The effect of transarterial embolization and nephrectomy on acute kidney injury in patients with blunt renal trauma: An American College of Surgeons - Trauma Quality Improvement Program analysis.

INTRODUCTION: Transarterial embolization (TAE) or nephrectomy for patients with blunt renal trauma might result in acute kidney injury (AKI). Thus, we analyzed the American College of Surgeons - Trauma Quality Improvement Program (TQIP) to validate this. We hypothesized that nephrectomy, and not TAE, would be a risk factor for AKI in patients with blunt renal trauma. MATERIAL AND METHODS: Adult patients with blunt injuries from the TQIP between 2017 and 2019 were eligible for inclusion. The patients were divided into three treatment groups: conservative treatment, TAE, and nephrectomy. Multivariable logistic regression was used to clarify the AKI predictors. RESULTS: The study included 12,843 patients, wherein 12,373 (96.3 %), 229 (1.8 %), and 241 (1.9 %) patients were in the conservative, TAE, and nephrectomy groups, respectively. A total of 269 (2.2 %), 20 (8.7 %), and 29 (12.0 %) patients had AKI in the three groups, respectively. Both TAE (odds ratio [OR], 2.367; 95 % confidence interval [CI], 1.372-3.900; p = 0.001) and Nephrectomy (OR, 2.745; 95 % CI, 1.629-4.528; p < 0.001) were a statistically significant predictor for AKI in the multivariable logistic regression. CONCLUSIONS: TAE and nephrectomy were statistically associated with AKI in patients with blunt renal trauma. This result differs from our previous research findings that nephrectomy, but not TAE, was a risk factor for AKI in patients with blunt renal trauma. Further prospective and well-designed research may be needed.

Feasibility of non-operative management for patients sustained blunt splenic traumas with concomitant aortic injuries.

PURPOSE: This study aimed to elucidate the treatment approach for blunt splenic injuries concurrently involving the aorta. We hypothesized that non-operative management failure rates would be higher in such cases, necessitating increased hemorrhage control surgeries. METHODS: Data from the Trauma Quality Improvement Program spanning 2017 to 2019 were utilized. All patients with blunt splenic trauma were considered for inclusion. We conducted comparisons between blunt splenic trauma patients with and without thoracic or abdominal aortic injuries to identify any potential disparities in treatment. RESULTS: Among the 32,051 patients with blunt splenic injuries during the study period, 752 (2.3%) sustained concurrent aortic injuries. Following 2:1 propensity score matching, it was determined that the presence of aortic injuries did not significantly affect the utilization of splenic transarterial angioembolization (TAE) (7.2% vs. 8.7%, p = 0.243) or the necessity for splenectomy or splenorrhaphy (15.3% vs. 15.7%, p = 0.853). Moreover, aortic injuries were not a significant factor contributing to TAE failure, regardless of the location or severity of the injury. Patients with simultaneous splenic and aortic injuries required more red blood cell transfusion within first 4 hours (0 ml [0, 900] vs. 0 ml [0, 650], p = 0.001) and exhibited a higher mortality rate (10.6% vs. 7.9%, p = 0.038). CONCLUSION: This study demonstrated that patients with concurrent aortic and splenic injuries presented with more severe conditions, higher mortality rates, and extended hospital stays. The presence of aortic injuries did not substantially influence the utilization of TAE or the necessity for splenectomy or splenorrhaphy. Patients of this type can be managed in accordance with current treatment guidelines. Nonetheless, given their less favorable prognosis, they necessitate prompt and proactive intervention.

Opposite effects of Covid-19 infection on pitchers and batters: a retrospective study on Chinese Professional Baseball League players.

BACKGROUND: The influence of COVID-19 infection on elite athletes remains largely unknown, especially on baseball players. The goal of this study is to examine the actual performance of infected elite baseball players from the Chinese Professional Baseball League (CPBL) from a sabermetric point of view. METHODS: This was a retrospective observational cohort study. CPBL players who were infected with COVID-19 from April 27th to May 31st, 2022, were eligible for this study. The performance of study participants before and after COVID-19 infection was compared, and statistics from the batters and pitchers were analyzed separately. RESULTS: During the study interval, 56 players were infected with COVID-19, including 35 batters and 21 pitchers. After excluding injured players and players with inadequate playing opportunities, 23 batters and 12 pitchers were enrolled. For batters, there were no significant differences before and after COVID-19 infection. However, batters older than 28 years of age showed a decline in slugging percentage (0.372 vs. 0.292, P=0.049). Analysis of pitchers revealed significantly boosted fastball velocity after COVID-19 infection (142.10 km/h vs. 142.82 km/h, P=0.028) and improved strikeouts per nine innings (6.89 vs. 8.56, P=0.021). CONCLUSIONS: COVID-19 might have a potential influence on professional baseball players. For batters, veteran players more than 28 years of age were more likely to be negatively affected by COVID-19, whereas the effect of COVID-19 on pitchers was generally positive, with significantly improved fastball velocity and K/9 numbers.

