a b s t r a c t

Introduction: The primary concern of emergency physicians (EPs) in symptomatic patients in their early preg- nancy is to rule out Ectopic pregnancy by identifying a definite Intrauterine pregnancy (IUP). Then an assessment of viability is required for the IUPs. Although Transvaginal ultrasound (TVUS) stands as the best modality for these patients, it is not available in most emergency settings. This study aimed to investigate the effects of high- frequency linear transducers (HFLT) on the accuracy of Point-of-care ultrasound for detection of IUP and the agreement between EPs and obstetricians for patients’ diagnosis.

Method: A convenience sample of pregnant patients who presented to the emergency department (ED) with vag- inal bleeding and Abdominopelvic pain was included. The characteristics of diagnostic tests of transabdominal POCUS performed by EPs were compared to TVUS. Results: The study population was finalized as 143 patients. For the definite IUP, the diagnostic accuracy of POCUS was 93.0%, with a sensitivity of 89.0%, a specificity of 100%, compared to an accuracy of 97.9% for POCUS plus HFLT with a sensitivity of 96.7%, a specificity of 100%. For the identification of fetal Cardiac activity (FCA), utilizing HFLT improved the diagnostic accuracy to 97.9% (from 94.4%) and sensitivity to 95.5% (from 88.1%). In addition, the agreement between the EPs and obstetricians concerning the classification of ED diagnosis was excellent (agree- ment: 96.5%, kappa: 0.943, p < 0.0001).

Conclusion: POCUS plus HFLT performed by EPs in evaluating symptomatic patients in their first-trimester preg- nancy improves the accuracy to a non-inferior level compared to TVUS performed by obstetricians. Hence, EPs can securely rely on POCUS to confirm IUP and FCA. However, they should be cautious about using it as a rule- out tool. Moreover, HFLT use could enhance the accuracy of POCUS in viability assessment as an alternative to TVUS.

(C) 2022

1. Introduction

Emergency physicians (EPs) frequently encounter patients with Vaginal bleeding and abdominopelvic pain in their early pregnancy. The primary concern of the EP facing these patients is to rule out ectopic pregnancy by identifying a definite intrauterine pregnancy . The rate of ectopic pregnancy in symptomatic patients who presented to the emergency department (ED) is reported as high as 16%, with a mor- tality rate of 9% [1]. Hence, EP should consider any patients presenting with a positive pregnancy test, abdominal pain, and vaginal bleeding to have an ectopic pregnancy until proven otherwise. The second most important concern in the ED with these patients is to evaluate possible

Abbreviations: HFLT, High-frequency linear transducers; IUP, Intrauterine pregnancy; EM, Emergency medicine; POCUS, Point-of-care ultrasound.

* Corresponding author.

E-mail address: [email protected] (A. Celik).

complications of early pregnancy. One of these common complications is miscarriage, and approximately one-third of women of reproductive ages experience an early pregnancy loss before 20 weeks [2].

The American Institute of Ultrasound in Medicine (AIUM) and American College of Radiology (ACR) positioned ultrasound (US) as the first-line imaging modality for the evaluation of symptomatic pa- tients in the First-trimester pregnancy [3]. Sonographic identification of the intrauterine Gestational sac (GS) containing a yolk sac (YS) or fetal part (FP) with or without fetal cardiac activity (FCA) is essential to declare a definite IUP. Furthermore, a detailed assessment of these structures should be performed to comprehend the viability of the preg- nancy. In this regard, transvaginal ultrasound (TVUS) has been investi- gated extensively for the diagnosis of non-Viable IUP [2,4]. TVUS performed by EPs was supported by the literature regarding diagnostic accuracy and the effects on length of stay in ED [5-9]. However, endocavitary transducers are unique tools that are not feasible for other sonographic procedures with a high cost and a necessity for

https://doi.org/10.1016/j.ajem.2022.08.045

0735-6757/(C) 2022

dedicated areas. Additionally, using TVUS in ED may cause significant anxiety or embarrassment and endocavitary transducers also require a high-level disinfection after use which can be challenging for EDs. Hence these transducers are not available in most EDs.

