Effects of Human Immunodeficiency Virus Status on Trauma Outcomes: A Review of the National Trauma Database

Abstract

Background:

The prevalence of human immunodeficiency virus (HIV) is disproportionately elevated in trauma patients. Although HIV traditionally has been associated with poorer outcomes among the critically ill, recent evidence suggests that the outcomes of surgical patients have improved with the greater use of antiretroviral regimens. The purpose of this study was to utilize the National Trauma Data Bank (NTDB) to examine the impact of HIV on surgical outcomes in a large group of trauma patients.

Methods:

We identified all patients for whom HIV status at time of admission was recorded. Results were stratified by age and Injury Severity Score. Our primary outcome was death. Secondary outcomes were length of hospital stay (LOS), length of intensive care unit (ICU) stay, duration of mechanical ventilation, and complications. Data were analyzed using Student t-tests or chi-square analysis, as appropriate.

Results:

The overall mortality rates were not significantly different in the HIV-positive and HIV-negative groups. Mortality rates remained similar in the two groups even when stratifying by ISS and age, with the exception of those patients who were 65 years or older. The HIV-positive patients had significantly longer LOS (7.6 vs. 5.6 days), shorter duration of mechanical ventilation (6.3 vs. 8.3 days), and no difference in length of ICU stay. The HIV-positive patients were significantly more likely to develop pneumonia, bacteremia, or wound infection.

Conclusions:

These findings are consistent with those of recent smaller studies that demonstrated no significant difference in the mortality rate for patients with HIV. Although mortality rates are similar, HIV-positive patients are more likely to develop certain infectious complications and to require a longer LOS. Infection with HIV remains a major public health issue in the U.S. and internationally, and further research is necessary to explore the relation between HIV status and trauma outcomes, particularly with regard to the possible effects of antiretroviral treatment and individual immune status.

According to the latest update released by the Joint United Nations Programme on HIV/AIDS (UNAIDS) in December 2007, there are 30.6 to 36.1 million people currently living with human immunodeficiency virus/acquired immune deficiency syndrome (HIV/AIDS) worldwide, a number that has been climbing ever since the organization began publishing annual prevalence data in 1998. This disease continues to claim new victims each year, with 2.5 million newly diagnosed cases reported in 2007. More than 6,800 persons become infected with HIV every day, making it one of the largest public health issues in the world. At the same time, recent data suggest that persons infected with HIV are living longer, which accounts for some of the increasing prevalence of the disease [1]. Fewer patients are dying of HIV/AIDS [1,2], which increases the odds that they will die of something else. In fact, the World Health Organization (WHO) projects that the proportion of deaths from non-communicable causes in the developing world will increase to 70% by the year 2030. Trauma death, which already is a leading cause of death in young adults worldwide, is expected to increase by an additional 40% over this same period [2]. These trends mean that surgeons can expect to continue treating a growing number of HIV-positive patients with life-threatening traumatic injuries.

Although specific data differ by country, information collected by the WHO indicates that trauma accounts for a significant portion of deaths in all nations [1]. In the U.S., trauma is the 5^th leading cause of death, and is by far the number one cause for individuals aged 15–44 years [3]. Not only do young adults account for the majority of trauma victims, they also account for the majority of HIV cases. Of the approximately 1.2 million persons in the United States with HIV, more than two-thirds are between the ages of 15 and 44 years [4]. Furthermore, a recent study showed that the prevalence of HIV tends to be slightly higher in the overall trauma population than among the general public. When stratifying by geographic location within the U.S., the prevalence of HIV can climb as high as nearly 5% in certain urban populations [5].

Despite the large number of HIV-positive patients who suffer traumatic injuries, relatively little data exist regarding trauma surgery outcomes in this group. Although HIV traditionally has been associated with poorer outcomes among the critically ill, studies relating to surgical outcomes in HIV-positive patients have been inconsistent. Because of the high prevalence of HIV in severely injured patients, and because of the potential effects of HIV status on a trauma patient's health status, a better understanding of trauma outcomes in HIV-positive patients is needed. The purpose of this study was to utilize the National Trauma Data Bank (NTDB), which contains outcomes data for more than two million U.S. trauma patients, to examine the impact of HIV on surgical outcomes in a large group of severely injured trauma patients nationwide.

