Pressure Injury Development in Patients Treated by Critical Care Air Transport Teams: A Case-Control Study.

BACKGROUND: The US Air Force transports critically ill patients from all over the world, with transport times commonly ranging from 6 to 11 hours. Few outcome measures have been tracked for these patients. Traditional methods to prevent pressure injuries in civilian hospitals are often not feasible in the military transport environment. OBJECTIVES: The incidence rate and risk factors are described of en route-related pressure injuries for patients overseen by the Critical Care Air Transport Team. METHODS: This retrospective, case-control, medical records review investigated risk factors for pressure injury in patients who developed a pressure injury after their transport flight compared with those with no documented pressure injuries. RESULTS: The pressure injury rate was 4.9%. Between 2008 and 2012, 141 patients in whom pressure injuries developed and who had received care by the team were matched with 141 patients cared for by the team but did not have pressure injury. According to regression analysis, body mass index and 2 or more Critical Care Air Transport Team transports per patient were associated with pressure injury development. CONCLUSION: Although the pressure injury rate of 4.9% in this cohort of patients is consistent with that reported by civilian critical care units, the rate must be interpreted with caution, because civilian study data frequently represent the entire intensive care unit length of stay. Targeted interventions for patients with increased body mass index and 2 or more critical care air transports per patient may help decrease the development of pressure injury in these patients.

Statins and Musculoskeletal Conditions in U.S. Air Force Active Duty Aviators.

BACKGROUND: The purpose of this study was to examine the association of statin use and musculoskeletal conditions within the population of U.S. Air Force active duty aviators. METHODS: The study was a retrospective cohort analysis of aviators between 2004-2014 as identified from personnel data. Based on pharmacy data, participants were divided into two groups: statin users (received a statin for at least 90 d) and nonusers (never received a statin throughout the study period). Using participants' baseline characteristics, a propensity score was generated and used to match statin users to nonusers in a 1:6 ratio. Conditional logistic regression was used to determine the odds ratio for a musculoskeletal condition. RESULTS: A total of 19,330 participants met study criteria (131 statin users and 19,199 nonusers). Of these, 112 statin users were matched to 672 nonusers. Among matched pairs, statin users were not at significantly increased risk (odds ratio: 1.239; 95% confidence interval: 0.768, 1.999) for musculoskeletal conditions. Likewise, there was no observed significant association between specific musculoskeletal disease diagnosis groups and statin use. CONCLUSIONS: In this aviator population, there was not an increased overall likelihood of musculoskeletal conditions for statin users relative to propensity score-matched nonusers. A well-designed prospective cohort analysis or clinical trial is needed to ascertain possible adverse effects of statins on performance in the aviation environment.Tvaryanas AP, Wagner JH, Maupin GM. Statins and musculoskeletal conditions in U.S. Air Force active duty aviators. Aerosp Med Hum Perform. 2018; 89(5):421-427.

The Commander's Wellness Program: Assessing the Association Between Health Measures and Physical Fitness Assessment Scores, Fitness Assessment Exemptions, and Duration of Limited Duty.

INTRODUCTION: Air Force Medical Service health promotions staff have identified a set of evidenced-based interventions targeting tobacco use, sleep habits, obesity/healthy weight, and physical activity that could be integrated, packaged, and deployed as a Commander's Wellness Program. The premise of the program is that improvements in the aforementioned aspects of the health of unit members will directly benefit commanders in terms of members' fitness assessment scores and the duration of periods of limited duty. The purpose of this study is to validate the Commander's Wellness Program assumption that body mass index (BMI), physical activity habits, tobacco use, sleep, and nutritional habits are associated with physical fitness assessment scores, fitness assessment exemptions, and aggregate days of limited duty in the population of active duty U.S. Air Force personnel. METHODS: This study used a cross-sectional analysis of active duty U.S. Air Force personnel with an Air Force Web-based Health Assessment and fitness assessment data during fiscal year 2013. Predictor variables included age, BMI, gender, physical activity level (moderate physical activity, vigorous activity, and muscle activity), tobacco use, sleep, and dietary habits (consumption of a variety of foods, daily servings of fruits and vegetables, consumption of high-fiber foods, and consumption of high-fat foods). Nonparametric methods were used for the exploratory analysis and parametric methods were used for model building and statistical inference. RESULTS: The study population comprised 221,239 participants. Increasing BMI and tobacco use were negatively associated with the outcome of composite fitness score. Increasing BMI and tobacco use and decreasing sleep were associated with an increased likelihood for the outcome of fitness assessment exemption status. Increasing BMI and tobacco use and decreasing composite fitness score and sleep were associated with an increased likelihood for the outcome of limited duty status, whereas increasing BMI and decreasing sleep were associated with the outcome of increased aggregate days of limited duty. The observed associations were in the expected direction and the effect sizes were modest. Physical activity habits and nutritional habits were not observed to be associated with any of the outcome measures. CONCLUSIONS: The Commander's Wellness Program should be scoped to those interventions targeting BMI, composite fitness score, sleep, and tobacco use. Although neither self-reported physical activity nor nutritional habits were associated with the outcomes, it is still worthwhile to include related interventions in the Commander's Wellness Program because of the finding in other studies of a consistent association between the overall number of health risks and productivity outcomes.

