Effect of Aspirin Versus Low-Molecular-Weight Heparin Thromboprophylaxis on Medication Satisfaction and Out-of-Pocket Costs: A Secondary Analysis of a Randomized Clinical Trial

BACKGROUND

Current guidelines recommend low-molecular-weight heparin for thromboprophylaxis after orthopaedic trauma. However, recent evidence suggests that aspirin is similar in efficacy and safety. To understand patients' experiences with these medications, we compared patients' satisfaction and out-of-pocket costs after thromboprophylaxis with aspirin versus low-molecular-weight heparin.

METHODS

This study was a secondary analysis of the PREVENTion of CLots in Orthopaedic Trauma (PREVENT CLOT) trial, conducted at 21 trauma centers in the U.S. and Canada. We included adult patients with an operatively treated extremity fracture or a pelvic or acetabular fracture. Patients were randomly assigned to receive 30 mg of low-molecular-weight heparin (enoxaparin) twice daily or 81 mg of aspirin twice daily for thromboprophylaxis. The duration of the thromboprophylaxis, including post-discharge prescription, was based on hospital protocols. The study outcomes included patient satisfaction with and out-of-pocket costs for their thromboprophylactic medication measured on ordinal scales.

RESULTS

The trial enrolled 12,211 patients (mean age and standard deviation [SD], 45 ± 18 years; 62% male), 9725 of whom completed the question regarding their satisfaction with the medication and 6723 of whom reported their out-of-pocket costs. The odds of greater satisfaction were 2.6 times higher for patients assigned to aspirin than those assigned to low-molecular-weight heparin (odds ratio [OR]: 2.59; 95% confidence interval [CI]: 2.39 to 2.80; p < 0.001). Overall, the odds of incurring any out-of-pocket costs for thromboprophylaxis medication were 51% higher for patients assigned to aspirin compared with low-molecular-weight heparin (OR: 1.51; 95% CI: 1.37 to 1.66; p < 0.001). However, patients assigned to aspirin had substantially lower odds of out-of-pocket costs of at least $25 (OR: 0.15; 95% CI: 0.12 to 0.18; p < 0.001).

CONCLUSIONS

Use of aspirin substantially improved patients' satisfaction with their medication after orthopaedic trauma. While aspirin use increased the odds of incurring any out-of-pocket costs, it protected against costs of ≥$25, potentially improving health equity for thromboprophylaxis.

LEVEL OF EVIDENCE

Therapeutic Level II . See Instructions for Authors for a complete description of levels of evidence.

The local and systemic effects of immune function on fracture healing

The immune system plays an integral role in the regulation of cellular processes responsible for fracture healing. Local and systemic influences on fracture healing correlate in many ways with fracture-related outcomes, including soft tissue healing quality and fracture union rates. Impaired soft tissue healing, restricted perfusion of a fracture site, and infection also in turn affect the immune response to fracture injury. Modern techniques used to investigate the relationship between immune system function and fracture healing include precision medicine, using vast quantities of data to interpret broad patterns of inflammatory response. Early data from the PRECISE trial have demonstrated distinct patterns of inflammatory response in polytrauma patients, which thereby directly and indirectly regulate the fracture healing response. The clearly demonstrated linkage between immune function and fracture healing suggests that modulation of immune function has significant potential as a therapeutic target that can be used to enhance fracture healing.

How many sites should an orthopedic trauma prospective multicenter trial have? A marginal analysis of the Major Extremity Trauma Research Consortium completed trials

BACKGROUND

Multicenter trials in orthopedic trauma are costly, yet crucial to advance the science behind clinical care. The number of sites is a key cost determinant. Each site has a fixed overhead cost, so more sites cost more to the study. However, more sites can reduce total costs by shortening the study duration. We propose to determine the optimal number of sites based on known costs and predictable site enrollment.

METHODS

This retrospective marginal analysis utilized administrative and financial data from 12 trials completed by the Major Extremity Trauma Research Consortium. The studies varied in size, design, and clinical focus. Enrollment across the studies ranged from 1054 to 33 patients. Design ranged from an observational study with light data collection to a placebo-controlled, double-blinded, randomized controlled trial. Initial modeling identified the optimal number of sites for each study and sensitivity analyses determined the sensitivity of the model to variation in fixed overhead costs.

RESULTS

No study was optimized in terms of the number of participating sites. Excess sites ranged from 2 to 39. Excess costs associated with extra sites ranged from $17K to $330K with a median excess cost of $96K. Excess costs were, on average, 7% of the total study budget. Sensitivity analyses demonstrated that studies with higher overhead costs require more sites to complete the study as quickly as possible.

