Good Authority Of A Clinical Guideline Essay Example

Type of paper: Essay

Topic: Score, Study, Criteria, Physical Education, Medicine, Nursing, Risk, Aliens

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Words: 2475

Published: 2021/01/07

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Pulmonary embolism (PE) is a condition that requires prompt diagnosis and treatment. In the ED, a current guideline pertains to the investigation of possible PE. It employs the Wells criteria as a clinical decision rule in predicting the likelihood or not of PE. Alternative criteria has since been developed such as the Geneva score and the PERC. It needs to be known if the Wells score remains the best tool for use in predicting PE diagnosis. A PICO question was formulated leading to the search, retrieval, and appraisal of related studies. The use of standard criteria is recommended in the ED in conjunction with D-dimer testing among low-risk patients. However, the choice of criteria depends on the prevalence of PE in the patient case mix and is needed in fully answering the clinical question. A higher prevalence requires the use of high-specificity tools such as the Wells score. A low prevalence warrants the use of high-sensitivity tools such as the Geneva criteria.


Pulmonary embolism is a life-threatening complication of thromboembolic diseases such as deep vein thrombosis (DVT). It occurs because of the degradation of a clot and subsequent travel of the embolus where it lodges in the blood vessels of the lung. A guideline in the workplace pertains to the investigation of pulmonary thromboembolic disease in the Emergency Department. The guideline requires the use of the “Pulmonary Embolus Risk Assessment” tool or Wells criteria to determine the patient’s risk of pulmonary embolism (PE). The level of risk determines what investigations should be conducted, i.e. D-dimer blood test, lung ventilation/perfusion (V/Q) scan, CT pulmonary angiography (CTPA), or pulmonary angiography (PA). The purpose of this paper is to locate and appraise evidence supporting the Wells criteria in the detection of PE.


A clinical question assists in structuring the search for related evidence. Using the PICO framework, the population is adult patients, and the intervention is utilisation of the PEs Risk Assessment tool. The intervention will be compared with other methods of assessment, and the outcomes are the occurrence of PE or confirmed diagnoses of PE. Thus, the clinical question is “Is the PE Risk Assessment tool more effective than other clinical decision rules and methods in predicting PE occurrence or diagnosis in adult patients admitted to the ED?”


A search of the Medline, CINAHL, ScienceDirect and Cochrane databases was done using the following search terms: pulmonary, embolus, risk, assessment, Wells, score, and criteria. There were 3 search strings used: “pulmonary embolus risk assessment” (Search String 1), “Wells score” (Search String 2), and “Wells criteria” (Search String 2). The search in each database was set to rank the articles according to relevance. Studies with titles indicating probable relevance to the PICO question were chosen and screened using the abstracts. Where the results exceeded 50, only the first 50 articles were screened for availability in full text and the English language.
The articles were then assessed for eligibility. Inclusion criteria include publication within the last 10 years and primary research such as randomised controlled trial, quasi-experimental study, or cohort study and systematic reviews or meta-analyses. Other inclusion criteria are a study sample consisting of adults in the Emergency Department (ED), comparison with another tool, and diagnosis-related outcomes. The exclusion criteria are use of a paediatric or obstetric study sample, secondary research, lack of comparison, and a focus on outcomes other than diagnosis.
The use of Search String 1 in Medline resulted in 1,131 articles with 5 studies potentially useful. Search String 2 led to 147 results with 9 studies selected while Search String 3 had 24 results with 3 articles chosen. A search of the CINAHL database using Search String 1 had 262 results with 7 potentially useful articles. Search String 2 had 26 results with 4 useful articles, and Search String 3 had 5 results with no useful articles. In the ScienceDirect database, Search String 1 had 99 results and 5 studies were found potentially useful. Search String 2 yielded 458 results with 17 potentially relevant studies, and Search String 2 had 238 results with 11 articles selected. There were no results for both Search String 1 and Search String 3 in the Cochrane Library. Search String 2 had 8 results with no relevant articles.
Of the total 69 articles selected based on their titles, 13 were duplicates and reduced the number to 56. Screening of the abstracts led to the exclusion of 17 articles because they were either not available in full text or were in a foreign language. The remaining 39 studies were subjected to inclusion and exclusion criteria leading to 7 quantitative studies. The 32 studies were excluded because they were review articles, focused on other outcomes, had no comparison, or were conducted in paediatric and obstetric settings.