Patients and Methods

All data for this study were obtained from the NTDB, version 6.2. The NTDB was established and is maintained by the American College of Surgeons as a public service and includes voluntarily submitted data from more than 400 hospitals throughout the U.S. and Puerto Rico between 1994 and 2005, for a total population of 2.1 million trauma patients.

Individuals were divided into two groups: Those with known HIV infection and those without HIV. The HIV-positive patients were identified by screening for “HIV/AIDS” (ICD-9-CM 079.53) under fieldname “PREXCOMOR” in the database. This information is entered in the NTDB as an established co-morbidity at the time of hospital admission. Demographic data were collected, including age, race, sex, and Injury Severity Score (ISS).

The primary outcome measure was death. In addition to calculating overall mortality rates for the two groups, patients were further stratified by age and ISS. Patients for whom no age was entered were excluded from the subgroup analysis by age. Likewise, patients for whom no ISS was entered were excluded from analysis by injury severity. Secondary outcomes included length of hospital stay (LOS) for all surviving patients, length of intensive care unit (ICU) stay for all surviving patients, duration of mechanical ventilation for all intubated patients, and complications. We examined the outcomes of 20 possible complications, including seven infections (bacteremia, fungemia, pneumonia, empyema, wound infection, abscess, and urinary tract infection). All data were processed using SAS System version 8.2 (SAS Institute, Cary, NC). Results were compared using t-tests for continuous variables and chi-square analysis for categorical variables, with an alpha of 0.05.

Results

Demographics and baseline characteristics

A total of 1,460,201 patients were identified who met our inclusion criteria. Of these, 1,379 (0.09%) had known HIV infection at time of admission. Baseline demographic and injury data are presented in Table 1. The HIV-positive group had a greater percentage of male patients than the HIV-negative group (80% vs. 56%, respectively). The HIV-positive group also had a higher proportion of black patients (47% vs. 17%) and a significantly larger proportion of individuals in the middle-age group, with nearly three quarters of its patients being between 35 and 54 years of age.

Table 1.

Demographics and Baseline Characteristics of Patients ^a

	Human immunodeficiency virus negative (n = 1,460,201) (%)	Human immunodeficiency virus positive (n = 1,379) (%)
Sex
Female	508,889 (35.0)	282 (20.5)
Male	945,994 (65.0)	1,096 (79.5)
Not recorded	5,318 ( 0.4)	1 ( 0.07)
Race
Asian	21,337 ( 1.6)	5 ( 0.4)
Black	228,720 (17.1)	607 (46.9)
Hispanic	137,245 (10.3)	69 ( 5.3)
Native American	8,300 ( 0.6)	3 ( 0.2)
White	904,697 (67.7)	584 (45.1)
Other	36,673 ( 2.7)	27 ( 2.1)
Not recorded	123,229 ( 8.4)	84 ( 6.1)
Age (years)
0–18	277,028 (19.6)	6 ( 0.4)
19–35	428,098 (30.3)	217 (15.9)
36–54	372,782 (26.4)	1,004 (73.5)
55⁺	335,978 (23.8)	139 (10.2)
Not recorded	46,315 ( 3.2)	203 (14.7)
Co-morbidities
None recorded	1,211,015 (82.9)	0^b
1–2	199,705 (13.7)	917 (66.5)
3–4	39,609 ( 2.7)	402 (29.2)
5⁺	9,872 ( 0.7)	60 ( 4.4)
Injury Severity Score
0–15	1,065,962 (78.9)	973 (74.1)
16–25	159,150 (11.8)	182 (13.9)
25⁺	125,493 ( 9.3)	158 ( 9.3)
Not recorded	109,596 ( 7.5)	66 ( 4.8)
Type of trauma
Penetrating	155,593 (10.7)	191 (13.9)
Blunt	1,243,059 (85.1)	1,140 (82.7)
Burn	28,370 ( 1.9)	42 ( 3.0)
Not recorded	33,179 ( 2.3)	6 ( 0.4)

All differences among groups by category are significant at p < 0.001.

By definition, all patients with human immunodeficiency virus had at least one co-morbidity.