High-frequency linear transducers (HFLT) are used extensively for various purposes such as fetal echocardiography, superficial tissue US, vascular US, and musculoskeletal US [10-12]. We hypothesized that its combination with curved abdominal transducers might provide diag- nostic benefits.

In this prospective observational study, we sought to investigate whether the integration of HFLT into the Point-of-care ultrasound was associated with better diagnostic accuracy for definite IUP, and complications of early pregnancy, in patients presenting to the ED with abdominal pain and or vaginal bleeding when compared to traditional transabdominal approach. Secondly, we aimed to study the effects of HFLT on the agreement between EP and Obstetric consul- tants regarding the diagnostic classifications of patients.

1. Materials and methods
   1. Study design

This was a prospective, observational diagnostic accuracy study per- formed at the adult ED of an academic tertiary care hospital between March 2019 and April 2021. The approximate annual volume of patients was about 135.000 visits per year for the study period. The study proto- col adhered to the STARD 2015 guidelines, and the study was approved by the institutional review board (ID: 40465587-75, and approval num- ber: 2018/75).

• 1. Selection of participants and data collection

All women (18 and above) in their first trimester of pregnancy (with a positive pregnancy test, serum Beta-human chorionic gonadotropin: ?-hCG) who presented to the ED with vaginal bleeding and or abdominopelvic pain were eligible for enrolment. Any patients who presented to ED during the shifts of the sonographers were included in the study. We excluded the patients who refused to provide consent, who refused the transvaginal ultrasound against the medical advice, who were referred from another hospital with a known diagnosis, who previously received an ultrasound for the current complaints, who were referred to the consultant before POCUS, and who discharged without obstetrics and gynecology consultation.

The patient management was made according to the clinical policies and guidelines for patients presenting to ED in early pregnancy [13]. The patient’s demographic data, obstetric history, vitals, gestational age of fetus according to last menopausal period, ?-hCG value, signs, and symptoms were recorded during the initial evaluation.

• 1. Methods of measurement
     1. Index test; emergency ultrasound and EP diagnosis

All sonographic examinations were performed by three sonogra- phers certified for advanced bedside ultrasound by the national emer- gency medicine society: an attending physician (seven years of experience in POCUS with an average of 750 ultrasounds per year, and two senior residents (three years of experience with about 200 ultra- sounds per year). The residents received two hours of didactic course and practiced in first-trimester ultrasound for three weeks before pa- tients’ enrollments. Then the residents performed >20 POCUS examina- tions individually and recorded two transverse and sagittal planes images. After approval of the recorded images by the experienced so- nographer (AC), the recruitments were started. Sonographic examina- tions were performed with 3-5 MHz curved transabdominal transducers (CT) and 7-12 MHz High-frequency linear transducers

(HFLT) of two available ultrasound systems (Mindray DC T6; Shenzhen, China, and The Fujifilm FC1; Bothell, WA).

Ultrasound (US) protocol was started with identifying the definite IUP according to the previous literature [3,4,13]. First, patients were ex- amined with an abdominocurved probe in transverse and sagittal planes. In cases of inconclusive results for the presence of definite IUP or FCA, an HFLT was incorporated into the examination with the same scanning technique. The intrauterine presence and characteristics of GS, YS, FP, FCA, and subchorionic hemorrhage (SCH) were evaluated to conclude a definite IUP and to understand the pregnancy’s viability. We used the criteria previously defined to conclude viability [3,14]. If a crown-rump length of >=7 mm without an FCA, and a mean GS diameter of >=25 mm without an embryo existed; a non-viable IUP would be as- sumed. After the sonographic evaluation of uterus and adnexa were fin- ished, the examination for free fluid was conducted in three regions: hepatorenal, splenorenal, and recto-uterine pouches.