Of the 7 articles that fulfilled the inclusion criteria, 5 were chosen for appraisal because of their recency and representativeness of comparison tools. One of the studies compared the Wells score with its modified version, and 3 of the scores compared the Wells criteria with clinical gestalt, the Geneva score, and the Pulmonary Embolism Rule-out Criteria (PERC). The fifth study was a meta-analysis of studies on clinical decision tools and clinical gestalt. It was included because it represents the highest quality of evidence available on the topic.
In a single-centre retrospective study, Engelberger et al. (2011) compared the diagnostic performance of the original and modified Wells score in inpatients and outpatients suspected of having DVT. The original Wells score consisted of 9 items pertaining to conditions, treatments, or signs and symptoms that are risk factors to thromboembolism. If present in the patient, 8 of these items constitute a score of 1 with the score per item summed up into a total score. The 9th question pertains to the physician’s judgment as to whether an alternative diagnosis is less likely than PE. If so, 2 points are deducted from the total score. A score of ≤ 0 is considered low risk; a score between 1 and 2 corresponds to intermediate risk; and a score of ≥ 3 is considered high risk. The modified Wells score includes a 10th item which is a prior history of DVT.
A sample of 477 adult patients, 69% of whom were outpatients, were prospectively assessed for risk factors to thromboembolism and scored using the original Wells criteria (Engelberger et al., 2011). The same patients were then re-assessed retrospectively using the modified Wells criteria. The outcome was the incidence of PE within 3 months post discharge. The statistical analysis was intended to compare the discriminatory power of the two criteria in predicting embolism. The results showed that the absolute risk classification that the two criteria had no significant differences in predictive ability.
Meanwhile, Penaloza, Melot and Motte (2011) compared the Wells tool to the modified Geneva score in terms of the probability of accurately predicting PE in a single-centre retrospective study of ED patients. The authors’ premise in conducting the study was that the Wells tool was not standardised completely, and there is the inclusion of an item that relies on the subjective judgment of physicians. The authors found that the simplified Geneva score addresses these two limitations. The risk for PE was evaluated in a sample of 339 adult patients using the original Wells criteria and retrospectively assessed using the Geneva tool. The scores were correlated with actual diagnoses of PE using D-dimer tests, and other diagnostic procedures.
The Geneva score relies completely on objective measures including patient age, prior history of DVT or PE, history of surgery or fracture, active cancer, lower extremity pain, pain following deep palpation of the extremity, unilateral oedema, haemoptysis, and heart rate (Penaloza, Melot & Motte, 2011). Each item is also scored and classified into low, moderate or high risk. The analysis showed a significant statistical difference between the two criteria with the Wells tool demonstrating a higher accuracy in predicting PE in high-risk patients.
Another retrospective study compared the Wells criteria to both the revised Geneva score and unstructured clinician gestalt in terms of the pre-test probability of accurately predicting PE (Penaloza et al., 2013). Gestalt refers to the physician’s unstructured clinical assessment of the likelihood of PE, categorised as low, intermediate or high, without the use of clinical decision rules such as the Wells score. The study employed a large sample of 1,038 patients across 116 EDs located in France and one in Belgium. The study settings best represented the reality in most EDs where physicians have varying levels of experience.
The ED physicians documented their gestalt assessments of patients prior to using the Wells or Geneva scores. Three months after ED discharge, the patients were followed up for PE events or deaths. The results showed that using gestalt led to a significantly higher number of low-risk and high risk scores compared to both the Wells and Geneva criteria (Penaloza et al., 2013). Gestalt also resulted in a lower prevalence of PE among patients with low or intermediate risk and a higher prevalence in high-risk patients. A major limitation of the study was its use of a previous study’s prospective data. The authors concluded that gestalt demonstrates a better predictive capability for PE.
Aydogdu et al. (2014) employed the prospective study design in a single centre to examine the differences in the capacity to prevent the over-investigation of PE in the ED between Wells criteria and the Pulmonary Embolism Rule-out Criteria (PERC). Over-diagnosis pertains to the unnecessary use of costly diagnostic procedures such as the D-dimer test and CT angiography. The major difference between the PERC and Wells scores is that the former is intended to rule out PE while the latter stratifies patients according to risk. The PERC consists of 8 questions that, in the event of “no” answers to all, signifies that PE can be safely ruled out and no further tests are necessary.
A major limitation of the study was the small sample consisting of 125 patients who underwent the diagnostic procedures upon the recommendation of an ED physician or pulmonologist. The sample was grouped into those who turned out positive for PE and those with a subsequent negative diagnosis. The Wells and PERC scores were computed retrospectively and compared with the results of diagnostic procedures. The Wells criteria showed 43% sensitivity, 78% specificity, a positive predictive value of 66%, and a negative predictive value of 59% (Aydogdu et al., 2014). Meanwhile, the PERC tool demonstrated 98% sensitivity, 7% specificity, 50% positive predictive value, 80% negative predictive value, 93% false positivity rate, and 2% false negativity rate (Aydogdu et al., 2014). The Wells score was also found to correlate well with D-dimer levels.
Given these values, the authors concluded that the use of PERC and the Wells score in conjunction with D-dimer can safely rule out PE (Aydogdu et al., 2014). Because of the differences in values, the authors recommend that the PERC be used in patient populations with a PE prevalence that is lower than 10% and in low-risk patients. This is because of its high sensitivity or the ability to rule out the condition. Conversely, the Wells score is more appropriate in populations with a PE prevalence of more than 10% and in those patients at high risk for the condition owing to the tool’s high specificity or its ability to rule in the condition (Aydogdu et al., 2014).
Given the alternative tools to the Wells criteria, the meta-analysis conducted by Lucassen et al. (2011), elucidates further the differences among them. The authors systematically searched two databases to locate studies that investigated clinician gestalt and clinical decision rules in determining the diagnostic probability of PE. A total of 52 studies fulfilled the inclusion criteria with an aggregate sample of 55,268 patients. The settings included the ED and inpatient units. Fifteen studies focused on gestalt, 30 studies were on the original and modified Wells criteria, 5 studies pertained to the original Geneva criteria, and 4 studies on the modified Geneva criteria. The quality of the studies was determined and showed acceptable quality (Lucassen et al., 2011). The authors’ conclusion was that the sensitivity of the gestalt and clinical decision rules by themselves was inadequate in safely excluding PE especially in low-risk patients (Lucassen et al., 2011). When combined with the D-dimer test, the sensitivity becomes sufficient.