Long-term survival after major trauma: a retrospective nationwide cohort study from the National Health Insurance Research Database.

BACKGROUND: Most trauma-related studies are focused on short-term survival and complications within the index admission, and the long-term outcomes beyond discharge are mainly unknown. The purpose of this study was to analyze the data from the National Health Insurance Research Database (NHIRD) and to assess the long-term survival of major trauma patients after being discharged from the index admission. MATERIAL AND METHODS: This retrospective, observational study included all patients with major trauma (injury severity score ≥16) in Taiwan from 2003 to 2007, and a 10-year follow-up was conducted on this cohort. Patients aged 18-70 who survived the index admission were enrolled. Patients who survived less than one year after discharge (short survival, SS) and those who survived for more than one year (long survival, LS) were compared. Variables, including preexisting factors, injury types, and short-term outcomes and complications, were analyzed, and the 10-year Kaplan-Meier survival analysis was conducted. RESULTS: In our study, 9896 patients were included, with 2736 in the SS group and 7160 in the LS group. Age, sex, comorbidities, low income, cardiopulmonary resuscitation event, prolonged mechanical ventilation, prolonged ICU length of stay (LOS), and prolonged hospital LOS were identified as the independent risk factors of SS. The 10-year cumulative survival for major trauma patients was 63.71%, and the most mortality (27.64%) occurred within the first year after discharge. CONCLUSION: 27.64% of patients would die one year after being discharged from major trauma. Major trauma patients who survived the index admission still had significantly worse long-term survival than the general population, but the curve flattened and resembled the general population after one year.

Accelerated fixation is associated with fewer pulmonary embolism in patients with isolated and unilateral femoral shaft fractures: A TQIP analysis.

INTRODUCTION: The optimal time to intramedullary internal fixation for patients with isolated and unilateral femoral shaft fractures was investigated by the American College of Surgeons-Trauma Quality Improvement Program (ACS-TQIP). MATERIAL AND METHODS: Adult patients from the TQIP between 2017 and 2019 were eligible for inclusion. The associations between time to fixation and target outcomes (pulmonary embolism [PE], deep vein thrombosis [DVT], acute respiratory distress syndrome [ARDS], and mortality) were assessed. Maximization of the sum of sensitivity and specificity was used to determine the optimal cut point. The patients were divided into three groups according to different time to fixation intervals. A multinomial propensity scores weighting using generalized boosted models was performed for all unbiased pre-treatment factors between the groups. Multivariate logistic regression was used to clarify the outcomes predictors. RESULTS: The univariate and multivariate analysis before weighting showed that only PE was significantly associated with time to fixation (odds ratio [OR], 1.05; 95% confidence interval [CI], 1.01-1.09; p = 0.012). The optimal cut point of time to fixation was 13.88 h. The patients were divided into accelerated (≤ 13.88 h), standard (> 13.88 and ≤ 24 h), and delayed (> 24 and < 36 h) groups. After weighting for all unbiased pre-treatment factors between the groups, multivariate logistic regression showed that standard group significantly increased the risk of PE compared with accelerated group (OR, 4.436; 95% CI, 1.844-10.672; p = 0.001). CONCLUSION: Accelerated intramedullary internal fixation within 13.88 h was associated with a significantly decreased risk of PE compared with standard fixation in patients with isolated and unilateral femoral shaft fractures without additional mortality risks.

Effect of zinc supplement on patients with trauma: A systematic review and meta-analysis.