Finally, by evaluating the sonographic (POCUS), clinical, and labora- tory findings, the attending EP who takes primary care of the patient classified cases as follows: viable definite IUP, intrauterine fetal demise (IUFD), spontaneous abortion (miscarriage), molar pregnancy, ovarian hyperstimulation syndrome, and ectopic pregnancy with or without rupture. All other cases were considered as unclassified with or without early IUP findings, such as a GS without definite IUP findings and the in- stances with suspicions of ectopic pregnancies without apparent results. Sonographers recorded the standard POCUS findings, interpretations, and EPs’ primary diagnoses electronically. Then, the secondary diagno- sis was recorded after sharing the results of POCUS plus HFLT findings with the attending EP.

• • 1. Transvaginal ultrasound and reference diagnosis

After ED evaluation was finished, all patients were referred to the consultant physicians, the attending obstetrician (or a faculty) responsi- ble for the in-hospital consultations and blinded to the study. These pa- tients underwent an assessment consisting of a history, laboratory findings, pelvic examination, and TVUS. Finally, a blinded abstracter (a junior medical doctor) reviewed the patients’ charts and consultation reports to establish the findings of TVUS and the final diagnosis.

• 1. Sample Size estimation

Historically, Durham et al. reported a sensitivity of 91% for the diag- nosis of IUP via TVUS [15]. We hypothesized that the sensitivity of POCUS plus HFLT should be similar or slightly inferior to TVUS. Hence, to achieve a sensitivity of 90% via a 99% confidence interval (CI) and an expected prevalence of about 40% to 50%, we estimated the required sample size for the study as at 120 to 150, respectively. After calculating the estimated drop-out ratio of 10%, the final sample size was settled as 134 to167.

• 1. Data analysis

Statistical analyses were performed with R-based statistical software (Jamovi software, version 1.6.23; Sydney, Australia; https://jamovi.org). Continuous variables were presented as medians and interquartile ranges (IQR) and categorical variables as number (n) and percentage (%). 2 x 2 contingency tables were formed for Sonographic findings (GS, IUP, FCA, and SCH). Then, the diagnostic accuracy metrics with 95% CI were calculated. Also, Interobserver agreement among patients’ diagnoses between EPs and OCs was studied using the kappa statistics. P-value <0.05 was the accepted statistical significance threshold for all analyses.

1. Results

During the study period, the total number of eligible patients was

185. Of these patients, 36 women (20.6%) refused the transvaginal

Table 1

Demographics and baseline characteristics.

Characteristics, n = 143 Value

Demographics
Age (years), median (IQR)	29 (25, 34)
Gestational age (week from LMP)	7 (6, 9)
B-hcg (mlU/mL)
<1000 mlU/mL, n (%)	19 (13.3)
1000-3500 mlU/mL, n (%)	13 (9.1)
3500-15,000 mlU/mL, n (%)	26 (18.2)
>15,000 mlU/mL, n (%)	85 (59.4)
Obstetric history
Gravidity, n (%)
1	51 (35.7)
2	46 (32.2)
>3	46 (32.2)
Parity, n (%)
0	74 (51.7)
1	37 (25.9)
>1	32 (22.3)
Miscarriage, n (%)
0	87 (60.8)
1	42 (29.4)
>1	14 (9.8)
Symptoms
Pelvic Pain, n (%)	79 (55.2)
Vaginal bleeding, n (%)	107 (74.8)
Nausea and vomiting, n (%)	16 (11.2)
Disposition Admitted, n (%)	31 (21.7)
Discharged, n (%)	104 (72.7)
Discharges against medical advice	8 (5.6)

IQR: Interquartile Range (25p, 75p), LMP: last menopausal period,

ultrasound, and 6 (3.4%) were previously enrolled. As such, the study population was finalized as 143 patients. The median age of pregnant patients was 29 years (IQR; 25, 34), and the median gestational age of fetuses was seven weeks (6, 9). Demographics and baseline characteris- tics of patients and gestations are summarized in Table 1 (See Fig. 1).