Except for the meta-analysis, the quality of the retrospective studies is ranked as Level IV evidence based on the Melnyk and Fineout-Overholt evidence hierarchy (Muehlbauer et al., 2009). Taken individually, the retrospective studies demonstrate that using the original and modified Wells score does not make a significant difference in predictive ability (Engelberger et al., 2011). Compared with gestalt, the performance of the Wells score is inferior (Penaloza et al., 2013) but is superior compared to the modified Geneva score (Penaloza, Melot & Motte, 2011). The Wells criteria cannot be compared with PERC as the patient case mix defines the appropriateness of each tool (Aydogdu et al., 2014). Given the level of evidence of the studies and each study’s focus on only one comparison tool, it is difficult to generate practice recommendations. The meta-analysis categorised as Level I evidence pools together the data from 52 studies that investigated all the above tools and provides stronger evidence that can be used to frame clinical guidelines (Lucassen et al., 2011). Its use of a pooled sample of 55,268 patients and related statistical analysis lends authority to the authors’ recommendations.
The appraisal of the studies shows that the use of a clinical decision rule using a standard tool, as demonstrated by the selected clinical practice guideline, is appropriate (Lucassen et al., 2011). However, a major consideration that needs to be ascertained is the prevalence of PE in the ED patient population. A high prevalence justifies the choice of using the Wells score (Aydogdu et al., 2014; Lucassen et al., 2011). If the choice is supported by the patient case mix, the performance of a D-dimer test when the Wells score is low, as indicated in the guideline, improves sensitivity based on the recommendation of Aydogdu et al. (2014) and Lucassen et al. (2011). The rationale is the tool’s low sensitivity. The guideline’s recommendation of subsequent discharge following a negative D-dimer test is supported by evidence as well (Lucassen et al., 2011). The guideline’s support of the use of more invasive methods such as CT angiography in patients with intermediate or high Wells scores is also best practice given the tool’s high specificity (Aydogdu et al., 2014; Engelberger et al., 2011; Penaloza, Melot & Motte, 2011).