AIMS: This study aimed to assess the effect of zinc supplementation, with or without other antioxidants and trace elements, on clinical outcomes in patients with trauma. METHODS: A systematic review was conducted for adult patients with acute trauma who had been admitted to the hospital. Those who sustained burn injuries were excluded. Studies in PubMed, Web of Science, and Embase from 1990 to 2022 regarding the additional nutrition supplementation of zinc to patients, either in a single-agent or combined regimen, were included. Comparisons were made between the zinc supplement group and those who received a placebo or regular treatment. RESULTS: The primary outcomes of the study were mortality rate, length of hospital stay, and incidence of pneumonia. Seven studies qualified for the meta-analysis. Of the 594 patients eligible for analysis, 290 and 304 were in the zinc supplementation and control groups, respectively. The meta-analysis revealed that zinc supplementation was associated with a lower risk of pneumonia in patients with acute trauma than in the control group (odds ratio [OR], 0.506; 95% CI = 0.292-0.877; P = 0.015; heterogeneity, I2 = 12.7%). Zinc supplementation did not influence the mortality rate (OR, 0.755; 95% CI = 0.492-1.16; P = 0.612; heterogeneity, I2 = 0%) or the length of hospital stay (standard difference in means, -0.24; 95% CI = -0.544 to 0.063; P = 0.121; heterogeneity, I2 = 45.0%). CONCLUSION: Zinc supplementation, with or without other antioxidants and trace elements, in patients with trauma was associated with a lower incidence of pneumonia.

Taiwan cobra envenoming: serum venom concentration before and after specific treatment and relationship with debridement of necrotic wound tissue.

Background: Bivalent freeze-dried neurotoxic (FN) antivenom has been the primary treatment since the 1980s for Taiwan cobra (Naja atra) envenomation in Taiwan. However, envenomation-related wound necrosis is a significant problem after cobra snakebites. In the present study, we analyzed the changes in serum venom concentration before and after antivenom administration to discover their clinical implications and the surgical treatment options for wound necrosis. Methods: The patients were divided into limb swelling and wound necrosis groups. The clinical outcome was that swelling started to subside 12 hours after antivenom treatment in the first group. Serum venom concentrations before and after using antivenoms were measured to assess the antivenom's ability to neutralize the circulating cobra venom. The venom levels in wound wet dressing gauzes, blister fluids, and debrided tissues were also investigated to determine their clinical significance. We also observed the evolutional changes of wound necrosis and chose a better wound debridement timing. Results: We prospectively enrolled 15 Taiwan cobra snakebite patients. Males accounted for most of this study population (n = 11, 73%). The wound necrosis group received more antivenom doses than the limb swelling group (4; IQR:2-6 vs 1; IQR:1-2, p = 0.05), and less records of serum venom concentrations changed before/after antivenom use (p = 0.0079). The necrotic wound site may release venom into circulation and cause more severe envenomation symptoms. Antivenom can efficiently diminish limb swelling in cobra bite patients. However, antivenom cannot reduce wound necrosis. Patients with early debridement of wound necrosis had a better limb outcome, while late or without debridement may have long-term hospital stay and distal limb morbidity. Conclusions: Antivenom can efficiently eliminate the circulating cobra venom in limb swelling patients without wound necrosis. Early debridement of the bite site wound and wet dressing management are suggestions for preventing extended tissue necrosis and hospital stay.

Spleen size greater than 9.76 cm may impact the treatment strategy for blunt splenic injury in adults - A retrospective analysis of experience at a tertiary trauma center in Taiwan.

BACKGROUND/OBJECTIVE: The present study investigated the impact of splenomegaly on the treatment outcomes of blunt splenic injury patients. METHODS: All blunt splenic injury patients were enrolled between 2010 and 2018. The exclusion criteria were age less than 18 years, missing data, and splenectomy performed at another hospital. The patients were divided into two groups based on the presence of splenomegaly, defined as a spleen length over 9.76 cm on axial computed tomography. The primary outcome was the need for hemostatic interventions. RESULTS: A total of 535 patients were included. Patients with splenomegaly had more high-grade splenic injuries (p = 0.007). Hemostatic treatments (p < 0.001) and transarterial embolization (p = 0.003) were more frequently required for patients with splenomegaly. Multivariate analysis showed that male sex (p = 0.023), more packed red blood cell transfusions (p = 0.001), splenomegaly (p = 0.019) and grade 3-5 splenic injury (p < 0.001) were predictors of hemostatic treatment. The failure rate of transarterial embolization was not significantly different between the two groups (p = 0.180). The sensitivity and specificity for splenomegaly in predicting hemostatic procedures were 48.8% and 66.5%, respectively. The positive and negative predictive values were 62.8% and 52.9%, respectively. The overall mortality rate was 3.7%. CONCLUSION: Splenomegaly is an independent predictor for the requirement of hemostatic treatments in blunt splenic injury patients, especially transarterial embolization. Transarterial embolization is as effective for blunt splenic injury patients with splenomegaly as it is for those with a normal spleen.

