Use of antivenom for snakebites reported to United States poison centers

No Change in the Use of Antivenom in Copperhead Snakebites in Ohio

INTRODUCTION

Historically, copperhead snake (Agkistrodon contortrix) envenomations were not treated with antivenom owing to related adverse events and little benefit. However, recent studies have shown improved outcomes with antivenom use. We hypothesized that the frequency of antivenom use for copperhead envenomation in Ohio has increased as benefits of administration became more widely known.

METHODS

All copperhead snakebites reported to the Ohio poison control centers from 2006 through 2016 were compiled. Antivenom use, bite severity, and disposition were abstracted. A nonparametric test for trend was used to evaluate changes over time for the number of patients treated with antivenom and patient disposition. Logistic regression was used to assess the odds of admission vs discharge with antivenom administration, bite severity, age, and sex as independent variables.

RESULTS

Ninety-eight patients reported copperhead snakebites to the poison control centers. The test of trend showed no change in the proportion of patients treated with antivenom by year (P=0.42). There was no difference in the proportion of patients discharged home (P=0.38) per year. Logistic regression showed antivenom use was associated with an odds ratio for admission of 46.7 (95% CI: 7.3-296.4).

CONCLUSIONS

The frequency of antivenom use for copperhead bites did not significantly increase between 2006 and 2016. Administration of antivenom was associated with a large increase in the odds of admission to the hospital, even when controlling for bite severity. Further education regarding the benefits and safety of antivenom may increase its use for copperhead snakebites, but may lead to an increase in hospital admissions.

Fatal Snakebite Envenoming and Agricultural Work in Brazil: A Case-Control Study

We investigated the association between fatal snakebite envenoming and agricultural work in Brazil, considering the effects of relevant covariables. A nested case-control study was performed using 1,119 fatal cases of snakebite envenoming among persons aged ≥ 10 years, notified to the Brazilian official reporting system, from 2004 to 2015. As controls, 4,476 cases were randomly selected from the 115,723 nonfatal cases of snakebite, without missing data, that occurred in the same time period. The main predictor was occupation in the agriculture sector; the main outcome was death by snakebite envenoming. Logistic regression analysis was used to investigate the main association, controlling for the effects of relevant covariables. Fatal cases had a 20% greater chance (odds ratio [OR] = 1.20; 95% confidence interval [CI]: 1.00-1.39) of being among farmers than the controls. However, late (≥ 6 hours) time to treatment (OR = 2.00; 95% CI: 1.70-2.36); adequate antivenom with an insufficient (OR = 1.25; 95% CI: 1.04-1.50) or excessive (OR = 4.89; 95% CI: 4.10-6.03) number of vials; inadequate antivenom and insufficient or excessive number of vials (OR = 3.87; 95% CI: 2.40-6.24); no use of antivenom (OR = 2.05; 95% CI: 1.60-2.64); and age ≥ 60 years (OR = 1.98; 95% CI: 1.61-2.44) were more strongly associated with lethality. Lethality was 1.0% in the period, being 0.47% among those receiving early and adequate treatment. We concluded that in Brazil, fatal snakebite envenoming was associated with agricultural work, controlling for relevant covariates. However, quality of health care provided and greater age were much more strongly associated with lethality.

Cottonmouth snake bites reported to the ToxIC North American snakebite registry 2013-2017

Introduction: The majority of venomous snake exposures in the United States are due to snakes from the subfamily Crotalinae (pit vipers). There are three types of US pit vipers: rattlesnakes (Crotalus and Sisturus spp.) copperheads (Agkistrodon contortrix), and cottonmouths (Agkistrodon piscivorus) also known as water moccasins. Cottonmouth bites are reported less frequently than other pit viper envenomations, and data on cottonmouth envenomation are limited. Our objective was to describe the epidemiology, clinical manifestations, and management of cottonmouth envenomations using prospective data reported to the Toxicology Investigators Consortium's (ToxIC) North American Snakebite Registry (NASBR)Methods: Cottonmouth envenomation cases reported to NASBR for the period from January 1, 2013, through December 31, 2017 were reviewed. Variables collected included patient demographics, bite location, clinical manifestations, and management.Results: Thirty-one cottonmouth envenomations were reported. Most bites occurred in children aged 7-12 (39%). Most bites involved the lower extremity (72%). Intentional interaction with the snake occurred in three cases (10%). Swelling was the most reported clinical effect and occurred in all patients. Gastrointestinal symptoms were reported in 19% of patients, and 19% developed coagulopathy. Antivenom treatment was used in 84% of patients. Nineteen patients (61%) required hospital stays of >24 hours.Discussion: Our study represents the first systematic prospective data collection on cottonmouth bites. Our data demonstrate that cottonmouth envenomations cause primarily local effects and, occasionally, systemic toxicity. Our study also demonstrates that antivenom is often indicated for these envenomations per published guidelines and recommendations.Conclusions: Cottonmouth envenomations are relatively infrequent. However, they can cause significant local and systemic toxicity. Most cottonmouth envenomations in this series were treated with antivenom and were hospitalized beyond 24 hours.