Of the study population of 143 women, a definite intrauterine preg- nancy was observed in 91 (63.6%) cases, ectopic pregnancies in 4 (one ruptured), molar pregnancy (MP), and ovarian hyperstimulation syn- drome (OHSS) in 2 cases. POCUS with standard approach identified 81 (56.6%) definite IUP, and 59 (41.2%) revealed fetal cardiac activity. POCUS plus HFLT provided identification of definite IUP in seven more patients and FCA in five more patients (8.7% and 8.5% improvement, re- spectively). With respect to definite IUP, the diagnostic accuracy of POCUS was 93.0% (95% CI: 87.5 to 96.6), with a sensitivity of 89.0%

(95% CI: 80.7 to 94.6), a specificity of 100% (95% CI: 93.2 to 100), com- pared to an accuracy of 97.9% (95% CI: 93.9 to 99.6) for POCUS plus HFLT with a sensitivity of 96.7% (95% CI: 90.7 to 99.3), a specificity of 100% (95% CI: 93.2 to 100). For the identification of FCA, the accuracy

of POCUS was 94.4% (95% CI: 88.4 to 97.1), with a sensitivity of 88.1% (95% CI: 77.8 to 94.7) and a specificity of 100% (95% CI: 95.3 to 100). Uti- lizing HFLT improved the accuracy to 97.9% (95% CI: 93.9 to 99.6) and sensitivity to 95.5% (95% CI: 87.5 to 99.1). The only part of the study where HFLT did not contribute to the diagnostic performance of POCUS was the identification of subchorionic hemorrhage. The diagnos- tic test characteristics of POCUS (with or without HFLT) are summarized in Tables 2-3.

There was an 87.4% crude agreement between the EP and obstetri- cian concerning the classification of ED diagnosis (kappa: 0.803 (95% CI: 0.719 to 0.888), z: 15.278, p < 0.0001). However, HFLT use with POCUS provided a discrimination capability in 14 more unclassified cases, resulting in an excellent agreement level between EPs and obste- tricians (agreement: 96.5%, kappa: 0.943 (95% CI: 0.895 to 0.992), z: 17.894, p < 0.0001). The classification of patients’ diagnoses and the in- terrater agreement characteristics are shown in Table 4.

1. Discussion

In this prospective observational study of a convenience sample of symptomatic patients in their first-trimester pregnancy, we dem- onstrated that the diagnostic accuracy of POCUS integrated with HFLT performed by EPs for identifying IUP was comparable to that of TVUS performed by Obstetricians. Our results showed that POCUS with or without HFLT could be used to safely confirm a defi- nite IUP and FCA without any false-positive cases. Moreover, employing the HFLT in POCUS diminished the false-negative rate (11.0% to 3.3%; and 11.9% to 4.5%, respectively) and -LR (0.11 to 0.03; and 0.12 to 0.04, respectively), indicating the value in even ruling out IUP and FCA.

Previous studies have pointed out that POCUS performed by EPs has reasonable sensitivity and specificity for detecting definite IUPs and ruling out the possibility of ectopic pregnancy that improves ED length of stay [5,8,9,15-17]. A 2010 meta-analysis by Stein et al. showed that the POCUS performed by EPs has a sensitivity of 99.3% and a specificity of 99.9%, indicating that pelvic ultrasound is sufficient to rule out EP by identifying IUP [8]. Although we pri- marily investigated the accuracy of POCUS for the diagnosis of defi- nite IUPs, our findings are consistent with this meta-analysis. All five patients with ectopic pregnancy (one; ruptured ectopic preg- nancy) were suspected or diagnosed by POCUS and referred to con- sultant obstetricians. Moreover, a systematic review by McRae et al. reported that the specificity of POCUS for the diagnosis of IUP ex- ceeds 98% in most studies [9]. They enrolled 878 patients in five studies. However, they did not perform Pooled analysis because of statistical heterogeneity between these studies, different transduc- ers were used, and some do not have clear diagnostic criteria for the IUP. The reported sensitivities of these studies with the objective standards reached 90.6%. The lowest sensitivity (67.2%) was ob- served in the study of Wong et al. that used transabdominal sonog- raphy[18]. This real-world limitation of the transabdominal approach demands Transvaginal sonography for patients with in- conclusive outcomes.