CONCLUSIONS

Our data support that this model may be used by clinical researchers to achieve future study goals in a more cost-effective manner.

TRIAL REGISTRATION

Please see Table 1 for individual trial registration numbers and dates of registration.

Aspirin or Low-Molecular-Weight Heparin for Thromboprophylaxis after a Fracture

BACKGROUND

Clinical guidelines recommend low-molecular-weight heparin for thromboprophylaxis in patients with fractures, but trials of its effectiveness as compared with aspirin are lacking.

METHODS

In this pragmatic, multicenter, randomized, noninferiority trial, we enrolled patients 18 years of age or older who had a fracture of an extremity (anywhere from hip to midfoot or shoulder to wrist) that had been treated operatively or who had any pelvic or acetabular fracture. Patients were randomly assigned to receive low-molecular-weight heparin (enoxaparin) at a dose of 30 mg twice daily or aspirin at a dose of 81 mg twice daily while they were in the hospital. After hospital discharge, the patients continued to receive thromboprophylaxis according to the clinical protocols of each hospital. The primary outcome was death from any cause at 90 days. Secondary outcomes were nonfatal pulmonary embolism, deep-vein thrombosis, and bleeding complications.

RESULTS

A total of 12,211 patients were randomly assigned to receive aspirin (6101 patients) or low-molecular-weight heparin (6110 patients). Patients had a mean (±SD) age of 44.6±17.8 years, 0.7% had a history of venous thromboembolism, and 2.5% had a history of cancer. Patients received a mean of 8.8±10.6 in-hospital thromboprophylaxis doses and were prescribed a median 21-day supply of thromboprophylaxis at discharge. Death occurred in 47 patients (0.78%) in the aspirin group and in 45 patients (0.73%) in the low-molecular-weight-heparin group (difference, 0.05 percentage points; 96.2% confidence interval, -0.27 to 0.38; P<0.001 for a noninferiority margin of 0.75 percentage points). Deep-vein thrombosis occurred in 2.51% of patients in the aspirin group and 1.71% in the low-molecular-weight-heparin group (difference, 0.80 percentage points; 95% CI, 0.28 to 1.31). The incidence of pulmonary embolism (1.49% in each group), bleeding complications, and other serious adverse events were similar in the two groups.

CONCLUSIONS

In patients with extremity fractures that had been treated operatively or with any pelvic or acetabular fracture, thromboprophylaxis with aspirin was noninferior to low-molecular-weight heparin in preventing death and was associated with low incidences of deep-vein thrombosis and pulmonary embolism and low 90-day mortality. (Funded by the Patient-Centered Outcomes Research Institute; PREVENT CLOT ClinicalTrials.gov number, NCT02984384.).

Defining Incidence of Acute Compartment Syndrome in the Research Setting: A Proposed Method From the PACS Study

OBJECTIVE

To compare the retrospective decision of an expert panel who assessed likelihood of acute compartment syndrome (ACS) in a patient with a high-risk tibia fracture with decision to perform fasciotomy.

DESIGN

Prospective observational study.

SETTING

Seven Level 1 trauma centers.

PATIENTS/PARTICIPANTS

One hundred eighty-two adults with severe tibia fractures.

MAIN OUTCOME MEASUREMENTS

Diagnostic performance (sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and receiver-operator curve) of an expert panel's assessment of likelihood ACS compared with fasciotomy as the reference diagnostic standard.

SECONDARY OUTCOMES

The interrater reliability of the expert panel as measured by the Krippendorff alpha. Expert panel consensus was determined using the percent of panelists in the majority group of low (expert panel likelihood of ≤0.3), uncertain (0.3-0.7), or high (>0.7) likelihood of ACS.

RESULTS

Comparing fasciotomy (the diagnostic standard) and the expert panel's assessment as the diagnostic classification (test), the expert panel's determination of uncertain or high likelihood of ACS (threshold >0.3) had a sensitivity of 0.90 (0.70, 0.99), specificity of 0.95 (0.90, 0.98), PPV of 0.70 (0.50, 0.86), and NPV of 0.99 (0.95, 1.00). When a threshold of >0.7 was set as a positive diagnosis, the expert panel assessment had a sensitivity of 0.67 (0.43, 0.85), specificity of 0.98 (0.95, 1.00), PPV of 0.82 (0.57, 0.96), and NPV of 0.96 (0.91, 0.98).