The Clinical Application of Machine Learning-Based Models for Early Prediction of Hemorrhage in Trauma Intensive Care Units.

Uncontrolled post-traumatic hemorrhage is an important cause of traumatic mortality that can be avoided. This study intends to use machine learning (ML) to build an algorithm based on data collected from an electronic health record (EHR) system to predict the risk of delayed bleeding in trauma patients in the ICU. We enrolled patients with torso trauma in the surgical ICU. Demographic features, clinical presentations, and laboratory data were collected from EHR. The algorithm was designed to predict hemoglobin dropping 6 h before it happened and evaluated the performance with 10-fold cross-validation. We collected 2218 cases from 2008 to 2018 in a trauma center. There were 1036 (46.7%) patients with positive hemorrhage events during their ICU stay. Two machine learning algorithms were used to predict ongoing hemorrhage events. The logistic model tree (LMT) and the random forest algorithm achieved an area under the curve (AUC) of 0.816 and 0.809, respectively. In this study, we presented the ML model using demographics, vital signs, and lab data, promising results in predicting delayed bleeding risk in torso trauma patients. Our study also showed the possibility of an early warning system alerting ICU staff that trauma patients need re-evaluation or further survey.

The Clinical Usefulness of Taiwan Bivalent Freeze-Dried Hemorrhagic Antivenom in Protobothrops mucrosquamatus- and Viridovipera stejnegeri-Envenomed Patients.

Snakebites from Protobothrops mucrosquamatus (Taiwan habus) and Viridovipera stejnegeri (green bamboo vipers) account for the most venomous snakebites in Taiwan. The bivalent freeze-dried hemorrhagic (FH) antivenom is employed to treat these two snakebite patients without a strict clinical trial. We evaluated the clinical usefulness of Taiwan bivalent freeze-dried hemorrhagic (FH) antivenom in Taiwan habu- and green bamboo viper-envenomed patients. We checked ELISA- based serum venom antigen levels before and after FH antivenom to evaluate FH's ability to neutralize patients' serum snake venom and its usefulness in reducing limb swelling after snakebites. Patients who had higher serum venom antigen levels had more severe limb swelling. Of the 33 enrolled patients, most of their snake venom antigen levels were undetected after the appliance of antivenom. Most enrolled patients (25/33) had their limb swelling subside within 12 h after antivenom treatment. The failure to reduce limb swelling was probably due to an inadequate antivenom dose applied in more severely envenomated patients. Our data indicate the feasibility of the FH antivenom in effectively eliminating venom and resolving the affected limb swelling caused by Taiwan habu and green bamboo viper bites.

The Influence of Serious Extracranial Injury on In-Hospital Mortality in Children with Severe Traumatic Brain Injury.

(1) Background: Severe traumatic brain injury (sTBI) is the leading cause of death in children. Serious extracranial injury (SEI) commonly coexists with sTBI after the high impact of trauma. Limited studies evaluate the influence of SEI on the prognosis of pediatric sTBI. We aimed to analyze SEI's clinical characteristics and initial presentations and evaluate if SEI is predictive of higher in-hospital mortality in these sTBI children. (2) Methods: In this 11-year-observational cohort study, a total of 148 severe sTBI children were enrolled. We collected patients' initial data in the emergency department, including gender, age, mechanism of injury, coexisting SEI, motor components of the Glasgow Coma Scale (mGCS) score, body temperature, blood pressure, blood glucose level, initial prothrombin time, and intracranial Rotterdam computed tomography (CT) score of the first brain CT scan, as potential mortality predictors. (3) Results: Compared to sTBI children without SEI, children with SEI were older and more presented with initial hypotension and hypothermia; the initial lab showed more prolonged prothrombin time and a higher in-hospital mortality rate. Multivariate analysis showed that motor components of mGCS, fixed pupil reaction, prolonged prothrombin time, and higher Rotterdam CT score were independent predictors of in-hospital mortality in sTBI children. SEI was not an independent predictor of mortality. (4) Conclusions: sTBI children with SEI had significantly higher in-hospital mortality than those without. SEI was not an independent predictor of mortality in our study. Brain injury intensity and its presentations, including lower mGCS, fixed pupil reaction, higher Rotterdam CT score, and severe injury-induced systemic response, presented as initial prolonged prothrombin time, were independent predictors of in-hospital mortality in these sTBI children.