In contrast to the literature, we observed a sensitivity of 89.0%

(95% CI, 80.7-94.6) with the standard POCUS, indicating similarity to the upper limits of these studies. The characteristics of sonogra- phers and the advanced gestational age of fetuses would induce this high sensitivity. As the gestational age of fetuses decreases, the false-negative cases would increase, leading to the difference we ob- served. However, the mean gestational age in our study (7.6 weeks) was not lower than the mean gestational reported by Wong et al. (9 weeks), whereas this data was not shown in the others [18]. Hence, this disparity between our study and others might depend on the experience of sonographers.

To the best of our knowledge, there is only one prospective study addressing the clinical utility of HFLT in first-trimester pregnancy [19]. They reported that the use of HFLT increased the detection rate of IUP dramatically from 81.8% (54/66) to 95.5% (63/66), which is parallel to our results (from 89.0% to 96.7%). We also inves- tigated the Diagnostic test characteristics for IUP and the other sono- graphic findings, such as FCA and SCH. However, they did not perform such an analysis, and endovaginal transducers were only used if needed for the patients with inconclusive results in the previ- ous sonographic examination. EPs performed these sonographic evaluations without a reference diagnostic standard. Hence, our study is unique in this aspect that reveals the diagnostic tests charac- teristics of POCUS with HFLT for these patients. As a result of these findings, we suggest using HFLT, especially in patients without defin- itive findings.

The secondary aim of this study was to investigate the interrater

agreement between EPs (with and without HFLT) and obstetricians in correctly assessing the viability of the pregnancy. When the ED classifi- cations were regarded as a whole, a good agreement (agreement: 87.4%,

Fig. 1. Flow chart of patients.

Abbreviations: IUP: Intrauterine pregnancy, POCUS: Point-of-care ultrasound performed by emergency physicians, TVUS: Transvaginal ultrasound performed by obstetricians, FCA: Fetal cardiac activity, HFLT: High-frequency linear transducer.

kappa: 0.803) was observed with the standard approach and an out- standing agreement level (agreement: 96.5%, kappa: 0.943) with the use of HFLT. Furthermore, no false-positive case was seen for viable IUP or IUFD. The agreement between obstetricians and EPs regarding ED diagnosis is a less studied area. Previously, the agreement between ED diagnosis of EPs and radiologist were investigated, and Panebianco et al. reported a good agreement for ED diagnosis [7]. In that study, the agreement for IUFD was 96.0%, while a fair agreement for the inde- terminate diagnosis (agreement: 76.0%). We observed similar results to this study, revealing more unclassified cases without any false-positive cases in identifying ED diagnosis. However, the utilization of HFLT accu- rately categorized most of the falsely classified cases as expected (18 cases vs. 5 cases). This incorrect classification into the undetermined

Table 2

Sonographic findings of transabdominal POCUS performed by EPs and transvaginal ultra- sound performed by obstetricians.

Standard POCUS POCUS plus HFLT TVUS

	TP	FP	TN	FN		TP	FP	TN	FN		positive	negative
GS	97	1	26	19		113	1	26	3		116	27
IUP	81	0	52	10		88	0	52	3		91	52
FCA	59	0	76	12		64	0	76	3		67	76
SCH	12	1	128	2		12	1	128	2		14	129

TP: true positive, FP: false positive, TN: true negative, FN: false negative, POCUS: Point-of- care ultrasound performed by EPs, IUP: intrauterine pregnancy, FCA: fetal cardiac activity, GS: gestational sac, SCH: subchorionic hemorrhage, TVUS: Transvaginal ultrasound per- formed by obstetricians.

group is a hard bias to avoid because being leery is more critical in ED than being courageous in most circumstances.