Assessment of Deployment-Related Exposures on Risk of Incident Mental Health Diagnoses Among Air Force Medical Service Personnel: Nested Case-Control Study.

Background: Recent military conflicts in Iraq (Operation Iraqi Freedom), Afghanistan (Operation Enduring Freedom), and elsewhere have been associated with psychological impacts among military personnel. However, relatively little is known about the relationship between those conflicts and psychological health of military health care professionals. Previous work has shown certain demographic factors associated with diagnosed mental health conditions after deployment. However, unique exposures in the deployed environment may be present that are also associated. Understanding the relationship between the demographic factors, exposures, and post-deployment mental health (PDMH) conditions has not been investigated. The purpose of this study was to determine the association between occupational and/or environmental exposures and incident PDMH conditions in a defined population of United States Air Force health care personnel returning from the deployed environment (i.e., deployment-related exposures). Methods: A nested case-control study compared cohort members with (N = 4,114) and without (N = 14,073) a PDMH condition in terms of deployment-related occupational and/or environmental exposures. PDMH conditions were identified using the electronic health record and exposures were determined using post-deployment health assessments. Demographic-adjusted multivariable logistic regression models were used to compute odds ratios (ORs). Results: The final regression model comprised five exposure and 12 demographic variables. Reported exposures were not strongly associated with incident PDMH conditions (OR ranged from 1.22 to 1.38) and were lower than some demographic factors. Demographic characteristics with relatively large effect sizes (ORs less than 0.5 or greater than 1.5) included the protective factors of Air Force Guardsman (OR: 0.45), reservists (OR: 0.34), and surgeons (OR: 0.32), as well as the risk factor of nurses (OR: 1.51). All model parameters had a p-value less than 0.0001 and the area under the receiver operating characteristic curve was 0.668. Conclusions: Given the low area under the receiver operating characteristic, the final statistical model had only marginal performance in its ability to correctly identify cases. Thus, other factors should be studied to identify additional predictors for PDMH conditions.

Risk Factors for Hearing Decrement Among U.S. Air Force Aviation-Related Personnel.

INTRODUCTION: The purpose of this study was to analyze historical hearing sensitivity data to determine factors associated with an occupationally significant change in hearing sensitivity in U.S. Air Force aviation-related personnel. METHODS: This study was a longitudinal, retrospective cohort analysis of audiogram records for Air Force aviation-related personnel on active duty during calendar year 2013 without a diagnosis of non-noise-related hearing loss. The outcomes of interest were raw change in hearing sensitivity from initial baseline to 2013 audiogram and initial occurrence of a significant threshold shift (STS) and non-H1 audiogram profile. Potential predictor variables included age and elapsed time in cohort for each audiogram, gender, and Air Force Specialty Code. Random forest analyses conducted on a learning sample were used to identify relevant predictor variables. Mixed effects models were fitted to a separate validation sample to make statistical inferences. RESULTS: The final dataset included 167,253 nonbaseline audiograms on 10,567 participants. Only the interaction between time since baseline audiogram and age was significantly associated with raw change in hearing sensitivity by STS metric. None of the potential predictors were associated with the likelihood for an STS. Time since baseline audiogram, age, and their interaction were significantly associated with the likelihood for a non-HI hearing profile. DISCUSSION: In this study population, age and elapsed time since baseline audiogram were modestly associated with decreased hearing sensitivity and increased likelihood for a non-H1 hearing profile. Aircraft type, as determined from Air Force Specialty Code, was not associated with changes in hearing sensitivity by STS metric.Greenwell BM, Tvaryanas AP, Maupin GM. Risk factors for hearing decrement among U.S. Air Force aviation-related personnel. Aerosp Med Hum Perform. 2018; 89(2):80-86.