The role of acute care surgeons in treating rib fractures-a retrospective cohort study from a single level I trauma center.

BACKGROUND: Rib fractures are the most common thoracic injury in patients who sustained blunt trauma, and potentially life-threatening associated injuries are prevalent. Multi-disciplinary work-up is crucial to achieving a comprehensive understanding of these patients. The present study demonstrated the experience of an acute care surgery (ACS) model for rib fracture management from a single level I trauma center over 13 years. METHODS: Data from patients diagnosed with acute rib fractures from January 2008 to December 2020 were collected from the trauma registry of Chang Gung Memorial Hospital (CGMH). Information, including patient age, sex, injury mechanism, Abbreviated Injury Scale (AIS) in different anatomic regions, injury severity score (ISS), index admission department, intensive care unit (ICU) length of stay (LOS), total admission LOS, mortality, and other characteristics of multiple rib fracture, were analyzed. Patients who received surgical stabilization of rib fractures (SSRF) were analyzed separately, and basic demographics and clinical outcomes were compared between acute care and thoracic surgeons. RESULTS: A total of 5103 patients diagnosed with acute rib fracture were admitted via the emergency department (ED) of CGMH in the 13-year study period. The Department of Trauma and Emergency Surgery (TR) received the most patients (70.8%), and the Department of Cardiovascular and Thoracic Surgery (CTS) received only 3.1% of the total patients. SSRF was initiated in 2017, and TR performed fixation for 141 patients, while CTS operated for 16 patients. The basic demographics were similar between the two groups, and no significant differences were noted in the outcomes, including LOS, LCU LOS, length of indwelling chest tube, or complications. There was only one mortality in all SSRF patients, and the patient was from the CTS group. CONCLUSIONS: Acute care surgeons provided good-quality care to rib fracture patients, whether SSRF or non-SSRF. Acute care surgeons also safely performed SSRF. Therefore, we propose that the ACS model may be an option for rib fracture management, depending on the deployment of staff in each institute.

The Impact on the Clinical Prognosis of Low Serum Selenium Level in Patients with Severe Trauma: Systematic Review and Meta-Analysis.

This study was designed to examine the most up-to-date evidence about how low plasma selenium (Se) concentration affects clinical outcomes, such as mortality, infectious complications, and length of ICU or hospital stay, in patients with major trauma. We searched three databases (MEDLINE, EMBASE, and Web of Science) with the following keywords: "injury", "trauma", "selenium", and "trace element". Only records written in English published between 1990 and 2021 were included for analysis. Four studies were eligible for meta-analyses. The results of the meta-analysis showed that a low serum selenium level did not exert a negative effect on the mortality rate (OR 1.07, 95% CI: 0.32, 3.61, p = 0.91, heterogeneity, I2 = 44%). Regarding the incidence of infectious complications, there was no statistically significant deficit after analyses of the four studies (OR 1.61, 95% CI: 0.64, 4.07, p = 0.31, heterogeneity, I2 = 70%). There were no differences in the days spent in the ICU (difference in means (MD) 1.53, 95% CI: -2.15, 5.22, p = 0.41, heterogeneity, I2 = 67%) or the hospital length of stay (MD 6.49, 95% CI: -4.05, 17.02, p = 0.23, heterogeneity, I2 = 58%) in patients with low serum Se concentration. A low serum selenium level after trauma is not uncommon. However, it does not negatively affect mortality and infection rate. It also does not increase the overall length of ICU and hospital stays.

The Impact of Selenium Supplementation on Trauma Patients-Systematic Review and Meta-Analysis.

This study aimed to assess current evidence regarding the effect of selenium (Se) supplementation on the prognosis in patients sustaining trauma. MEDLINE, Embase, and Web of Science databases were searched with the following terms: "trace element", "selenium", "copper", "zinc", "injury", and "trauma". Seven studies were included in the meta-analysis. The pooled results showed that Se supplementation was associated with a lower mortality rate (OR 0.733, 95% CI: 0.586, 0.918, p = 0.007; heterogeneity, I2 = 0%). Regarding the incidence of infectious complications, there was no statistically significant benefit after analyzing the four studies (OR 0.942, 95% CI: 0.695, 1.277, p = 0.702; heterogeneity, I2 = 14.343%). The patients with Se supplementation had a reduced ICU length of stay (standard difference in means (SMD): -0.324, 95% CI: -0.382, -0.265, p < 0.001; heterogeneity, I2 = 0%) and lesser hospital length of stay (SMD: -0.243, 95% CI: -0.474, -0.012, p < 0.001; heterogeneity, I2 = 45.496%). Se supplementation after trauma confers positive effects in decreasing the mortality and length of ICU and hospital stay.