• 1. Limitations

First, despite the well-defined criteria for enrollment, it is hard to avoid a selection bias because we enrolled only the patients evaluated during the sonographers’ shifts. In addition, the COVID-19 pandemic causes a significant delay in patients’ enrollment due to the unavailabil- ity of the Ultrasound device. Third, we did not record the data regarding the physical status of the patients, such as weight and body mass index, which could limit the HFLT use. However, the mean distance from the transducer to the GS for the cases HFLT improved accuracy was 3.6 cm (min 3.1; max 4.6), indicating this limitation. Also, only three experi- enced sonographers took part in this study who might be highly trained more than most ED physicians. Moreover, attending physician enrolled more than half of the patients (82 cases), exhibiting the need to be care- ful while generalizing these results. The fifth is a real-world limitation of diagnostic accuracy studies of POCUS that the POCUS examination with- out any abnormality resulted in a substantial number of refusals (19.5% of ours) for obstetric consultation (TVUS). However, this is an ethical condition rather than an actual limitation. Latest, we accepted the cross-sectional data for diagnostic classifications rather than dynamic data from a clinical follow-up, which may have biased our results. How- ever, our primary aim was to perform a diagnostic accuracy assessment for the POCUS plus HFLT compared to TVUS and the agreement between

Table 3 diagnostic utility metrics of the POCUS with the standard transabdominal approach and HFLT for the detection of gestational sac, definite intrauterine pregnancy, fetal cardiac activity, and subchorionic hemorrhage.

	Sensitivity, % (95% CI)	Specificity, % (95% CI)	+ LR (95% CI)	-LR (95% CI)	PPV, % (95% CI)	NPV, % (95% CI)	Accuracy, % (95% CI)
GS by POCUS	83.6	96.3	22.6	0.17	99.0	57.8	86.0
	(75.6-89.8)	(81.0-99.9)	(3.3-154.8)	(0.11-0.26)	(95.6-100)	(42.2-72.3)	(79.2-91.2)
GS by POCUS + HFLT	97.4	96.3	26.3	0.03	99.1	89.7	97.2
	(92.6-99.5)	(81.0-99.9)	(3.8-180.0)	(0.01-0.08)	(95.2-100)	(72.6-97.8)	(93.0-99.2)
IUP by POCUS	89.0 (80.7-94.6)	100 (93.2-100)	?	0.11 (0.06-0.19)	100 (95.6-100)	83.9 (72.3-91.9)	93.0 (87.5-96.6)
IUP by POCUS + HFLT	96.7 (90.7-99.3)	100 (93.2-100)	?	0.03 (0.01-0.10)	100 (95.9-100)	94.5 (84.9-98.9)	97.9 (93.9-99.6)
FCA by POCUS	88.1 (77.8-94.7)	100 (95.3-100)	?	0.12 (0.06-0.23)	100 (93.9-99.9)	90.5 (82.1-95.8)	94.4 (88.4-97.1)
FCA by POCUS + HFLT	95.5	100	?	0.04	100	96.2	97.9
	(87.5-99.1)	(95.3-100)		(0.01-0.13)	(94.4-100)	(89.3-99.2)	(93.9-99.6)
SCH by POCUS	85.7	99.2	100.5	0.14	98.5	92.3	97.9
(+-HFLT) *	(57.5-98.2)	(95.8-99.9)	(15.5-788)	(0.04-0.52)	(94.6-99.8)	(63.9-99.8)	(93.9-99.6)

?: infinity, POCUS: Point-of-care ultrasound performed by EPs, IUP: intrauterine pregnancy, HFLT: High-frequency linear transducer, FCA: fetal cardiac activity, SCH: subchorionic hem- orrhage, GS: gestational sac, PPV: Positive Predictive Value, NPV: Negative Predictive Value, LR: Likelihood ratio, *: the same metrics for POCUS+-HFLT in SCH.