Snakebites and climate change in California, 1997-2017

BACKGROUND

Climate change effect on flora and fauna has been scientifically documented, but the effect on North American venomous snakebites is unknown. The objectives were to examine Californian snakebite incidence and correlate with weather patterns and climate changes.

METHODS

A retrospective analysis of snakebites reported to the Californian Poison Control System from 1 September 1997 to 30 September 2017. Venomous snakebite reports were aggregated by caller zip code, and correlated per county with weather data, air temperature, precipitation, population data, eco-regions, and land characteristics. Time series decomposition by seasonality and trend, regression, and autocorrelation were used to assess association between climate variables and incidence.

RESULTS

There were 5365 reported venomous snakebites during the study period, with a median age of 37 years (22-51) with 76% male (p < .001, 95% CI 75.6-77.9%). Most snakebite outcomes were coded as minor (1363, 25%) or moderate (2607, 49%), with three deaths. Adjusted for population, the annualized incidence of snakebites statewide slightly decreased (rho = -0.11, p = .65). The snakebite incidence per million people rose after a period of no drought and declined during drought (r = -0.41, p ≪ .01). Snakebite incidence decreased by 6-month prior drought (-3.8% for each 10% increase in drought), and increased by 18-month prior precipitation (+3.9% for each 10% increase in precipitation).

CONCLUSIONS

Patterns of precipitation and drought had a significant and predictive effect on snakebites in California over a 20-year period. Snakebite incidence decreased following drought, and increased after precipitation.

Misidentification of copperhead and cottonmouth snakes following snakebites

INTRODUCTION

Copperhead (Agkistrodon contortrix) and cottonmouth or water moccasin (Agkistrodon piscivorus) snakes account for the majority of venomous snakebites in the southern United States. Cottonmouth snakes are generally considered to have more potent venom. Copperheads are considered less venomous and there is some controversy as to whether or not bites from copperhead snakes need to be treated with antivenom. Copperhead and juvenile cottonmouth snakes are both brown in color. The purpose of this study was to evaluate the accuracy of identification by the public and healthcare providers between these two species.

METHODS

Snakebite victims sometimes bring dead snakes to the hospital or have taken pictures of the snake. When this occurred, ED personnel were asked to take a picture of the snake, and forward the picture to the state poison control center. The identification of the snake by witnesses and/or hospital personnel was compared to the identification by the state herpetologist.

RESULTS

During the study period, there were 286 cases of snakebites reported to the state poison control center. Pictures were obtained on 49 of the responsible snakes. All copperhead snakes were identified correctly by callers. However, only 21% of cottonmouth snakes were identified correctly, with 74% of cottonmouth snakes being identified as copperheads. Both public and medical personnel performed poorly on identification of cottonmouth snakes.

CONCLUSIONS

Forty percent of the snakes identified as copperheads were actually cottonmouth snakes. Juvenile cottonmouth snakes were often identified as copperhead snakes.

Time to treatment and severity of snake envenoming in Brazil

Objective

To analyze the relationship between time to treatment and severity of snakebite envenomation in Brazil.

Methods

This case-series retrospective study analyzed 144 251 snakebite cases in Brazil between 2007 and 2015, as reported to the Brazilian Notifiable Diseases Information System. The main dependent variable was snakebite envenomation severity (mild/moderate/severe). The main predictor was time to treatment (early (< 6 hours) vs. delayed (≥ 6 hours)). Covariables were snake type (Bothrops/Crotalus/Micrurus/Lachesis), patient's age and sex, bite site, and treatment at a specialized care center (center/noncenter). Polytomous logistic regression techniques were used to control the covariates and assess confounding and effect modification.

