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Three Part Question

In [a male patient presenting with Acute Scrotum] who undergoes [point-of-care ultrasound (POCUS) to identify testicular torsion] what is the [diagnostic accuracy (sensitivity and specificity)] compared to formal diagnostic ultrasound (DUS) or surgical exploration under anesthesia?

Clinical Scenario

A 14-year-old male presents to the emergency department at 3 A.M. after awakening suddenly from sleep with severe right sided groin pain. A clinical exam of the genitourinary system, with chaperone, is grossly normal, however the cremaster reflex on the right side is equivocal.
You recognize that testicular torsion is an emergent diagnosis on the differential of Acute Scrotum and speak with the Radiologist on Call to arrange a formal ultrasound. The Radiologist asks if you have performed a POCUS?
As you hang-up the phone, you wonder 'what is the diagnostic accuracy of POCUS for testicular torsion?'

Search Strategy

The following databases were searched on April 10th 2021: PUBMED (1996-04/2021) using [MeSH] search terms, MEDLINE (1966-04/2021) using the OVID interface with multi-purpose [.mp] search terms, CINAHL (1982-04/2021) using 'all text' search terms, and both EMBASE (1980-04/2021) and SCOPUS (2004-04/2021) using 'title, abstract and keyword' search terms.
The search strategy was adapted for each database but included the following terms: ("Ultrasound" OR "Ultrasonography") AND ("Testicular torsion" OR "Spermatic Cord Torsion" OR "Acute Scrotum") AND ("Sensitivity and Specificity" OR "Accuracy") LIMIT to BEFORE 2001.
The Cochrane Library was also searched using the strategy: “Testicular Torsion”:ti,ab,kw]

Search Outcome

The search results were as follows:
1. Cochrane Library: 0 Relevant guidelines identified.
2. OVID: 60 search results returned, 16 Studies relevant based on title search, 14 Studies omitted as not addressing population/intervention, 2 original research studies directly relevant to population/intervention.
3. PUBMED: 48 search results returned, 13 Studies relevant based on title, 5 repeated results, 7 studies omitted as not addressing population/intervention, 1 case report identified but full paper unavailable.
4. EMBASE: 43 search results returned, 20 Studies relevant based on title, 5 repeat results, 14 studies omitted as not addressing population/intervention, 1 additional study relevant to research question identified.
5. CINAHL: 27 search results returned, 6 Studies relevant based on title, 4 repeat results, 2 studies omitted as not addressing population/intervention.
6. SCOPUS: 60 search results returned, 14 Studies relevant based on title, 8 repeated results, 6 studies omitted as not addressing population/intervention.

Relevant Paper(s)