By virtue of their HIV-positive status, all individuals in this group had at least one documented co-morbidity at baseline, whereas most (>80%) of patients in the control group had no existing conditions. The HIV-positive individuals were also more likely than controls to have multiple co-morbidities, with more than 30% having three or more (Table 2). The HIV-positive group had a higher proportion of moderately to severely injured patients (ISS > 15) than the control group (25.9% vs. 21.1%). Although the two groups were statistically different with regard to severity of injury, these differences were relatively small, and it is not certain that they represent clinically meaningful differences.

Table 2.

Existing Co-Morbidities

Human immunodeficiency virus negative (n = 560,845)		Human immunodeficiency virus positive (n = 1,005)
Co-morbidity	N (%) of cases	Co-morbidity	N (%) of cases
Hypertension	126,533 (22.6)	Chronic drug abuse	207 (20.6)
Prior cardiac surgery	50,231 ( 9.0)	Chronic alcohol abuse	135 (13.4)
History of psychiatric disorder	43,475 ( 7.8)	Hypertension	135 (13.4)
Chronic alcohol abuse	40,323 ( 7.2)	History of psychiatric disorder	133 (13.2)
Asthma	38,113 ( 6.8)	Seizures	64 ( 6.4)
Non-insulin-dependent diabetes mellitus	31,689 ( 5.7)	Asthma	59 ( 5.9)
Coronary artery disease	27,297 ( 4.9)	Established anemia	28 ( 2.8)
Chronic drug abuse	21,333 ( 3.8)	Non-insulin-dependent diabetes mellitus	27 ( 2.7)
Chronic obstructive pulmonary disease	16,318 ( 2.9)	Chronic obstructive pulmonary disease	25 ( 2.5)
Seizures	16,000 ( 2.9)	End-stage renal disease (dialysis)	22 ( 2.2)
Congestive heart failure	15,770 ( 2.8)	Insulin-dependent diabetes mellitus	21 ( 2.1)
Insulin-dependent diabetes mellitus	14,004 ( 2.5)	Coronary artery disease	15 ( 1.5)
Established anemia	13,665 ( 2.4)	Cirrhosis	15 ( 1.5)
Obesity	12,860 ( 2.3)	Cerebrovascular accident/hemiparesis	11 ( 1.1)
Spinal cord injury	11,089 ( 2.0)	Warfarin therapy	10 ( 1.0)
Warfarin therapy	9,755 ( 1.7)	Congestive heart failure	9 ( 0.9)
Cerebrovascular accident/hemiparesis	8,878 ( 1.6)	Obesity	9 ( 0.9)
Chronic dementia	7,300 ( 1.3)	Known metastases	8 ( 0.9)
Pregnancy	6,946 ( 1.2)	Bilirubin >2 mg/dL	7 ( 0.7)
Alzheimer disease	6,359 ( 1.1)	Chronic dementia	7 ( 0.7)
Chronic pulmonary condition	6,343 ( 1.1)	Hemophilia	7 ( 0.7)
Myocardial infarction	6,239 ( 1.1)	Chronic pulmonary condition	6 ( 0.6)
Rheumatoid arthritis	4,983 ( 0.9)	Prior cardiac surgery	5 ( 0.5)
Parkinson disease	3,437 ( 0.6)	Pregnancy	5 ( 0.5)
Known metastases	2,470 ( 0.4)	Acquired coagulopathy	4 ( 0.4)
Peptic ulcer disease	2,431 ( 0.4)	Peptic ulcer disease	4 ( 0.4)
Cirrhosis	2,229 ( 0.4)	History of pulmonary disease	3 ( 0.3)
End-stage renal disease (dialysis)	2,039 ( 0.4)	Parkinson disease	3 ( 0.3)
Current therapy	1,718 ( 0.3)	Systemic lupus erythematosus	3 ( 0.3)
Organic brain syndrome	1,280 ( 0.2)	Current therapy	3 ( 0.3)
Acquired coagulopathy	1,253 ( 0.2)	Chronic demyelinating disease	2 ( 0.2)
Gastric or esophageal varices	1,079 ( 0.2)	Organic brain syndrome	2 ( 0.2)
Multiple sclerosis	986 ( 0.2)	Routine steroid use	2 ( 0.2)
Inflammatory bowel disease	903 ( 0.2)	Serum creatinine >2 mg/dL	2 ( 0.2)
Pancreatitis	873 ( 0.2)	Spinal cord injury	2 ( 0.2)
Other	4,654 ( 0.8)	Other	5 ( 0.5)