Table 4

Interrater agreement of diagnostic classifications between EPs and Obstetricians.

Diagnosis of Obstetricians with TVUS

	Viable IUP (n = 81)	IUFD (n = 16)	Miscarriage (n = 7)	Unclassified (n = 32)	Ectopic pregnancy (n = 5)	MP- OHSS (n = 2)		Specificity
Viable IUP	77	0	0	0	0	0		100%
IUFD	0	15	0	0	0	0		100%
Diagnosis of Emergency physicians Miscarriage	0	0	7	0	0	0		100%
with POCUS plus HFLT Unclassified	4	1	0	32	0	0		86.5%
Ectopic Pregnancy	0	0	0	0	5	0		100%
MP - OHSS	0	0	0	0	0	2		100%
Sensitivity	95.1%	93.8%	100%	100%	100%	100%		96.5%**
Viable IUP	68	0	0	0	0	0		100%
IUFD	0	11	0	0	0	0		100%
Diagnosis of Emergency physicians Miscarriage	0	0	7	0	0	0		100%
with POCUS Unclassified	13	5	0	32	0	0		64.0%
Ectopic pregnancy	0	0	0	0	5	0		100%
MP- OHSS	0	0	0	0	0	2		100%
Sensitivity	84.0%	68.8%	100%	100%	100%	100%		87.4%*

*: the percent agreement between POCUS and transvaginal ultrasound (TVUS): 87.4%, kappa: 0.803 (95% CI: 0.719-0.888), z: 15.278, p < 0.0001, **: the percent agreement between POCUS plus HFLT (High-frequency linear transducer) and TVUS: 96.5%, kappa: 0.943 (95% CI: 0.895-0.992), z: 17.894, p < 0.0001, Viable IUP: Viable intrauterine pregnancy, IUFD: Intrauterine fetal demise, MP-OHSS: Molar pregnancy-ovarian hyperstimulation syndrome.

EPs and obstetricians. Hence, we do not think that was not an actual lim- itation too.

1. Conclusion

In conclusion, POCUS plus HFLT performed by EPs in evaluating symptomatic patients in their first trimester improves the diagnostic ac- curacy to a non-inferior level compared to transvaginal ultrasound per- formed by obstetricians. Hence, EPs can securely rely on POCUS incorporated with HFLT as an initial modality for confirming IUP and FCA without additional confirmatory testing. However, they should be cautious about using it as a rule-out tool. Moreover, with its excellent degree of agreement, HFLT use could enhance the accuracy of POCUS in viability assessment as an alternative to TVUS.

Funding

None declared.

CRediT authorship contribution statement

Ali Celik: Writing - review & editing, Writing - original draft, Visu- alization, Validation, Supervision, Software, Project administration,

Methodology, Investigation, Formal analysis, Data curation, Conceptual- ization. Mumin Murat Yazici: Writing - review & editing, Writing - original draft, Visualization, Investigation, Data curation. Mehmet Oktay: Investigation, Data curation.

Declaration of Competing Interest

None declared.

Acknowledgments

None declared.

References

1. Alkatout I, Honemeyer U, Strauss A, Tinelli A, Malvasi A, Jonat W, et al. Clinical diag- nosis and treatment of ectopic pregnancy. Obstet Gynecol Surv. 2013;68:571-81.
2. Pontius E, Vieth JT. Complications in early pregnancy. Emergency Med Clin. 2019;37:

219-37.