Author, date and country	Patient group	Study type (level of evidence)	Outcomes	Key results	Study Weaknesses
A. Nakayama; H. Ide; A. saka; Y. Inoue; Y. Shimomura; T. Iwahata; Y. Kobori; K. Saito; S. Soh; H. Ok 2020 Japan	26 male patients, ages 3-26 years, presenting to the Urology Department with acute scrotum who underwent bed-side color doppler ultrasound (CDUS), performed by a Resident Urologist. All patients subsequently underwent surgical exploration.	Cross-sectional Cohort Study *Inferred, not specified explicitly in manuscript	Number of patients with Testicular Torsion (TT)	13	*NOTE: Results listed as MEAN, (95% Confidence Interval) where available | WEAKNESSES: Limited literature search | Small sample size | Sampling method for patients not stated | Limited demographic data for patient population specified | Exclusion criteria not explicitly stated | Study had multiple aims: (1) to analyze accuracy of ultrasound AND (2) to determine if ultrasound frequency (12Hz vs < 8Hz) impacted diagnosis | Not all accuracy measures were explicitly calculated in the study itself | Results not necessarily generalizable given imaging performed by specialists (urologists) |
			Sensitivity	69.2%, (44.1-94.3)
			Specificity	53.8%, (26.7-80.9)
			Positive Predictive Value	60.0, (35.2-84.8)
			Negative Predictive Value	63.6, (35.2-92.0)
			Positive Likelihood Ratio	1.5, (0.752-2.99)
			Negative Likelihood Ratio	0.571, (0.219-1.490)
			Median time from POCUS to surgical exploration:	3 hours
N. Friedman; Z. Pancer; R. Savic; F. Tseng; M.S. Lee; L. Mclean; D.J. Bagli; M.O. Tessaro 2019 Canada	140 male patients, ages 0-18 years, presenting to a Tertiary Pediatric ED with acute scrotum who underwent POCUS by ED physicians AND formal radiology US or a urological intervention within 24 hours for testicular torsion.	Retrospective Chart Review	Number of patients with Testicular Torsion (TT)	12	*NOTE: Results listed as MEAN, (95% Confidence Interval) where available | WEAKNESSES: Limited literature search | Sampling method for patients not stated | Limited demographic data for patient population specified | Multiple reference standards used (radiological US AND/OR surgical intervention by urology) | The reference standard test was not necessarily interpreted without knowledge of the index test | Results not necessarily generalizable given site’s specialized training in POCUS
			Sensitivity	100%, (73.5-100)
			Specificity	99.1%, (95.0-100)
			Positive Predictive Value	92.3, (63.0-98.8)
			Negative Predictive Value	100
			Positive Likelihood Ratio	108.0 (15.4-759.8)
			Negative Likelihood Ratio	0
			Median time between POCUS and Diagnostic Ultrasound	73 min (Q1 = 51, Q3 =112)
M. Blaivas; P. Sierzenski; M. Lambert 2001 United States of America	36 male patients, ages 10- 62 years, presenting to an Urban Community ED with acute scrotum who underwent POCUS by the ED physician. Diagnosis was verified by either radiology US, scintigraphy or surgical exploration.	Retrospective Chart Review	Number of patients with Testicular Torsion (TT)	3	*NOTE: Results listed as MEAN, (95% Confidence Interval) where available | WEAKNESSES: The 'Accuracy' results presented are in terms of POCUS successfully diagnosing ANY testicular pathology, not only testicular torsion | Sampling method for patients not stated | Limited demographic data for patient population specified | Small sample size | Multiple reference standards used (diagnostic US AND/OR surgery) | Not enough data was provided to reproduce the two-by-two table and calculate the complete set of PPV, NPV, +LR, -LR. | Timeline between POCUS and reference standard not specified | The reference standard test was not necessarily interpreted without knowledge of the index test | Results not necessarily generalizable given sites specialized POCUS resources and training
			Sensitivity	95%, (78-99)
			Specificity	94%, (72-99)
			Positive Predictive Value	Not Calculable
			Negative Predictive Value	Not Calculable
			Positive Likelihood Ratio	15.8
			Negative Likelihood Ratio	0.056
			Median time between POCUS and Gold Standard Test	Not Specified

Comment(s)

Point-of-care ultrasound (POCUS) is an evolving tool that has increasing applications in guiding decision-making in emergency medicine. It has the potential to decrease the morbidity of testicular torsion (TT) by shortening the time from initial triage to urological consultation and treatment by earlier identification of disease. There are limited studies assessing the accuracy of POCUS for TT, and no systematic reviews or randomized control trials were identified. Current literature is limited by small sample sizes, bias inherent to retrospective design, and limited external validity given the specialization and training completed by physicians conducting POCUS in the studies. Nevertheless, the results support the use of POCUS to rule-in TT, with the possibility of forgoing formal DUS and consulting Urology earlier. However, PoCUS should not be relied upon solely to rule OUT the diagnosis, and a negative POCUS should still be followed up with a formal ultrasound or urologic consultation.

Clinical Bottom Line

POCUS can be considered to RULE-IN Testicular Torsion and facilitate earlier consultation to Urology for assessment and ongoing management. However, performing POCUS should not delay definitive care or formal DUS if otherwise available. Further, POCUS should not be used to RULE-OUT testicular torsion. Further research is needed to build stronger evidence.

References

1. A. Nakayama; H. Ide; A. saka; Y. Inoue; Y. Shimomura; T. Iwahata; Y. Kobori; K. Saito; S. Soh; H. Ok The Diagnostic Accuracy of Testicular Torsion by Doctors on Duty Using Sonographic Evaluation with Color Doppler American Journal of Men’s Health 2020; 1-6
2. N. Friedman; Z. Pancer; R. Savic; F. Tseng; M.S. Lee; L. Mclean; D.J. Bagli; M.O. Tessaro Accuracy of point-of-care ultrasound by pediatric emergency physicians for testicular torsion Journal of Pediatric Urology 2019; P608.E1-608.E6
3. M. Blaivas; P. Sierzenski; M. Lambert Emergency evaluation of patients presenting with acute scrotum using bedside ultrasonography Academic Emergency Medicine 2001; 90-39