Deaths

The mortality rate was slightly higher for HIV-positive than HIV-negative patients (5.66% vs. 4.66%, respectively); however, this difference did not reach statistical significance (p = 0.842). Because age and injury severity are potentially confounding variables, mortality rates were calculated after stratifying for age and ISS. These data are shown in Tables 3 and 4. No statistical differences in the mortality rate were seen after controlling for these variables, except for those patients who were the oldest. For patients greater than 65 years of age, positive HIV status was associated with a higher mortality rate (15.63% vs. 8.05%; p = 0.0115).

Table 3.

Mortality Rate (%) by Injury Severity Score and Human Immunodeficiency Virus Status ^a

Injury Severity Score	Virus negative (n = 1,286,262)	Virus positive (n = 1,240)	P value
0–15	1.38	1.75	0.322
16–25	6.15	7.69	0.396
≥26	31.78	26.58	0.161
Total	4.76	5.56	0.176

For 173,939 (11.9%) of the HIV-negative patients and 139 (10.1%) of the HIV-positive patients, either Injury Severity Score or survival data were missing.

Table 4.

Mortality Rate (%) by Age and Human Immunodeficiency Virus Status ^a

Age (years)	Virus negative (n = 1,295,525)	Virus positive (n = 1,366)	P value
0–18	2.46	0	0.6974
19–35	4.19	5.77	0.2562
36–50	3.99	4.66	0.3322
51–65	4.91	6.06	0.3860
65⁺	8.05	15.63	0.0150
Total	4.76	5.56	0.1760

For 164,676 (11.3%) of the virus-negative and 13 (0.9%) of the virus-positive patients, either the age or the survival was not known.

Secondary outcomes

There were no statistically significant differences in the duration of mechanical ventilation or length of ICU stay in the two groups. An HIV-positive status was associated with a significantly longer LOS, however (7.6 days vs. 5.6 days; p < 0.0001). These data are depicted in Table 5. Complication rates were low in both groups. Of the 20 complications we examined, statistically significant differences were seen in only four (Table 6). The HIV-positive patients were more likely to suffer from bacteremia, pneumonia, and wound infections than the controls, whereas coagulopathy was less likely to occur in the HIV-positive than the HIV-negative group.

Table 5.

Secondary Outcomes in Trauma Patients According to Human Immunodeficiency Virus Status

	Virus-negative mean (95% CI)	Virus-positive mean (95% CI)	P value
Ventilator days	8.3 (8.2, 8.6)	6.3 (5.2, 7.4)	0.0030
ICU days	5.8 (5.7, 5.8)	6.3 (5.2, 7.4)	0.3170
LOS (days)	5.6 (5.6, 5.6)	7.6 (6.9, 8.3)	<0.0001

CI = confidence interval; ICU = intensive care unit; LOS = length of hospital stay.

Table 6.

Complication Rates (%) According to Human Immunodeficiency Virus Status in Trauma Patients

	Virus negative	Virus positive	P value
Acute respiratory distress syndrome	0.46	0.65	0.3122
Acute myocardial infarction	0.53	0.15	0.0578
Aspiration	0.29	0.22	1.0000
Bacteremia	0.15	0.51	0.0047
Cardiac arrest	0.24	0.07	0.2748
Coagulopathy	0.29	0	0.0393
Compartment syndrome	0.23	0.15	0.8173
Deep venous thrombosis	0.42	0.73	0.0886
Dehiscence	0.04	0.07	0.3874
Fungemia	0.01	0.07	0.1387
Empyema	0.05	0.07	0.5094
Intra-abdominal abscess	0.05	0.07	0.5189
Jaundice	0	0	1.0000
Pancreatitis	0.06	0	1.0000
Pneumonia	1.44	3.19	<0.0001
Pulmonary embolism	0.19	0.15	1.0000
Renal failure	0.30	0.51	0.1387
Skin breakdown	0.26	0.51	0.1000
Urinary tract infection	1.12	1.52	0.1575
Wound infection	0.34	1.02	<0.0001