CONCLUSION

In our study, the retrospective assessment of an expert panel of the likelihood of ACS has good specificity and excellent NPV for fasciotomy, but only low-to-moderate sensitivity and PPV. The discordance between the expert panel-assessed likelihood of ACS and the decision to perform fasciotomy suggests that concern regarding potential diagnostic bias in studies of ACS is warranted.

LEVEL OF EVIDENCE

Diagnostic Level I. See Instructions for Authors for a complete description of levels of evidence.

Streamlining Trauma Research Evaluation With Advanced Measurement (STREAM) Study: Implementation of the PROMIS Toolbox Within an Orthopaedic Trauma Clinical Trials Consortium

LEVEL OF EVIDENCE

Prognostic Level II.

Patient-Specific Precision Injury Signatures to Optimize Orthopaedic Interventions in Multiply Injured Patients (PRECISE STUDY)

SUMMARY

Optimal timing and procedure selection that define staged treatment strategies can affect outcomes dramatically and remain an area of major debate in the treatment of multiply injured orthopaedic trauma patients. Decisions regarding timing and choice of orthopaedic procedure(s) are currently based on the physiologic condition of the patient, resource availability, and the expected magnitude of the intervention. Surgical decision-making algorithms rarely rely on precision-type data that account for demographics, magnitude of injury, and the physiologic/immunologic response to injury on a patient-specific basis. This study is a multicenter prospective investigation that will work toward developing a precision medicine approach to managing multiply injured patients by incorporating patient-specific indices that quantify (1) mechanical tissue damage volume; (2) cumulative hypoperfusion; (3) immunologic response; and (4) demographics. These indices will formulate a precision injury signature, unique to each patient, which will be explored for correspondence to outcomes and response to surgical interventions. The impact of the timing and magnitude of initial and staged surgical interventions on patient-specific physiologic and immunologic responses will be evaluated and described. The primary goal of the study will be the development of data-driven models that will inform clinical decision-making tools that can be used to predict outcomes and guide intervention decisions.

Cognitive-Behavioral-Based Physical Therapy for Improving Recovery After Traumatic Orthopaedic Lower Extremity Injury (CBPT-Trauma)

SUMMARY

Physical and psychological impairment resulting from traumatic injuries is often significant and affects employment and functional independence. Extremity trauma has been shown to negatively affect long-term self-reported physical function, the ability to work, and participation in recreational activities and contributes to increased rates of anxiety and/or depression. High pain levels early in the recovery process and psychosocial factors play a prominent role in recovery after traumatic lower extremity injury. Cognitive-behavioral therapy pain programs have been shown to mitigate these effects. However, patient access issues related to financial and transportation constraints and the competing demands of treatment focused on the physical sequelae of traumatic injury limit patient participation in this treatment modality. This article describes a telephone-delivered cognitive-behavioral-based physical therapy (CBPT-Trauma) program and design of a multicenter trial to determine its effectiveness after lower extremity trauma. Three hundred twenty-five patients from 7 Level 1 trauma centers were randomized to CBPT-Trauma or an education program after hospital discharge. The primary hypothesis is that compared with patients who receive an education program, patients who receive the CBPT-Trauma program will have improved physical function, pain, and physical and mental health at 12 months after hospital discharge.

Can financial payments incentivize short-term smoking cessation in orthopaedic trauma patients? Evidence from a discrete choice experiment

BACKGROUND

Smoking increases the risk of complications and related costs after an orthopaedic fracture. Research in other populations suggests that a one-time payment may incentivize smoking cessation. However, little is known on fracture patients' willingness to accept financial incentives to stop smoking; and the level of incentive required to motivate smoking cessation in this population. This study aimed to estimate the financial threshold required to motivate fracture patients to stop smoking after injury.

METHODS

This cross-sectional study utilized a discrete choice experiment (DCE) to elicit patient preferences towards financial incentives and reduced complications associated with smoking cessation. We presented participants with 12 hypothetical options with several attributes with varying levels. The respondents' data was used to determine the utility of each attribute level and the relative importance associated with each attribute.

RESULTS

Of the 130 enrolled patients, 79% reported an interest in quitting smoking. We estimated the financial incentive to be of greater relative importance (ri) (45%) than any of the included clinical benefits of smoking cessations (deep infection (ri: 24%), bone healing complications (ri: 19%), and superficial infections (ri: 12%)). A one-time payment of $800 provided the greatest utility to the respondents (0.64, 95% CI: 0.36 to 0.93), surpassing the utility associated with a single $1000 financial incentive (0.36, 95% CI: 0.18 to 0.55).