Pulmonary embolism is an adverse event that requires immediate treatment to prevent death. However, it can be difficult to diagnose and requires invasive and costly procedures to rule in. Therefore, the use of clinical decision rules is necessary to accurately rule out negative cases and rule in positive cases leading to timely treatment and the prevention of over-diagnosis. In addition to the PE Risk Assessment tool or Wells score, there are other criteria developed for this purpose. A search and appraisal of the literature is necessary to ascertain if the current practice guideline in the ED is evidence-based. What is known is that there is strong evidence supporting the use of standard clinical decision rules such as the Wells score in the investigation of PE in the ED. Until the prevalence of PE in the ED case mix is known, however, the PICO questions cannot be answered definitively.


Aydogdu, M., Sinanoglu, N.T., Dogan, N.O., Oguzulgen, I.K., Demircan, A., Bildik, F., & Ekim, N.N. (2014). Wells score and Pulmonary Embolism Rule Out Criteria in preventing over investigation of pulmonary embolism in emergency departments. Tuberk Toraks, 62(1), 12-21. doi: 10.5578/tt.6493.
Engelberger, R.P., Aujesky, D., Calanca, L., Staeger, P., Hugli, O., & Mazzolai, L. (2011). Comparison of the diagnostic performance of the original and modified Wells score in inpatients and outpatients with suspected deep vein thrombosis. Thrombosis Research, 127, 535-539. doi:10.1016/j.thromres.2011.02.008.
Lucassen, W., Geersing, G., Erkens, P.M.G., Reitsma, J.B., Moons, K.G.M., Buller, H., & van Weert, H.C. (2011). Clinical decision rules for excluding pulmonary embolism: A meta-analysis. Annals of Internal Medicine, 155, 448-460. doi: 10.7326/0003-4819- 155-7-201110040-00007.
Muehlbauer, P.M., Thorpe, D., Davis, A., Drabot, R., Rawlings, B.L., & Kiker, E. (2009). Evidence-based interventions to prevent, manage, and treat chemotherapy- and radiotherapy-induced diarrhea. Clinical Journal of Oncology Nursing, 13(3), 336- 341. Retrieved from
Penaloza, A., Melot, C., & Motte, S. (2011). Comparison of the Wells score with the simplified revised Geneva score for assessing pretest probability of pulmonary embolism. Thrombosis Research, 127, 81-84. doi:10.1016/j.thromres.2010.10.026.
Penaloza, A., Verschuren, F., Meyer, G., Quentin-Georget, S., Soulie, C., Thys, F., & Roy, P. (2013). Comparison of the unstructured clinician gestalt, the Wells score, and the revised Geneva score to estimate pretest probability for suspected pulmonary embolism. Annals of Emergency Medicine, 62, 117-124. doi:
Appendix 1
Pulmonary Embolus Risk Assessment or Wells Criteria
Engelberger, R.P., Aujesky, D., Calanca, L., Staeger, P., Hugli, O., & Mazzolai, L. (2011). Comparison of the diagnostic performance of the original and modified Wells score in inpatients and outpatients with suspected deep vein thrombosis. Thrombosis Research, 127, 535-539. doi:10.1016/j.thromres.2011.02.008.

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