Extended Abstract
1.    Introduction
Anterior cruciate ligament provides considerable resistance against shearing forces between tibia and femur during activities like walking, running and jumping. Moreover, regarding the induced tension in the ligament, it can help guide arthrokinematics of knee joint. Also, it has an important proprioceptive role due to ample mechanoreceptors. The ACL injury mostly occur between 15 and 25 years old during sport activities with high velocity such as football and basketball (1). Nearly 70% of ACL sport injuries occur during non-contact or minimal contact conditions (1). Following injury, the individual should be assessed instantaneously, but the assessment is limited by pain and edema. The evaluation begins with gait analysis and asymmetries including disappearance of pre-patellar depressions demonstrating edema, hemarthrosis or both could be observed (2). Observation of injury, paraclinical findings and diagnostic tests of injured ligament could be helpful during the evaluation. Diagnostic tests include anterior drawer test, Lachman test, pivot shit test, and lever sign (3-5). The objective of the study was to overview the accuracy and reliability of ACL diagnostic clinical tests.
2.    Methods
Electronic data bases including google scholar, Pubmed, and Science direct were searched to find related articles about the evaluation of ACL injuries between 2013 and 2021. The key words were chosen based on search process including ACL, accuracy and reliability, and clinical tests. The articles were assessed qualitatively by two of the authors of this study using Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2). The checklist is used to evaluate the quality of diagnostic studies and it consists of 4 domains including patient selection, index test, reference standard, flow and timing. Each domain was assessed regarding risk of bias and three first domains were assessed regarding applicability concerns either. The assessors select “yes” for articles with suitable data for each domain and “no” for domains were not clear. Meanwhile, if details were insufficient, “unclear” was recorded. Disagreement between the assessors was resolved with consensus (6).
3.    Results
Following assessment and adaptation processes by inclusion and exclusion criteria, 10 articles were selected and QUADAS-2 score was the same for all the involved articles (Table 1). The results showed that regarding risk of bias in “patient selection” domain, 33% of the articles had low risk, 33% had unclear risk and 33% had high risk. Regarding index test in risk of bias, 80% of the articles were at low risk, 10% had unclear risk and 10% ha high risk. For reference standard domain in risk of bias, 70% had low risk, 20% had unclear risk and 10% had high risk. Flow and timing item in risk of bias domain showed that 20 % of articles were at low risk, 40% were unclear and another 40% were at high risk which was the highest rank of high risk among the evaluated domains. Also, regarding applicability concerns in patient selection domain, 50% of articles were at low risk, 20% had unclear risk, and 30% had high risk. Eventually, for applicability concerns in index test domain, 80% of the articles were at low risk, 10% with unclear risk and 10% with high risk that was completely similar to index test in risk of bias domain. Regarding applicability concerns in reference standard domain, 40% were at low risk, 40% with unclear risk and 20% with high risk.

4.    Conclusion
Several tests are used to diagnose ACL disruption. Anterior drawer, pivot sift, Lachman, and lever sign were used in 9 studies (3,4,7-13). Different values were reported for diagnostic tests. Regarding anterior drawer test, sensitivity and specificity were reported within a range of 21-100% and 80-100% respectively. Also, positive predictive value (PPV) of test was reported between 85 and 94% and negative predictive values of 55-93%. Regarding modified anterior drawer test, specificity equal to 94%, PPV and NPV equal to 90% and sensitivity between 43 and 93% was reported. For lever sign, the articles reported specificity of 50-100%, sensitivity of 33-100%, accuracy of 74-89%, PPV between 47 and 100%, and NPV between 50 and 91%. Considering pivot shift test, specificity of 94-98%, sensitivity of 11-96%, PPV of 91-98%, NPV of 34-81% and accuracy of 71% were reported. For Lachman test, sensitivity was 39-100%, specificity was 63-100%, PPV=81-96%, and NPV=46-91%. Despite the popularity and applicability of the above-mentioned tests, several factors such as clinical experience and knowledge of the assessors, time from disruption, doing test in alertness or under anesthesia, there is no consensus on a particular test.

Ethical Considerations
Compliance with ethical guidelines
There were no ethical considerations to be considered in this research.
Funding
This research did not receive any grant from funding agencies in the public, commercial, or non-profit sectors.
Authors' contributions
All authors equally contributed to preparing article.
Conflicts of interest
The authors declared no conflict of interest.