CONCLUSIONS

Financial incentives may be an effective tool to promote smoking cessation in the orthopaedic trauma population. The findings of this study define optimal payment thresholds for smoking cessation programs.

PREVENTion of CLots in Orthopaedic Trauma (PREVENT CLOT): a randomised pragmatic trial protocol comparing aspirin versus low-molecular-weight heparin for blood clot prevention in orthopaedic trauma patients

INTRODUCTION

Patients who sustain orthopaedic trauma are at an increased risk of venous thromboembolism (VTE), including fatal pulmonary embolism (PE). Current guidelines recommend low-molecular-weight heparin (LMWH) for VTE prophylaxis in orthopaedic trauma patients. However, emerging literature in total joint arthroplasty patients suggests the potential clinical benefits of VTE prophylaxis with aspirin. The primary aim of this trial is to compare aspirin with LMWH as a thromboprophylaxis in fracture patients.

METHODS AND ANALYSIS

PREVENT CLOT is a multicentre, randomised, pragmatic trial that aims to enrol 12 200 adult patients admitted to 1 of 21 participating centres with an operative extremity fracture, or any pelvis or acetabular fracture. The primary outcome is all-cause mortality. We will evaluate non-inferiority by testing whether the intention-to-treat difference in the probability of dying within 90 days of randomisation between aspirin and LMWH is less than our non-inferiority margin of 0.75%. Secondary efficacy outcomes include cause-specific mortality, non-fatal PE and deep vein thrombosis. Safety outcomes include bleeding complications, wound complications and deep surgical site infections.

ETHICS AND DISSEMINATION

The PREVENT CLOT trial has been approved by the ethics board at the coordinating centre (Johns Hopkins Bloomberg School of Public Health) and all participating sites. Recruitment began in April 2017 and will continue through 2021. As both study medications are currently in clinical use for VTE prophylaxis for orthopaedic trauma patients, the findings of this trial can be easily adopted into clinical practice. The results of this large, patient-centred pragmatic trial will help guide treatment choices to prevent VTE in fracture patients.

TRIAL REGISTRATION NUMBER

NCT02984384.

Reducing High-Dose Opioid Prescribing: State-Level Morphine Equivalent Daily Dose Policies, 2007-2017

OBJECTIVE

To describe current state-level policies in the United States, January 1, 2007-June 1, 2017, limiting high morphine equivalent daily dose (MEDD) prescribing.

METHODS

State-level MEDD threshold policies were reviewed using LexisNexis and Westlaw Next for legislative acts and using Google for nonlegislative state-level policies. The websites of each state's Medicaid agency, health department, prescription drug monitoring program, workers' compensation board, medical board, and pharmacy board were reviewed to identify additional policies. The final policy list was checked against existing policy compilations and academic literature and through contact with state health agency representatives. Policies were independently double-coded on the categories: state, agency/organization, policy type, effective date, threshold level, and policy exceptions.

RESULTS

Currently, 22 states have at least one type of MEDD policy, most commonly guidelines (14 states), followed by prior authorizations (four states), rules/regulations (four states), legislative acts (three states), claim denials (two states), and alert systems/automatic patient reports (two states). Thresholds range widely (30-300 mg MEDD), with higher thresholds generally corresponding to more restrictive policies (e.g., claim denial) and lower thresholds corresponding to less restrictive policies (e.g., guidelines). The majority of policies exclude some groups of opioid users, most commonly patients with terminal illnesses or acute pain.

CONCLUSIONS

MEDD policies have gained popularity in recent years, but considerable variation in threshold levels and policy structure point to a lack of consensus. This work provides a foundation for future evaluation of MEDD policies and may inform states considering adopting such policies.

Continuous Near-Infrared Spectroscopy Demonstrates Limitations in Monitoring the Development of Acute Compartment Syndrome in Patients with Leg Injuries

BACKGROUND

We recorded measurements of muscle perfusion using near-infrared spectroscopy (NIRS) and intramuscular pressure (IMP) in a study designed to develop a decision rule for predicting acute compartment syndrome (ACS). The purpose of this study was to report our experience measuring NIRS data in the context of this broader investigation and to explore factors related to variations in data capture.