Health- and Performance-Related Outcomes in Air Force Medical Service Personnel with a Post-Deployment Mental Health Condition.

Background: This study examined associations between incident post-deployment mental health (PDMH) conditions and health- and performance-related outcomes in the population of Air Force Medical Service personnel on active duty between 2003 and 2013 who had at least one deployment. Methods: Using a posttest-only with nonequivalent groups design, the study cohort was divided into two groups based on the occurrence of an incident PDMH condition, and the groups were then compared in terms of the following health- and performance-related outcomes: health care and pharmaceutical utilization, duty and mobility restrictions, and physical fitness assessment exemptions and composite fitness score. Archival data were extracted from existing databases and associations were assessed using both parametric and nonparametric approaches. Results: The cohort comprised 12,216 participants, from which subcohorts were drawn to assess specific outcome measures. Participants with an incident PDMH used health care at 1.8 times the rate and were 6.2 times more likely to be classified as a high utilizer of health care as compared with those without a PDMH condition (controls). They were 2.1-103.0 times more likely to be prescribed one of 22 therapeutic classes of medication and were 2.4 times more likely to have polypharmacy than controls. They were 2.5 times more likely to have a duty or mobility restriction, and the ratio of days spent with a restriction to days without a restriction was 1.8 times that of controls. Lastly, they were 2.4 times more likely to have a physical fitness assessment exemption, but there was no significant difference in the likelihood of a composite fitness score of <90 points. Conclusions: The presence of an incident PDMH condition was associated with increased health care and pharmaceutical utilization and decreased occupational performance as assessed in terms of restricted duty status and participation in physical fitness assessments.

Statins and Musculoskeletal Conditions in U.S. Air Force Active Duty Service Members.

BACKGROUND: This study examined the association of statin use and musculoskeletal conditions in statin users and nonusers within the population of U.S. Air Force active duty Service members in the military health care system. METHODS: The study was a retrospective cohort analysis of Service members between 2004 and 2014 as identified from personnel data having physical fitness and cardiac risk data available and who were free of musculoskeletal diagnoses for 6 months before the study period. Based on pharmacy data, participants were divided into two groups: statin users (received a statin for at least 90 days) and nonusers (never received a statin throughout the study period). Using participants' baseline characteristics, a propensity score was generated and used to match statin users to nonusers in a 1:3 ratio. Conditional logistic regression was used to determine the odds ratio (OR) for a musculoskeletal injury. FINDINGS: A total of 123,138 participants met study criteria (592 statin users and 122,546 nonusers). Of these, 516 statin users were propensity score matched to 1,548 nonusers. Among matched pairs, statin users had a higher OR (OR: 1.369; 95% confidence interval [CI]: 1.166-1.606) for musculoskeletal conditions. This association was driven by a higher frequency of back problems in statin users relative to nonusers. The number needed to be exposed for one additional person to be harmed was 20.104 (95% CI: 10.326-232.711). DISCUSSION: Statin use was associated with an increased likelihood of musculoskeletal conditions in the population of U.S. Air Force active duty Service members. Further investigations should evaluate the contribution of duty-related physical requirements as well as the duration of musculoskeletal condition-associated duty limitations.

Statin Therapy in Low-Risk Air Force Aviators with Isolated Hypercholesterolemia.