Results

The time to treatment variable was strongly associated with the severity of snakebite envenomation. Snake type and treatment at specialized care center modified the main association effect. The association between delayed time to treatment and envenomation severity was consistently stronger among patients treated at specialized care centers than among those who were not treated at such centers. Odds ratios tended to increase significantly from moderate to severe envenomation for cases within the subgroups “Center + Bothrops” (1.37 to 2.05), “No center + Bothrops” (1.25 to 1.47), “Center + Crotalus” (1.35 to 3.03), “No center + Crotalus” (0.97 to 2.72), and “Center + Lachesis” (1.22 to 1.89).

Discussion

This study confirmed the classical hypothesis that the time between snakebite and initiation of medical care is associated with severity of snakebite envenomation. It is therefore necessary to provide snakebite victims early access to specialized medical care, particularly to antivenom therapy.

Snakebites Treated in North Carolina Emergency Departments, October 2013-September 2015

INTRODUCTION

North Carolina (NC) is home to more than 30 species of indigenous venomous and nonvenomous snakes. Snakebites can cause debilitating and potentially fatal injuries. However, there is a lack of current information available describing the incidence of snakebites in NC. Therefore, we performed this study of snakebites treated in NC emergency departments (EDs) using the statewide syndromic surveillance system, the North Carolina Disease Event Tracking and Epidemiologic Collection Tool (NC DETECT).

METHODS

This was a descriptive epidemiologic study characterizing NC ED visits collected by NC DETECT between October 1, 2013 and September 30, 2015 with an assigned International Classification of Diseases, 9th Revision, Clinical Modification code or keyword indicating a snakebite.

RESULTS

Over the 2-year period, the absolute count of snakebite-related ED visits was 2080 visits with an incidence rate of 10.4 visits per 100 000 person-years (95% confidence interval: 10.0-10.9). The frequency of snakebite was highest during the summer months and evening hours. Men had higher incidence rates of snakebite-related ED visits than women, and residents of the Coastal Plain geographic region of NC had higher incidence rates than persons in other regions.

CONCLUSIONS

The current study indicated that snakebites are common injuries treated at NC EDs, with a strong seasonal and geographic component. Additional research is needed to further characterize the circumstances associated with snakebites for the development of preventive measures and public health education.

Incidence and mortality due to snakebite in the Americas

BACKGROUND

Better knowledge of the epidemiological characteristics of snakebites could help to take measures to improve their management. The incidence and mortality of snakebites in the Americas are most often estimated from medical and scientific literature, which generally lack precision and representativeness.

METHODOLOGY/PRINCIPAL FINDINGS

Authors used the notifications of snakebites treated in health centers collected by the Ministries of Health of the American countries to estimate their incidence and mortality. Data were obtained from official reports available on-line at government sites, including those of the Ministry of Health in each country and was sustained by recent literature obtained from PubMed. The average annual incidence is about 57,500 snake bites (6.2 per 100,000 population) and mortality is close to 370 deaths (0.04 per 100,000 population), that is, between one third and half of the previous estimates. The incidence of snakebites is influenced by the abundance of snakes, which is related to (i) climate and altitude, (ii) specific preferences of the snake for environments suitable for their development, and (iii) human population density. Recent literature allowed to notice that the severity of the bites depends mainly on (i) the snake responsible for the bite (species and size) and (ii) accessibility of health care, including availability of antivenoms.

CONCLUSIONS/SIGNIFICANCES

The main limitation of this study could be the reliability and accuracy of the notifications by national health services. However, the data seemed consistent considering the similarity of the incidences on each side of national boundaries while the sources are distinct. However, snakebite incidence could be underestimated due to the use of traditional medicine by the patients who escaped the reporting of cases. However, gathered data corresponded to the actual use of the health facilities, and therefore to the actual demand for antivenoms, which should make it possible to improve their management.

Does the traditional snakebite severity score correctly classify envenomated patients?

OBJECTIVE

This study aims to help set domestic guidelines for administration of antivenom to envenomated patients after snakebites.