METHODS

One hundred and eighty-five patients with lower-leg injuries had data consisting of continuous NIRS measurement of the O2 saturation in the anterior compartment of the injured limb and the contralateral (control) limb, and continuous IMP recording in the anterior and deep posterior compartments of the injured leg as part of their participation in an institutional review board-approved multicenter trial. All monitoring was done for a prescribed period of time. For both types of data, the percentage of valid data capture was defined as the ratio of the minutes of observed data points within a physiological range to the total minutes of expected data points. Clinically useful NIRS data required simultaneous data from the injured and control limbs to calculate the ratio. Statistical tests were used to compare the 2 methods as well as factors associated with the percent of valid NIRS data capture.

RESULTS

For the original cohort, clinically useful NIRS data were available a median of 9.1% of the expected time, while IMP data were captured a median of 87.6% of the expected time (p < 0.001). Excluding 46 patients who had erroneous NIRS data recorded, the median percentage was 31.6% for NIRS compared with 87.4% for IMP data (p < 0.00001). Fractures with an associated hematoma were less likely to have valid data points (odds ratio [OR], 0.53; p = 0.04). Gustilo types-I and II open fractures were more likely than Tscherne grades C0 and C1 closed fractures to have valid data points (OR, 1.97; p = 0.03).

CONCLUSIONS

In this study, NIRS data were not collected reliably. In contrast, IMP measurements were collected during >85% of the expected monitoring period. These data raise questions about the utility of current NIRS data capture technology for monitoring oxygenation in patients at risk of ACS.

Predicting Acute Compartment Syndrome (PACS): The Role of Continuous Monitoring

The diagnosis of acute compartment syndrome (ACS) is a common clinical challenge among patients who sustain high-energy orthopaedic trauma, largely because no validated criteria exist to reliably define the presence of the condition. In the absence of validated diagnostic standards, concern for the potential clinical and medicolegal impact of a missed compartment syndrome may result in the potential overuse of fasciotomy in "at-risk" patients. The goal of the Predicting Acute Compartment Syndrome Study was to develop a decision rule for predicting the likelihood of ACS that would reduce unnecessary fasciotomies while guarding against potentially missed ACS. Of particular interest was the utility of early and continuous monitoring of intramuscular pressure and muscle oxygenation using near-infrared spectroscopy in the timely diagnosis of ACS. In this observational study, 191 participants aged 18-60 with high-energy tibia fractures were prospectively enrolled and monitored for up to 72 hours after admission, then followed for 6 months. Treating physicians were blinded to continuous pressure and oxygenation data. An expert panel of 9 orthopaedic surgeons retrospectively assessed the likelihood that each patient developed ACS based on data collected on initial presentation, clinical course, and known functional outcome at 6 months. This retrospectively assigned likelihood is modeled as a function of clinical data typically available within 72 hours of admission together with continuous pressure and oxygenation data. This study will improve our understanding of the natural history of compartment syndrome and examine the utility of early and continuous monitoring of the physiologic status of the injured extremity in the timely diagnosis of ACS.

The impact of trauma-center care on functional outcomes following major lower-limb trauma

BACKGROUND

Although studies have shown that treatment at a trauma center reduces a patient's risk of dying following major trauma, important questions remain as to the effect of trauma centers on functional outcomes, especially among patients who have sustained major lower-limb trauma.

METHODS

Domain-specific scores on the Medical Outcomes Study Short Form Health Survey (SF-36) supplemented by scores on the mobility subscale of the Musculoskeletal Function Assessment (MFA) and the Revised Center for Epidemiologic Studies Depression Scale (CESD-R) were compared among patients treated in eighteen hospitals with a level-I trauma center and fifty-one hospitals without a trauma center. Included in the study were 1389 adults, eighteen to eighty-four years of age, with at least one lower-limb injury with a score of >/=3 points according to the Abbreviated Injury Scale (AIS). To account for the competing risk of death, we estimated the survivors' average causal effect. Estimates were derived for all patients with a lower-limb injury and separately for a subset of patients without associated injuries of the head or spinal cord.

RESULTS

For patients with a lower-limb injury resulting from a high-energy force, care at a trauma center yielded modest but clinically meaningful improvements in physical functioning and overall vitality at one year after the injury. After adjustment for differences in case mix and the competing risk of death, the average differences in the SF-36 physical functioning and vitality scores and the MFA mobility score were 7.82 points (95% confidence interval: 2.65, 12.98), 6.80 points (95% confidence interval: 2.53, 11.07), and 6.31 points (95% confidence interval: 0.25, 12.36), respectively. These results were similar when the analysis was restricted to patients without associated injuries to the head or spine. Treatment at a trauma center resulted in negligible differences in outcome for the subset of patients with injuries resulting from low-energy forces.