INTRODUCTION: This study evaluated the use of statin therapy in U.S. Air Force (USAF) aviators with isolated hypercholesterolemia in terms of compliance with clinical practice guidelines (CPGs) and effectiveness in reducing low-density lipoprotein cholesterol (LDL-C) and coronary heart disease (CHD) risk. METHODS: This was a mixed design, 8-yr retrospective study that included 8185 participants with isolated hypercholesterolemia, of which 1458 (17.81%) were prescribed statin monotherapy. RESULTS: Overall agreement between CPG recommendations and patient-clinician decision makers was 0.920 (95% confidence interval: 0.955, 0.959) and 0.891 (95% confidence interval: 0.843, 0.851) per 2002 and 2013 CPGs, respectively. Overall agreement was primarily driven by the negative proportion of specific agreement; positive agreement was moderate for the 2002 CPG and poor for the 2013 CPG. LDL-C levels marginally decreased for all participants except non-CPG-recommended statin users per the 2002 CPG. CHD risk was minimally reduced for all participants per the 2002 CPG with the exception of CPG-recommended statin users, for whom risk increased; CHD risk decreased for CPG-recommended statin users, but increased for non-CPG-recommended statin users per the 2013 CPG. No one statin medication was found to be more clinically effective in reducing LDL-C or CHD risk, regardless of dose intensity. CONCLUSIONS: Aerospace medicine practitioners are following CPG recommendations for statin therapy. Statins provided minimal benefit, however, and CPG recommendations proved irrelevant in reducing LDL-C and CHD risk in this population of Air Force aviators. This result is attributable, in part, to the young age of the study cohort and the short follow-up period.Tvaryanas AP, Mahaney HJ, Schroeder VM, Maupin GM. Statin therapy in low-risk air force aviators with isolated hypercholesterolemia. Aerosp Med Hum Perform. 2017; 88(8):752-759.

Risk Factors for Incident Postdeployment Mental Health Conditions Among U.S. Air Force Medical Service Personnel.

The prevalence of postdeployment mental health (PDMH) conditions in military health care personnel appears to be on par with that of other military personnel. However, there is no comprehensive analysis of incident PDMH conditions within the overall population of U.S. Air Force Medical Service personnel. This study explored the epidemiology of incident PDMH conditions among Air Force Medical Service personnel returning from deployment. A cohort survival analysis was conducted of 24,409 subjects without preexisting mental health conditions and at least one deployment during 2003-2013. Electronic health record data were used to ascertain the diagnosis of a PDMH condition. The primary outcome measure was an incident PDMH condition defined as a mental health diagnosis on at least two separate clinical encounters. The incidence of PDMH conditions was 59.74 per 1,000 person-years. Adjustment, anxiety, mood, sleep, and post-traumatic stress disorders accounted for 78% diagnoses. Protective factors included officer, surgeon, specific enlisted career fields, Air National Guard or Air Force Reserve, and multiple deployments. Risk factors included nurse, other specific enlisted career fields, female, and unmarried with dependents. Most subjects (73%) were diagnosed within the standard 30-month surveillance time period; median time to diagnosis was 13 months.

A 10-Year Cross-Sectional Analysis of Air Force Flight and Operational Medicine Clinic Health Care Services.

OBJECTIVES: This study described the patient population and the health care services delivered in the Air Force Flight and Operational Medicine Clinics (FOMCs) over the past 10 years. METHODS: A cross-sectional analysis was performed on the retrospective cohort of patients who received care at a FOMC from 2003 to 2012. RESULTS: A total of 714,157 individuals, generating 4,829,626 encounters, were included in the cohort. They were predominately male service members under the age of 41. One-fifth of individuals were retirees and family members, with one-third being in the pediatric age range. The cohort accessed health care services for three primary reasons: health examinations (28%), occupational dispositions (18%), and primary care (54%). When primary care was sought, the predominate health conditions were upper respiratory infections, back problems, and nontraumatic joint disorders. When services and procedures were a component of the care, they were predominately associated with health examinations involving ophthalmologic, auditory, and cardiac screening tests. Individuals accessing the FOMCs had relatively low need for access to health care services, requiring a median of two annual encounters. CONCLUSIONS: This study provided insight into the health care delivered in FOMCs and establishes a foundation for future planning and management of FOMC health care delivery.

Assessment of Deployment-Related Exposures on Risk of Incident Mental Health Diagnoses Among Air Force Critical Care Providers: Nested Case-Control Study.

OBJECTIVES: The purpose of this study was to determine the association between deployment-related occupational/environmental exposures and incident postdeployment mental health (PDMH) conditions in a defined population of military health care professionals working in the deployed critical care environment. METHODS: A nested case-control study compared cohort members with a PDMH condition (cases, N = 146) with those without a PDMH condition (controls, N = 800) in terms of deployment-related exposures as ascertained using Postdeployment Health Assessment DD 2796 questionnaire data. Multivariable logistic regression models were used to compute odds ratios. RESULTS: Nonphysician career fields (i.e., nurses and medical technicians), exposure to dead bodies or people killed/wounded, history of a vehicular accident/crash, exposure to sand/dust, exposure to lasers, and use of mission-oriented protective posture (MOPP) overgarments were associated with increased likelihood for a PDMH condition. The infrequent exposures (i.e., vehicular accident/crash, lasers, and MOPP overgarments) were the exposures most strongly associated with subsequent PDHM conditions. CONCLUSIONS: For military health care providers returning from the deployed environment, several exposures are useful for predicting those at increased risk for a PDMH condition. However, there are likely many other important risk factors beyond those captured on the DD 2796 questionnaire.