METHODS

This retrospective observational case series comprised 128 patients with snake envenomation. The patients were divided into two groups according to the need for additional antivenom after the initial treatment based on the traditional snakebite severity grading scale. One group successfully recovered after the initial treatment and did not need any additional antivenom (n=85) and the other needed an additional administration of antivenom (n=43).

RESULTS

The group requiring additional administration of antivenom showed a higher local effect score and a traditional snakebite severity grade at presentation, a shorter prothrombin and activated partial prothrombin time, a higher frequency of rhabdomyolysis and disseminated intravascular coagulopathy, and longer hospitalization than the group that did not need additional antivenom. The most common cause for additional administration was the progression of local symptoms. The independent factor that was associated with the need for additional antivenom was the local effect pain score (odds ratio, 2.477; 95% confidence interval, 1.309 to 4.689). The optimal cut-off value of the local effect pain score was 1.5 with 62.8% sensitivity and 71.8% specificity.

CONCLUSION

When treating patients who are envenomated by a snake, and when using the traditional snakebite severity scale, the local effect pain score should be taken into account. If the score is more than 2, additional antivenom should be considered and the patient should be frequently assessed.

Iron and carbon monoxide prevent degradation of plasmatic coagulation by thrombin-like activity in rattlesnake venom

Thousands suffer poisonous snake bite, often from defibrinogenating species annually. Three rattlesnake species in particular, the timber rattlesnake, Eastern diamondback rattlesnake, and Southern Pacific rattlesnake, cause clinically relevant hypofibrinogenemia via thrombin-like activity in their venom. It has been demonstrated that iron (Fe) and carbon monoxide (CO) change the ultrastructure of plasma thrombi and improve coagulation kinetics. Thus, the present investigation sought to determine if pretreatment of plasma with Fe and CO could attenuate venom-mediated catalysis of fibrinogen via thrombin-like activity. Human plasma was pretreated with ferric chloride (0-10 μM) and CO-releasing molecule-2 (0-100 μM) prior to exposure to 2.5-10 μg/ml of venom obtained from the aforementioned three species of rattlesnake. Coagulation kinetics were determined with thrombelastography. All three snake venoms degraded plasmatic coagulation kinetics to a significant extent, especially diminishing the speed of clot growth and strength. Pretreatment of plasma with Fe and CO completely abrogated the effects of all three venoms on coagulation kinetics. Further in vitro investigation of other pit viper venoms that possess thrombin-like activity is indicated to see if there is significant conservation of venom enzymatic target recognition of specific amino acid sequences such that Fe and CO can reliably attenuate venom-mediated catalysis of fibrinogen. These data also serve as a rationale for future preclinical investigation.

Prospective study of recovery from copperhead snake envenomation: an observational study

BACKGROUND

Although much is known about signs, symptoms, and management in the acute phase of crotaline snake envenomation, little is known about signs, symptoms, function, and quality of life during the recovery phase. The purpose of this observational pilot investigation is to evaluate the utility of several clinical outcome instruments in the setting of copperhead snakebite, and to characterize the clinical course of recovery.

METHODS

This is a multi-center prospective, open-label, observational study of patients envenomated by copperhead snakes. We administered the Disabilities of the Arm, Shoulder, and Hand (DASH), Lower Extremity Functional Scale (LEFS), Patient-Specific Functional Scale (PSFS), Work Productivity and Ability Impairment: Special Health Problem (WPAI: SHP), Patients' Global Impression of Change (PGIC), Patient's Global Assessment of Recovery (PGAR), and SF-36 instruments, obtained numeric pain rating scales, and measured grip strength, walking speed, and swelling prior to hospital discharge and 3, 7, 14, 21, and 28 days after envenomation.

RESULTS

20 subjects were enrolled; none were lost to follow-up. Most (80%) had moderate severity swelling, and most (75%) received antivenom. Across the broad range of measures, abnormalities of pain, swelling, impairments of physical and role function, and quality of life persisted for 7-14 days in most subjects. Validated self-reported outcome measures, such as the DASH, LEFS, PSFS, PGIC, SF-36, and the daily activities impairment portion of the WPAI: SHP were more responsive than measurements of swelling or walking speed. Data quality issues limited the utility of the work impairment portion of the WPAI: SHP. Residual signs, symptoms, and impairment in some subjects lasted through the 28-day study period. The study design precluded any assessment of the effectiveness of antivenom.