Accounting for selection bias

One of the greatest limitations of the NTDB is its large potential for selection bias because not all hospitals report information for each category. It is conceivable that failure of some facilities to report complications or co-morbidities might have skewed our results. In order to assess whether this selection bias had any impact on our outcomes, we repeated the above analysis excluding those patients from facilities that did not report any existing conditions or complications. Compared with our initial analysis, which included 700 hospitals with 1,466,887 patients, the exclusion of these non-reporting facilities resulted in a subset of 354 hospitals with an associated 1,158,014 patients. When using this new data set, we found that the results were essentially unchanged. Baseline characteristics were nearly identical, with the HIV-positive group having more black patients (43.8% vs. 15.1%), more patients in the 35–54 age group (73.2% vs. 25.7%), a slightly greater proportion of patients with ISS >15 (23.2% vs. 21.1%), and a slightly higher proportion of penetrating trauma (14.5% vs. 10.5%; p < 0.001 for each comparison). As before, the mortality rate was slightly higher in the HIV-positive group, but the difference did not reach statistical significance (5.26% vs. 4.82%; p = 0.4521). The HIV-positive patients >65 years old still had a higher mortality rate than their HIV-negative counterparts; however, on repeat analysis, this difference did not reach statistical significance (8.53% vs. 15.63%; p = 0.1506). There were no significant differences in the mortality rate when controlling for ISS or age group. As before, HIV-positive patients had significantly higher rates of bacteremia, pneumonia, and wound infection (p < 0.001 for each comparison), with these complications having the same incidence as before.

Discussion

Our finding of no significant difference in mortality rates in HIV-positive and HIV-negative trauma patients is consistent with recent reports from other, smaller studies. Although initially, it was widely believed that HIV seropositivity was associated with a high peri-operative mortality rate, more recent studies for the most part have shown no significant differences. There may be several possible explanations for this paradigm change. The majority of published studies from the 1980s and early 1990s regarding surgical outcomes in HIV-infected individuals were methodologically inconsistent and contained relatively small samples [5 –10]. Some did not distinguish between those patients who were in the more advanced stages of AIDS and otherwise-healthy HIV-positive individuals. Some were merely case reports, which lacked an appropriate control group for comparative analysis. Nevertheless, on the basis of the limited evidence that existed at that time, as well as the biologic plausibility that immunocompromised patients were more likely to suffer high morbidity and mortality rates, it was believed by many that HIV infection was associated with poorer surgical outcomes.

The apparently elevated mortality rate among HIV-positive patients seen in earlier studies may simply have been related to the high proportion of patients in those studies who had already progressed to later stages of the disease. A 1990 analysis of surgical outcomes in HIV-positive hemophiliacs found higher mortality rates only for the small subset of patients who already had AIDS [11]. Subsequent case reports of trauma/burn patients similarly reported that postoperative deaths tended to occur only in severely immunocompromised patients or those in the late stages of AIDS [12,13]. A 1998 literature review by Rose et al. likewise demonstrated that in general, surgical mortality rates were significantly higher only in those patients who possessed stigmata of AIDS preoperatively [14]. In fact, nearly all surgical outcomes studies published since the early 1990s have shown no significant difference in mortality rates for HIV-positive patients [13,15 –19]. We found only one study, published in 2002, that reported a statistically significant relation between HIV status and mortality rate, but regression failed to identify HIV status as an independent predictor of peri-operative death [20]. Unfortunately, the NTDB contains no data on the severity of HIV disease, such as progression to AIDS, viral load, duration of medical management, or CD4⁺ counts—all important variables that clearly affect outcome. This is a regrettable limitation of our study.

