Speed_Bump_Sign as a Diagnostic Tool for Acute Appendicitis: Comparison
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Please note this is a comparison between Version 2 by Lindsay Dong and Version 1 by Yen Ta Huang.

The ‘speed bump sign’ is a clinical symptom characterised by aggravated abdominal pain while driving over speed bumps. The speed bump sign is a useful ‘rule-out’ test for diagnosing acute appendicitis. With good accessibility, the speed bump sign may be added as a routine part of taking the history of patients with abdominal pain.

  • speed bump sign
  • diagnosis
  • acute appendicitis

1. Introduction

Acute appendicitis (AA) is one of the most common causes of acute abdominal pain that requires emergent surgical intervention [1]. However, clinical diagnosis is always challenging, especially in early disease stages. Presenting symptoms such as fever, anorexia, nausea, vomiting and lower abdominal tenderness are usually difficult to distinguish from gastrointestinal or gynaecological diseases. Laboratory tests are usually non-specific parameters for AA diagnosis. Consequently, delayed diagnosis and surgical intervention increases the risk of appendiceal perforation, which can lead to peritonitis or even death. However, negative appendectomy, which is defined as appendectomy revealing a normal appendix upon histological evaluation, may occur in 5–42% of cases [2]. This finding can be associated with considerable morbidity.
The clinical application of different scoring systems, which include symptoms, signs and laboratory examination, have been investigated to enhance the diagnostic value for AA diagnosis [3]. In the latest guideline of the World Society of Emergency Surgery, the experts strongly recommend the use of scoring systems to exclude AA and identify intermediate-risk patients for the need of imaging surveys based on high certainty of evidence [4]. However, some evidence demonstrated that the scoring system was not as reliable as computed tomography (CT) scans [5]. Accordingly, the experts conditionally suggested against the use of Alvarado score for positive confirmation of AA in adults [4]. The routine use of CT scans is not advocated due to high cost, delay in operative intervention and the risk of radiation exposure [6]. In addition, CT scan is not an ideal tool for complicated appendicitis due to low pooled sensitivity published in a meta-analysis [7]. Magnetic Resonance Imaging (MRI) also demonstrated high accuracy in both high pooled sensitivity and specificity, but it costs much more and takes more time for examination [8]. Although the rate of negative appendectomy in the United States has been consistently declining based on the abovementioned strategies, the rate of negative appendectomy remains up to 8.47% [9]. Looking for harmless, costless and accessible indicators to improve the diagnostic test accuracy of AA is still warranted.
Speed bumps, which are frequently used as traffic devices to slow down the speed of vehicles, can be used as a clinical symptom with aggravated abdominal pain while driving over speed bumps (i.e., ‘speed bump sign’) [2]. One of the reasons for pain with AA is due to inflammation of the peritoneum, and it is possible that the impact of going over a bump irritates the parietal layer of peritoneum by stretching or moving as with rebound tenderness [10]. This sign is used by some doctors while obtaining patient history from abdominal pain cases. Pain aggravation while travelling over speed bumps is thought to be associated with an increased likelihood of AA. However, the certainty of its evidence has not been validated. Using systematic review to search and collect all the similar research studies, appraise the risk of bias and further perform meta-analysis if suitable is the standard strategy in the field of evidence-based medicine. The methodological strength of meta-analysis is more efficient to present a combined result by pooling the sample size to increase statistical power than to report the results of each individual study. As such, this study aimed to perform a meta-analysis and analyse the applicability of the speed bump sign through a comprehensive methodology of evidence-based medicine in the diagnosis of appendicitis in patients with acute abdominal pain.

2. ‘Speed Bump Sign’ in Acute Appendicitis Diagnostics

The speed bump sign provided an easy indicator in predicting AA upon the arrival of a patient with abdominal pain at an emergency room. The diagnostic odds ratio (DOR) ratio is a single indicator of how informative a diagnostic test is that is independent of the prevalence of the disease/disorder [21][11]. Higher DOR may be indicative of better test performance. In the past studies, pooled DORs of various indicators for AA diagnosis have been reported, such as Alvarado score (7.99) [22][12], Raja Isteri Pengiran Anak Saleha Appendicitis (RIPASA) score (24.66) [22][12], neutrophil-to-lymphocyte ratio (14.34) [23][13], procalcitonin (21.4) [24][14], abdominal ultrasound (6.88) [25][15], CT (129.6) [8] and MRI (129.6) [8]. CT and MRI are without doubts the most accuracy tool for AA diagnosis. 