1. AIUM-ACR-ACOG-SMFM-SRU practice parameter for the performance of standard diagnostic obstetric ultrasound examinations. J Ultrasound Med. 2018:37. https:// doi.org/10.1002/jum.14831.
2. Brown DL, Packard A, Maturen KE, Deshmukh SP, Dudiak KM, Henrichsen TL, et al. ACR Appropriateness Criteria (R) first trimester vaginal bleeding. J Am Coll Radiol. 2018;15. https://doi.org/10.1016/j.jacr.2018.03.018.
3. Beals T, Naraghi L, Grossestreuer A, Schafer J, Balk D, Hoffmann B. Point of care ultra- sound is associated with decreased ED length of stay for symptomatic early preg- nancy. Am J Emerg Med. 2019;37. https://doi.org/10.1016/j.ajem.2019.03.025.
4. Wilson SP, Connolly K, Lahham S, Subeh M, Fischetti C, Chiem A, et al. Point-of-care ultrasound versus radiology department pelvic ultrasound on emergency depart- ment length of stay. World J Emergency Med. 2016;7. https://doi.org/10.5847/ wjem.j.1920-8642.2016.03.003.
5. Panebianco NL, Shofer F, Fields JM, Anderson K, Mangili A, Matsuura AC, et al. The utility of transvaginal ultrasound in the ED evaluation of complications of first tri- mester pregnancy. Am J Emerg Med. 2015;33. https://doi.org/10.1016/j.ajem.2015. 02.023.
6. Stein JC, Wang R, Adler N, Boscardin J, Jacoby VL, Won G, et al. Emergency physician ultrasonography for evaluating patients at risk for ectopic pregnancy: a meta- analysis. Ann Emerg Med. 2010;56. https://doi.org/10.1016/j.annemergmed.2010. 06.563.
7. McRae A, Edmonds M, Murray H. Diagnostic accuracy and clinical utility of emer- gency department targeted ultrasonography in the evaluation of first-trimester pel- vic pain and bleeding: a systematic review. Can J Emergency Med. 2009;11. https:// doi.org/10.1017/S1481803500011416.
8. Barrosse-Antle ME, Patel KH, Kramer JA, Baston CM. Point-of-care ultrasound for bedside diagnosis of lower extremity DVT. Chest. 2021;160:1853-63.
9. Persico N, Moratalla J, Lombardi CM, Zidere V, Allan L, Nicolaides KH. Fetal echocar- diography at 11-13 weeks by transabdominal high-frequency ultrasound. Ultra- sound Obstet Gynecol. 2011;37:296-301.
10. Celik A, Akoglu H, Omercikoglu S, Bugdayci O, Karacabey S, Kabaroglu KA, et al. The diagnostic accuracy of ultrasonography for the diagnosis of rib fractures in patients

presenting to emergency department with blunt chest trauma. J Emerg Med. 2021;60:90-7.

1. Hahn SA, Promes SB, Brown MD. Clinical policy: critical issues in the initial evalua- tion and management of patients presenting to the emergency department in early pregnancy. Ann Emerg Med. 2017;69. https://doi.org/10.1016/j. annemergmed.2016.11.002.
2. Wang PS, Rodgers SK, Horrow MM. Ultrasound of the first trimester. Radiol Clin. 2019;57:617-33.
3. Durham B, Lane B, Burbridge L, Balasubramaniam S. Pelvic ultrasound performed by emergency physicians for the detection of ectopic pregnancy in complicated first- trimester pregnancies. Ann Emerg Med. 1997;29:338-47.
4. Urquhart S, Barnes M, Flannigan M. Comparing time to diagnosis and treatment of patients with ruptured ectopic pregnancy based on type of ultrasound performed: a retrospective inquiry. J Emerg Med. 2022;62:200-6.
5. Recker F, Weber E, Strizek B, Gembruch U, Westerway SC, Dietrich CF. Point-of-care ultrasound in obstetrics and gynecology. Arch Gynecol Obstet. 2021;303:871-6. https://doi.org/10.1007/s00404-021-05972-5.
6. Wong TW, Lau CC, Yeung A, Lo L, Tai CM. Efficacy of transabdominal ultrasound examination in the diagnosis of Early pregnancy complications in an emergency department. Emerg Med J. 1998;15:155-8.
7. Tabbut M, Harper D, Gramer D, Jones R. High-frequency linear transducer improves detection of an intrauterine pregnancy in first-trimester ultrasonography. Am J Emerg Med. 2016;34. https://doi.org/10.1016/j.ajem.2015.11.001.