Although mortality rates were similar for nearly all the subgroups we examined, our results showed a significantly higher risk of death for HIV-positive patients older than 65 years of age than for similar-age HIV-negative patients. One possible explanation is that this group of patients is more severely injured (possibly as a result of engaging in more high-risk behavior) than their age-matched HIV-negative peers. However, ISS scores and the proportion of penetrating vs. blunt trauma types are similar for the two groups, making this hypothesis unlikely. The more likely explanation for this discrepancy is that older HIV-positive patients have more or more severe co-morbidities than older HIV-negative patients, thus making them more susceptible to post-traumatic complications. This hypothesis is consistent with several previous studies that described a reduced life expectancy for HIV-positive patients in developed countries (by as much as 17 years) compared with the general population, despite the greater availability of antiretroviral medications [21 –24]. One recent study found that mortality rates are similar in HIV-positive and HIV-negative individuals during the first five years of the disease, but that an excess mortality rate persists in those HIV-positive patients who have had the disease longer [25]. The authors hypothesize that this finding may be the result of having started highly-active antiretroviral therapy (HAART) later in the course of disease, toxicity from long-term antiretroviral medication use, development of drug-resistant viral strains, or a higher incidence of co-infections. Each of these factors could reduce the body's immune response to stressors such as trauma.

Although the recent data firmly suggest that mortality rates are not increased in the HIV-positive population, the literature is much more ambiguous with regard to postoperative complications [5]. Again, most of the earlier studies on surgical outcomes and HIV suggested that seropositive individuals suffered from high complication rates [9 –14]. Since then, reports of postoperative infections and other complications have been inconsistent. Numerous studies have reported significantly higher rates of surgical site infections [19], pulmonary complications [17,26], sepsis [16,17], renal complications [17], and other infectious and hematologic complications [20], whereas other studies have shown no difference in complication rates, including those listed [11,13,18,26]. An updated literature review was published in 2006 that echoes this confusion and criticizes many of the studies for their small sample sizes, lack of HIV-negative controls, and failure to stratify patients by immune status or co-morbidities [5]. Their analysis of the conflicting data led the authors to conclude only that “patients with HIV may be expected to have higher rates of infectious and respiratory complications if they have active AIDS … ”

In our analysis of the NTDB, we found similar rates for nearly all complications with the exception of bacteremia, pneumonia, and wound infections. This is compatible with previous studies that suggest a higher risk for infectious and pulmonary complications in HIV-positive patients who are severely immunocompromised. A few authors have attempted to stratify surgical complications by severity of HIV infection in order to determine whether the degree of immune dysfunction (as determined by CD4⁺ counts) is associated with outcomes. Two studies found a higher risk of infectious complications for those whose CD4⁺ counts were <200 cells/mL [19,27], whereas others found no association between CD4⁺ counts and postoperative morbidity [11,18,20,26]. One of the more recent papers found that a high viral load (>300,000/mL copies of viral RNA) was associated significantly with poorer outcomes, regardless of the CD4⁺ count [26]. Taken together, these data suggest that HIV-positive patients who are in the later stages of disease, as evidenced by low CD4⁺ counts, high viral load, or clinical syndrome of AIDS, do indeed have a higher risk of infectious complications. The small, but statistically significant, differences in the rates of bacteremia, pneumonia, and wound infection in our study might reflect a true difference in the postoperative outcomes of seronegative individuals and the small subset of HIV-positive patients with more advanced disease. Unfortunately, the NTDB does not contain data regarding CD4⁺ counts or viral loads, so we are unable to confirm this hypothesis.

In addition to CD4⁺ status, patients' general health at baseline might be an important confounder. An HIV-positive status is associated with a significantly higher incidence of other diseases, including alcoholism, chronic drug use, psychiatric disease, pulmonary disease, and cirrhosis, as well as hematologic, neurologic, and gastrointestinal disorders. These co-morbidities obviously affect the body's nutritional and functional status, which can further compromise these patients' ability to recover from serious injury. However, recent studies have shown that with the more widespread use of HAART, medical and surgical outcomes for HIV-positive patients are improving in a variety of settings. A recent study of general surgery patients, which found similar rates of morbidity and mortality in 332 HIV-positive subjects and their controls, reported that nearly 70% of the HIV-positive individuals were on HAART preoperatively [26]. One explanation for the findings of our study is that greater availability of antiretroviral treatments has helped some individuals with HIV to maintain higher CD4⁺ counts, improved immune status, and better all-around health. As a result of better management of their chronic infection, their physiologic reserves approach those of healthy individuals, thus accounting for similar survival rates after serious injuries.