Investigation of Self-Reported Musculoskeletal Injuries on Post-Deployment Health Assessment Forms for Aeromedical Evacuation Personnel.

Musculoskeletal injuries (MSIs) are a concern for the military community because of medical expenses, possible disability, and separation from the military. This study investigated the prevalence of MSIs in deployed aeromedical evacuation (AE) populations reported on Post-Deployment Health Assessment (PDHA) forms. A secondary aim was to examine the relationship between the occurrence of self-reported MSIs on PDHAs and a subsequent medical diagnosis. Flight nurses (Air Force Specialty Code [AFSC] 46F) and AE technicians (AETs) (AFSC 4N0 with a flight duty badge) who completed a PDHA during 2008-2010 were investigated. Data from the test population were compared with a control group of deployed ground-based counterparts. During this time period, 1,366 and 1,959 PDHAs were completed by the AE nursing and AET groups, respectively. At least 1 MSI was reported by 18% of AE nurse and 19% of AET compared with 23% of non-AE nurse and 25% of non-AET PDHAs. Of these individuals with reported MSIs, 35% and 44% of AE nurse and AET PDHAs, respectively, had a diagnosis matching their MSIs. Identifying the prevalence of MSIs in the unique AE environment can lead to the development of preventative and ergonomic solutions, minimizing the risk of MSIs and improving mission success.

Records review of musculoskeletal injuries in aeromedical evacuation personnel.

BACKGROUND: Aeromedical evacuation providers care for patients during air transport. By applying standard medical practices, oftentimes developed for ground care, these practitioners perform their mission duties under additional physical stress in this unique medical environment. Awkward postures and excessive forces are common occurrences among personnel operating in this domain. Additionally, anecdotal reports highlight the risk of developing musculoskeletal injuries for these providers. Currently, there is limited research focusing on musculoskeletal injuries in aeromedical evacuation providers. PURPOSE: To determine the prevalence of musculoskeletal injuries and associated symptoms in aeromedical evacuation providers to understand the risk and burden of these injuries to military personnel. METHODS: This study utilized a retrospective review of military medical records containing ICD-9 codes to investigate the incidence of musculoskeletal injuries within flight nurses and medical technicians compared to their non-flying counterparts from 2006 through 2011. Data were analyzed from 2013 through 2014. RESULTS: Although musculoskeletal injuries were identified within the test populations, results showed fewer injuries for aeromedical evacuation populations compared to non-aeromedical evacuation counterparts. CONCLUSIONS: One contributing factor may be a potential under-reporting of musculoskeletal injuries resulting from the fear of being placed on limited flying status. As flyers, aeromedical evacuation personnel must undergo yearly medical examinations and complete training courses that emphasize proper lifting techniques and physical requirements necessary for the safe and efficient transport of patients on various platforms. These additional requirements may create a healthy worker effect, likely contributing to lower musculoskeletal injuries.

Risk of incident mental health conditions among critical care air transport team members.

BACKGROUND: This study investigated whether Critical Care Air Transport Team (CCATT) members are at increased risk for incident post-deployment mental health conditions. METHODS: We conducted a retrospective cohort study of 604 U.S. Air Force medical personnel without preexisting mental health conditions who had at least one deployment as a CCATT member during 2003-2012 as compared to a control group of 604 medical personnel, frequency matched based on job role, with at least one deployment during the same period, but without CCATT experience. Electronic health record data were used to ascertain the diagnosis of a mental health condition. RESULTS: The incidence of post-deployment mental health conditions was 2.1 per 1000 mo for the CCATT group versus 2.2 per 1000 mo for the control group. The six most frequent diagnoses were the same in both groups: adjustment reaction not including posttraumatic stress disorder (PTSD), anxiety, major depressive disorder, specific disorders of sleep of nonorganic origin, PTSD, and depressive disorder not elsewhere classified. Women were at marginally increased risk and nurses and technicians were at twice the risk of physicians. The distribution of the time interval from end of the most recent deployment to diagnosis of incident mental health condition was positively skewed with a median greater than 6 mo. CONCLUSIONS: CCATT members were at no increased risk for incident post-deployment mental health conditions as compared to non-CCATT medical service members. Nearly two-thirds of incident post-deployment mental health conditions were diagnosed outside the standard 6-mo medical surveillance period, a finding warranting further study.