CONCLUSIONS

Signs, symptoms, impaired function, and decreased quality of life typically last 7 - 14 days after copperhead envenomation. Several tools appear responsive and useful in studying recovery from pit viper envenomation.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01651299.

Severe adverse drug reaction following Crotalidae Polyvalent Immune Fab (Ovine) administration for copperhead snakebite

OBJECTIVE

To present the case of a severe anaphylactic/anaphylactoid reaction to Crotalidae Polyvalent Immune Fab (Ovine) in a patient bitten by a copperhead snake.

CASE SUMMARY

A 68-year-old man presented with progressive envenomation after receiving a copperhead snakebite on each hand. Crotalinae Fab antivenom was administered. While the initial and only dose was partially infusing, the patient developed an adverse drug reaction (ADR) of urticaria and hypotension, which resolved with cessation of the infusion, recurred with resumption of the infusion, and ultimately was completed with supportive care. An additional episode of hypotension, urticaria, and angioedema occurred shortly after antivenom therapy completion. Epinephrine was administered, resolving the reaction with complete patient recovery. The event received a Naranjo score of 10, indicating a definite ADR.

DISCUSSION

Treating copperhead snakebites with antivenom is a matter of debate. Concern over adverse events and cost induce some physicians to manage copperhead bites without antivenom because they are generally milder in severity.

CONCLUSION

As demonstrated in this case, severe ADR can occur with Crotalinae Fab antivenom, and its efficacy for copperhead envenoming needs to be better established via placebo-controlled, randomized trials.

Ethical considerations in design of a study to evaluate a US Food and Drug Administration–approved indication: Antivenom versus placebo for copperhead envenomation

Background:

In 2000, the US Food and Drug Administration approved CroFab® Crotalidae Polyvalent Immune Fab, ovine (FabAV), which had received orphan drug designation, for use in patients with minimal to moderate North American crotaline envenomations including copperhead snakes. As existing evidence on the effectiveness of FabAV for this indication is limited, wide practice variation in its use exists. In order to provide more definitive clinical evidence as to the role of this treatment, a new randomized, placebo-controlled trial of FabAV specifically for copperhead bites was initiated.

Purpose:

In light of the existing US Food and Drug Administration approval, ethical considerations of participation in this trial have been raised. We discuss the ethical principles pertinent to this randomized, placebo-controlled trial with placebo arm. We apply an accepted framework for ethical research to this trial. Due to the evidence gap in the literature, wide-ranging treatment recommendations by medical experts, and broad practice variation, clinical equipoise exists in the treatment of copperhead envenomation with FabAV. The impact of this clinical equipoise on the value and scientific validity of the trial is discussed. The trial’s risk–benefit ratio is also considered. Potential risks to the patients are minimized as the protocol includes a plan for rescue therapy in the event that patients progress to severe envenomation symptoms. Overall, risks are further minimized by the inclusion of an interim analysis with stopping rules based on demonstrated efficacy should the therapy clearly prove to be beneficial.

Conclusion:

Although a post-marketing clinical study of this nature is unusual for an approved indication, this trial adheres to all ethical preconditions found in existing guidelines for clinical research involving human subjects.

Treating venomous snakebites in the United States: a guide for nurse practitioners

This article discusses the current, evidence-based guidelines for managing venomous snakebites indigenous to the United States. A review of common varieties of venomous snakes, venom effects, risk factors for snakebites, and management strategies are presented to assist nurse practitioners in caring for snakebite victims.

Challenges of managing snakebite envenomation in a deployed setting

Snake bite envenomation causes a significant health burden globally, especially in austere or resource poor settings. This case series describes envenomation in two adults and two children presenting to the Role 3 Medical Treatment Facility in Camp Bastion, Afghanistan. Each case has similarities with respect to the coagulopathy of envenomation but differs in terms of time delay to presentation and response to treatment, including reactions to antivenom. We discuss the challenges and ethical dilemmas in delayed-presentation snakebite, the diagnosis and treatment of coagulopathy and the role of antivenom and surgical debridement.

North American snake and scorpion envenomations

Envenomations by snakes and scorpions in North America, although uncommon, do occur, and the victims may seek medical treatment. Combined, snake and scorpion encounters result in more than 25,000 calls a year to poison centers. Although some similarities exist with respect to general signs of envenomation and treatment, specific nuances distinguish the medical care to be anticipated and therapies available. Regardless of geographic practice area, exposures will occur that may result in a significant envenomation. This article provides critical care nurses with fundamental knowledge of varied snake and scorpion envenomation presentations and treatments to assist in optimizing patient outcomes.