Unfortunately, the NTDB does not contain any data relating to HAART status or CD4⁺ counts, so we are unable to make a direct association between the use or success of HAART and survival or complication rates. However, we did attempt to characterize patients' underlying health status by comparing the number of co-morbidities at baseline. Our finding that 33.6% of HIV-positive subjects had three or more co-morbidities at the time of admission compared with 3.4% of HIV-negative individuals suggests that a larger proportion of HIV-positive patients indeed are sicker at baseline.

There are several other limitations of this study. For example, it does not account completely for a number of confounders that might affect the mortality rate. Trauma mortality rates increase significantly with age and severity of injury. Our baseline demographics show that the HIV-positive population had a larger proportion of patients between the ages of 35 and 55. Although it has been reported that individuals with HIV are more likely to be involved in high-risk lifestyles such as drug use and criminal activity, which theoretically could result in a greater likelihood of sustaining more life-threatening injuries such as gunshot wounds, we found only slight differences in ISS scores and injury types in the two groups. When stratifying mortality rates by age and injury severity, there were no significant differences, except for those older than 65 years, as discussed above.

Further limitations of our study include possible information and selection bias. Because information is entered in the database on a voluntary basis, presumably by trauma nurses with differing amounts of training and experience, some degree of inconsistency in the way data are categorized and entered is not surprising. Therefore, a certain amount of information bias is expected, although it probably is non-differential, affecting both groups equally. Low complication rates are another example of this bias. Of the more than 700 hospitals included in this study, 262 (37%) reported zero complications, and only 152 (22%) reported overall complication rates >5%. The NTDB significantly underreports trauma complication rates compared with the NSQIP database (which has a more reliable method of data entry) [28]. This discrepancy has been attributed to a lack of infrastructure for reporting complication rates systematically in some of the trauma centers participating in the NTDB registry, thus skewing the overall rates. A recent study of the NTDB by Kardooni et al. found that including complications data from centers that report no complications significantly lowers the overall complication rate, by 12.2%, (p < 0.01) [29]. Including centers that reported only a single complication likewise resulted in significantly lower complication overall rates than might reasonably be expected [29].

The low prevalence of HIV in our sample population is another example of this bias. The proportion of trauma patients we identified in the NTDB who were HIV-positive was 0.09%, which is significantly lower than the known prevalence of this infection in the general population (0.6%)³⁰ and in U.S. trauma populations in particular (as high as 4.3%) [5]. This underreporting may be a result of clerical error, failure of the patient to disclose his/her HIV status to the treating hospital, or the patient's lack of unawareness of his/her HIV status. We attempted to assess any effect of this selection bias on our outcomes by first analyzing the entire NTDB database, and then repeating our analysis using an NTDB subset that excluded “non-reporters” of co-morbidity and complication data. In so doing, we found that our results were essentially unchanged, lending validity to our conclusions.

Despite the NTDB's limitations, the outcomes of this study have several important implications. First, they confirm that, in general, HIV-positive patients do not have a higher risk of death after trauma regardless of injury severity. Previous arguments for less aggressive surgical interventions in this subgroup therefore are unjustified, as these patients can be expected to have the same chance of survival as the general population. Second, we confirm within the trauma population a phenomenon recently reported in the general population, namely that older patients with HIV are at a greater risk for excess mortality rates than younger patients, although the underlying reasons for this discrepancy are not understood completely. Finally, our paper adds weight to the controversy over whether HIV-positive patients truly have a higher risk of postoperative infectious and pulmonary complications. Our highly powered study suggests that HIV-positive individuals are indeed at greater risk for these complications; therefore, a higher level of vigilance and prophylactic measures may be warranted in this group of patients.

In conclusion, this study of more than two million patients nationwide indicates that trauma patients with HIV do not have a higher mortality rate than those who do not have HIV. Furthermore, the incidence of post-traumatic complications is similar in HIV-positive and HIV-negative individuals with the exception of bacteremia, pneumonia, and wound infections, which are more common in the HIV-positive group. It is possible that improvement in the management of HIV with HAART accounts for this apparent improvement in outcomes, although this paper lacks the data to confirm such an association. Further research is necessary to explore the relation between HIV status and trauma mortality rates in the United States.

Author Disclosure Statement

None of the authors has any disclosures to make.

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