and humans

Early (ABRs) and middle (MLRs) surface-recorded auditory evoked potentials were compared in eight adult monkeys (Macaca mulatta) and eight adult humans. Responses whose probable generators were the cochlear nucleus and lateral lemniscus were of shorter latency and larger amplitude in monkeys. Relative to humans, ABR response latencies in monkeys were less affected by stimulus intensity, stimulus rate, and masker level. In contrast, monkey amplitudes were relatively more affected by those same stimulus parameters. The most prominent MLR wave was longer in latency and greater in amplitude in humans than the homologous wave in monkeys. The reduction in amplitude of that wave with increasing rate was greater for humans than monkeys. Temporal interactions (the effect of prior stimuli on the response to current stimulation) were investigated from a non-linear systems identification framework using maximum length sequences (MLSs). Both monkey and human auditory systems were second and probably third-order systems at the levels assessed. As the separations between the stimulus pulses decreased, evidence for temporal interactions became more prominent, reached a maximum, and then decreased with further decreases in stimulus pulse separation. At the highest stimulus rates presented, variations in temporal spacing among stimuli had less of an effect on monkey than human evoked responses.

A comparison of binaural interactions using traditional and maximum length sequence evoked response paradigms

OBJECTIVE

Two paradigms, the traditional binaural interaction (BI) paradigm and a maximum length sequence (MLS) BI paradigm were evaluated to investigate BI effects.

DESIGN

Evoked response BI effects were assessed at different levels of the auditory pathway in two experiments. Each experiment consisted of three conditions: a traditional BI paradigm using conventional stimuli, a traditional BI paradigm using MLS stimuli, and a MLS BI paradigm using MLS techniques to recover kernels reflecting BIs. Eleven normal-hearing young adults served as subjects.

RESULTS

There was evidence for BI effects on the auditory evoked brain stem response (ABR) and the middle latency response (MLR) using the traditional BI paradigm and conventional stimuli. With the same paradigm and MLS stimuli there was evidence for BI effects on the MLR but not the ABR. The more robust conventional effects may be explained by the larger amplitude evoked responses recorded conventionally due to the slower stimulation rates and more efficient signal to noise enhancement. BI effects were observed for both the ABR and MLR by recording BI kernels in the MLS BI paradigm.

CONCLUSIONS

MLS BI kernels can be recorded in normal hearing adults. The MLS BI paradigm offers three potential advantages in recording binaural effects; avoidance of some of the methodological problems associated with traditional BI paradigms, faster stimulus rates permitting a more complete characterization of binaural rate effects, and more rapid data collection.