If a test displays a high sensitivity, it will detect the disease or disorder with confidence; if the results of the test are negative, there is certainty that no disease or disorder is present. Therefore, a high sensitivity test helps to rule out the disease/disorder when the result is negative, which is called the mnemonics of SnNout [26][16]. On the other hand, the mnemonics of SpPin indicates that a high specificity test helps rule-in a disease/disorder with a high degree of confidence if the result is positive. Based on the pooled estimates in our study, the high sensitivity of increasing pain while driving over speed bumps is a basis for yielding a strong rule-out value to exclude AA. Since 1980, many score systems have been developed for the diagnosis of appendicitis, and the most widely used system is Alvarado score. This system, including eight parameters with clinical symptoms and laboratory data (migration of pain, anorexia, nausea, tenderness over right lower quadrant, rebounding pain, elevated body temperature, leukocytosis and shift of white blood cell count to the left) is considered a reasonable and simple system that can be used easily in clinics or emergency departments [27][17]. However, the pooled sensitivity of the Alvarado score for the diagnosis of appendicitis is only 69% (95% CI = 67–71%) in a recent meta-analysis [22][12]. Another system is Raja Isteri Pengiran Anak Saleha Appendicitis (RIPASA) score, which consists of two demographic information (gender and age), five symptoms (right iliac fossa pain, migration of right lower quadrant pain, anorexia, nausea and vomiting and duration of symptoms), five signs (right iliac fossa tenderness, right iliac fossa guarding, rebound tenderness, Rovsing’s sign and elevated body temperature) and two laboratory data (raised white blood cell count and negative urine analysis); it has been considered the most accurate scoring system for AA diagnosis [28][18]. The pooled sensitivity of the speed bump sign is similar to RIPASA score (94%, 95% CI = 92–95%) [22][12], indicating the value of the speed bump sign in clinical applications. In addition, unnecessary CT scans can be avoided because of the similar pooled sensitivity between speed bump sign and CT (95%, 95% CI = 93–96%) [29][19]; consequently, medical cost and radiation exposure can be reduced.

The low specificity (49%) of the speed bump sign indicates that patients do not definitely have AA, although they experience aggravating pain when they pass speed bumps during travel. In fact, the specificity of RIPASA score is also low (55%, 95% CI = 51–59%) [28][18]. Further examination with high specificity in a case with a positive speed bump sign should be performed. 

Speed pump sign can be a good tool for AA screening in the triage of emergency medical services. However, applying likelihood ratios [LR (+) and LR (−)] for clinical judgement may be more useful in daily practice [31][20]. LR represents how much more likely a diagnostic tool is amongst people who have specific clinical presentation than amongst people who do not have the presentation [31][20]. The pretest probability of an individual case may rely on a physician’s subjective experience and objective information, such as physical examinations, laboratory tests and image findings. Weighted judgement, or posttest probability in statistics, can be changed following the consideration of LR. Indeed, the results demonstrated that the negative finding of the speed bump sign in a patient with abdominal pain can be applied as a strong hint to exclude the diagnosis of AA. However, probabilities of 28% are still not good enough when the pretest probability is as high as 75% with negative speed sign. Combining with the Raja IPASA steri Pengiran Anak Saleha Appendicitis (RIPASA) score and speed bump sign may provide higher sensitivity for AA diagnosis. Procalcitonin, an indicator for systemic bacterial infection, provided better pooled specificity than sensitivity for AA diagnosis [24][14]. Therefore, a new scoring system including both speed bump sign and procalcitonin might be more helpful. Such evidence should be confirmed by future research.

The low specificity (49%) of the speed bump sign indicates that patients do not definitely have AA, although they experience aggravating pain when they pass speed bumps during travel.

3. Conclusions

The speed bump sign provided very high sensitivity and very low LR (−), which could be considered as a useful tool to exclude AA if not mentioned by patients. However, further examinations are still needed for making surgical decisions on patients with a positive presentation of the speed bump sign. Uneven road surfaces or potholes on the ground may provide similar effects to those of a speed bump, with the former more often being encountered. Considering it a common phenomenon when a patient heads to a hospital, questioning about the ‘speed bump sign’ should be added to the routine questionnaire when doctors take history from patients with abdominal pain.

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