CONCLUSIONS

This study provides evidence that patients who sustain high-energy lower-limb trauma benefit from treatment at a level-I trauma center.

A national evaluation of the effect of trauma-center care on mortality

BACKGROUND

Hospitals have difficulty justifying the expense of maintaining trauma centers without strong evidence of their effectiveness. To address this gap, we examined differences in mortality between level 1 trauma centers and hospitals without a trauma center (non-trauma centers).

METHODS

Mortality outcomes were compared among patients treated in 18 hospitals with a level 1 trauma center and 51 hospitals non-trauma centers located in 14 states. Patients 18 to 84 years old with a moderate-to-severe injury were eligible. Complete data were obtained for 1104 patients who died in the hospital and 4087 patients who were discharged alive. We used propensity-score weighting to adjust for observable differences between patients treated at trauma centers and those treated at non-trauma centers.

RESULTS

After adjustment for differences in the case mix, the in-hospital mortality rate was significantly lower at trauma centers than at non-trauma centers (7.6 percent vs. 9.5 percent; relative risk, 0.80; 95 percent confidence interval, 0.66 to 0.98), as was the one-year mortality rate (10.4 percent vs. 13.8 percent; relative risk, 0.75; 95 percent confidence interval, 0.60 to 0.95). The effects of treatment at a trauma center varied according to the severity of injury, with evidence to suggest that differences in mortality rates were primarily confined to patients with more severe injuries.

CONCLUSIONS

Our findings show that the risk of death is significantly lower when care is provided in a trauma center than in a non-trauma center and argue for continued efforts at regionalization.

Beyond the actor's traits: forming impressions of actors, targets, and relationships from social behaviors

Perceivers who observe social behaviors may form impressions not only of actors' traits but also of people as targets and of interpersonal relationships. In Study 1, Ss read about 4 individuals' behaviors under instructions to form actor-, target-, and relationship-based impressions. Ss then read additional behavioral information that they later tried to recall. Ss accurately perceived actor, target, and relationship effects in the presented information, and they better recalled subsequent behaviors that were consistent with all 3 types of impressions. In Study 2, Ss thought of 4 people they knew and judged how much each liked the other 3. These ratings revealed actor, target, and relationship effects as well as individual and dyadic reciprocity. Perceivers can form relatively accurate impressions of people as actors and as targets and accurate impressions of relationships between people, and these impressions influence memory for further behaviors.

Beyond the actor's traits: forming impressions of actors, targets, and relationships from social behaviors

Perceivers who observe social behaviors may form impressions not only of actors' traits but also of people as targets and of interpersonal relationships. In Study 1, Ss read about 4 individuals' behaviors under instructions to form actor-, target-, and relationship-based impressions. Ss then read additional behavioral information that they later tried to recall. Ss accurately perceived actor, target, and relationship effects in the presented information, and they better recalled subsequent behaviors that were consistent with all 3 types of impressions. In Study 2, Ss thought of 4 people they knew and judged how much each liked the other 3. These ratings revealed actor, target, and relationship effects as well as individual and dyadic reciprocity. Perceivers can form relatively accurate impressions of people as actors and as targets and accurate impressions of relationships between people, and these impressions influence memory for further behaviors.

Immunoreactivity in malignant mesotheliomas with antibodies to basement membrane components and their receptors

Ten cases of malignant mesothelioma (MM), as diagnosed by clinical history and light and electron microscopy, were studied with polyclonal antibodies directed against the basement membrane-specific proteins, type IV collagen and laminin, as well as with monoclonal antibodies which recognize two epitopes of the laminin receptor (LR). All formalin-fixed, paraffin-embedded mesothelioma tissues examined demonstrated intracytoplasmic immunoreactivity for the basement membrane proteins. Extracellular staining was minimal, analogous to the staining reactions observed in adenocarcinomas of the breast and lung, which on light microscopy mimicked the morphologic appearance of MM. Similarly, LRs were identified on MM cells by intense positive staining. Immunoreactivity was also evident on nonneoplastic mesothelioma and adenocarcinoma cells but with greater heterogeneity and less intensity. It may be concluded from these results that (a) malignant mesotheliomas have the ability to synthesize components of the basement membrane; (b) enhanced attachment to extracellular matrix by MM would be anticipated as laminin receptors are present in large numbers on the surface of mesothelioma cells; (c) the reason for lack of intensiveness by MM cells remains speculative; type IV-specific collagenase may play a role in regulating this function in these tumor cells.