Diagnosis of 2009 pandemic influenza A (pH1N1) and seasonal influenza using rapid influenza antigen tests, San Antonio, Texas, April-June 2009.

Clinicians frequently use influenza rapid antigen tests for diagnostic testing. We tested nasal wash samples from 1 April to 7 June 2009 from 1538 patients using the QuickVue Influenza A+B (Quidel) rapid influenza antigen test and compared the results with real-time reverse transcription polymerase chain reaction (rRT-PCR) assay (gold standard). The prevalence of 2009 pandemic influenza A (pH1N1) was 1.98%, seasonal influenza type A .87%, and seasonal influenza type B 2.07%. The sensitivity and specificity of the rapid test for pH1N1 was 20% (95% CI, 8-39) and 99% (95% CI, 98-99), for seasonal influenza type A 15% (95% CI, 2-45) and 99% (95% CI, 98-99), and for influenza type B was 31% (95% CI, 9-61) and 99% (95% CI, 98-99.7). Rapid influenza antigen tests were of limited use at a time when the prevalence of pH1N1 and seasonal influenza in the United States was low. Clinicians should instead rely on clinical impression and laboratory diagnosis by rRT-PCR.

Automated analysis of two- and three-color fluorescent Elispot (Fluorospot) assays for cytokine secretion.

The Elispot effectively measures the frequencies of cells secreting particular molecules, especially low-frequency cells such as antigen-specific T cells. The Fluorospot assay adapted this analysis to two products per cell, and this has now been extended to three-color measurement of both mouse and human cytokine-secreting cells. Due to the increased data complexity, and particularly the need to define single-, double- and triple-producing cells, it is critical to objectively quantify spot number, size, intensity, and coincidence with other spots. An automated counting program, Exploraspot, was therefore developed to detect and quantify Fluorospots in automated fluorescence microscope images. Morphological parameters, including size, intensity, location, circularity and others are calculated for each spot, exported in FCS format, and further analyzed by gating and graphical display in popular flow cytometry analysis programs. The utility of Exploraspot is demonstrated by identification of single-, double- and triple-secreting T cells; tolerance of variable background fluorescence; and estimation of the numbers of genuine versus random multiple events.

HIV-specific cytotoxic cell frequencies measured directly ex vivo by the Lysispot assay can be higher or lower than the frequencies of IFN-gamma-secreting cells: anti-HIV cytotoxicity is not generally impaired relative to other chronic virus responses.

CD8(+) T cells in HIV-infected patients are believed to contribute to the containment of the virus and the delay of disease progression. However, the frequencies of HIV-specific CD8(+) T cells, as measured by IFN-gamma secretion and tetramer binding, often do not correlate with a delay in disease progression during chronic infection. Using the Lysispot and ELISPOT assays, we measured the frequencies of cytotoxic and IFN-gamma-secreting T cells responding to overlapping peptides from Gag, Nef, Env, and Pol consensus HIV-1 clade B sequences. PBMC from the majority of HIV-infected subjects have significant frequencies of HIV-specific cells that killed targets within 5 h directly ex vivo. The relative frequencies of IFN-gamma-secreting and cytotoxic cells varied markedly between different HIV peptide pools within the same patient, and some T cells lysed targets without secreting IFN-gamma. These results indicate that measurement of IFN-gamma production alone may be insufficient to evaluate the breadth of the HIV-specific T cell response. Also, neither the CTL to IFN-gamma ratios nor the ex vivo CTL frequencies specific for different HIV proteins were consistently lower than responses specific for two other chronic viral infections, human CMV and EBV, within the same subjects. Thus ex vivo cytotoxic T cell frequencies do not provide evidence for a model of "preterminal differentiation" of HIV-specific CD8(+) T cells during chronic HIV infection. Analysis of the frequency of directly cytotoxic HIV-specific T cells may be of considerable value in the assessment of disease progression and the potential efficacy of HIV vaccines.