Lymphocyte-to-monocyte ratios predict gastric cancer surgical outcomes.

BACKGROUND: The prognostic role of the preoperative lymphocyte-to-monocyte ratio (LMR) in patients with gastric adenocarcinoma (GC) remains unclear. The aim of this study was to explore the prognostic potential of the preoperative LMR in patients with resectable GC. MATERIALS AND METHODS: The medical records of 926 consecutive patients with resectable GC between 2005 and 2010 were retrospectively reviewed and analyzed. Patients were stratified into two groups based on the preoperative LMR with a cutoff value of 4.8 (group 1: LMR ≤ 4.8; group 2: LMR > 4.8). Clinicopathologic factors potentially affecting patient outcomes were collected prospectively and analyzed. RESULTS: Compared to group 2, in group 1, there was a higher percentage of men, patients aged >48 y, total gastrectomy, tumor size > 4.8 cm, T4 lesions, N3 disease, metastatic tumors, advanced stage, ratio of metastatic to examined lymph nodes > 0.18, R1 resection, and occurrence of vascular or lymphatic invasion. Group 1 also had a higher 30-d surgical mortality rate (groups 1 versus 2 at 2.9% versus 0.5%; P = 0.006) and lower 3-y and 5-y overall survival (53.6% versus 71.9% and 46.4% versus 63.3%, respectively; P < 0.0001). Multivariate analysis showed that preoperative low LMR was an unfavorable prognostic factor for resectable GC. CONCLUSIONS: Patients with lower LMR had more aggressive tumor behavior, higher surgical mortality rates, and worse long-term survival. The preoperative LMR may serve as an independent prognostic factor for prediction of surgical outcomes and for assisting clinicians in determining future treatment plans.

Joystick-controlled video console game practice for developing power wheelchairs users' indoor driving skills.

[Purpose] This study aimed to determine the effectiveness of joystick-controlled video console games in enhancing subjects' ability to control power wheelchairs. [Subjects and Methods] Twenty healthy young adults without prior experience of driving power wheelchairs were recruited. Four commercially available video games were used as training programs to practice joystick control in catching falling objects, crossing a river, tracing the route while floating on a river, and navigating through a garden maze. An indoor power wheelchair driving test, including straight lines, and right and left turns, was completed before and after the video game practice, during which electromyographic signals of the upper limbs were recorded. The paired t-test was used to compare the differences in driving performance and muscle activities before and after the intervention. [Results] Following the video game intervention, participants took significantly less time to complete the course, with less lateral deviation when turning the indoor power wheelchair. However, muscle activation in the upper limbs was not significantly affected. [Conclusion] This study demonstrates the feasibility of using joystick-controlled commercial video games to train individuals in the control of indoor power wheelchairs.

Variation in primary sequence and tandem repeat copy number among i-antigens of Ichthyophthirius multifiliis.

The immobilization antigens (i-antigens) of Ichthyophthirius multifiliis are potential vaccine candidates for the prevention of 'white spot' disease in freshwater fish. These antigens vary with respect to antigenicity and molecular mass, and at least five i-antigen serotypes have been identified among parasite isolates thus far. In previous studies, the gene and corresponding cDNA encoding a approximately 48 kDa i-antigen from parasite isolate G1 (serotype A), had been cloned and sequenced. We now report on the isolation of two new genes, designated IAG52A[G5] and IAG52B[G5], encoding approximately 52/55 kDa i-antigens from a parasite isolate representing a different serotype, namely, D. Based on their deduced sequences, the approximately 52/55 kDa gene products have the same structural features as the 48 kDa protein including hydrophobic N- and C-termini, periodic cysteine residues with the potential for metal binding, and tandemly repetitive amino acid sequence domains that span their length. Nevertheless, the products of these genes vary in their tandem repeat copy number, and share only approximately 50% homology overall. When expressed in heterologous systems, the products of the newly described genes react strongly with monospecific polyclonal antisera against the i-antigens of serotype D and are clearly i-antigens. It would nevertheless appear that mRNA transcripts from the two genes are present at widely different levels within parasites themselves. Analysis at the protein level using 2-D SDS-PAGE would further suggest that multiple i-antigens are expressed within the same serotype at any given time.