The use and tolerability of Crotalidae Polyvalent Immune FAB (Ovine) in pediatric envenomations

There are limited data on the use of Crotalidae Polyvalent Immune FAB-Ovine (CroFab) in the management of crotalid envenomations in children. Thus, the primary objective of this retrospective chart review was to evaluate the safety and tolerability of CroFab in a pediatric population. Over an 8-year time period at this institution, there were 204 admissions for snakebite of which 82 received CroFab. Children who received CroFab were more often associated with bites to the hands and fingers and tended to have more significant envenomations as indicated by longer hospital stays, greater tissue injury, and a tendency to require surgery more often. Six (7.3%) of the 82 patients who received CroFab experienced an adverse drug reaction. Reactions consisted of allergic symptoms that were mild, responded to minimal interventions, and did not limit the subsequent use of CroFab. It is concluded that CroFab use is typically well tolerated in pediatric patients.

Incidence of immediate hypersensitivity reaction and serum sickness following administration of Crotalidae polyvalent immune Fab antivenom: a meta-analysis

OBJECTIVES

  Crotalidae polyvalent immune Fab (ovine) (FabAV) is commonly used in the treatment of symptomatic North American crotaline snake envenomation. When approved by the U.S. Food and Drug Administration in 2000, the incidences of immediate hypersensitivity reactions and serum sickness were reported as 0.14 and 0.18, respectively. The objective of this meta-analysis was to evaluate the incidence of immediate hypersensitivity reactions and serum sickness reported in studies of patients treated with FabAV therapy after North American crotaline envenomation.

METHODS

  The authors searched PubMed, Ovid MEDLINE, and EMBASE from January 1, 1997, to September 20, 2010, for English-language medical literature and cross-referenced bibliographies of reviewed articles. The published abstracts of the major toxicology conferences were also searched. All prospective and retrospective cohort studies with patients receiving FabAV therapy for North American crotaline envenomations were eligible for data abstraction. Two content experts reviewed full-text articles and extracted relevant study design and outcome data. Proportions of immediate hypersensitivity and serum sickness for each study were analyzed in a random-effects model to produce an overall estimate of immediate hypersensitivity and serum sickness incidence associated with FabAV administration.

RESULTS

  The literature search revealed 11 unique studies of patients who received FabAV that contained information on immediate hypersensitivity reactions and serum sickness. The meta-analysis produced a combined estimate of the incidence of immediate hypersensitivity of 0.08 (95% confidence interval [CI] = 0.05 to 0.11) and a combined estimate of the incidence of serum sickness of 0.13 (95% CI = 0.07 to 0.21).

CONCLUSIONS

  In this systematic literature review and meta-analysis, the combined estimates of the incidence of immediate hypersensitivity reactions and serum sickness from FabAV in the treatment of symptomatic North American crotaline envenomations appear to be lower than previously reported, at 0.08 and 0.13, respectively.

Unified treatment algorithm for the management of crotaline snakebite in the United States: results of an evidence-informed consensus workshop

BACKGROUND

Envenomation by crotaline snakes (rattlesnake, cottonmouth, copperhead) is a complex, potentially lethal condition affecting thousands of people in the United States each year. Treatment of crotaline envenomation is not standardized, and significant variation in practice exists.

METHODS

A geographically diverse panel of experts was convened for the purpose of deriving an evidence-informed unified treatment algorithm. Research staff analyzed the extant medical literature and performed targeted analyses of existing databases to inform specific clinical decisions. A trained external facilitator used modified Delphi and structured consensus methodology to achieve consensus on the final treatment algorithm.

RESULTS

A unified treatment algorithm was produced and endorsed by all nine expert panel members. This algorithm provides guidance about clinical and laboratory observations, indications for and dosing of antivenom, adjunctive therapies, post-stabilization care, and management of complications from envenomation and therapy.

CONCLUSIONS

Clinical manifestations and ideal treatment of crotaline snakebite differ greatly, and can result in severe complications. Using a modified Delphi method, we provide evidence-informed treatment guidelines in an attempt to reduce variation in care and possibly improve clinical outcomes.