TRENDS in ULTRASOUND USE in LMI Countries

 

Results

Initial database search (after deduplication) yielded 6,276 articles (Figure 1). Abstracts were reviewed for inclusion, after which 1,713 studies were excluded for not reporting ultrasound use, describing non-clinical applications, or for studies not performed in an LMIC. An additional 287 articles were included in the novel research sub-category as defined above. Nine articles that met novel research criteria were excluded after the full-text was not available for review, with an additional 5 articles excluded for being research studies conducted in a military setting.

Trends by year and geographical region of ultrasound use in LMICs for all studies and novel ultrasound studies are shown in Figures 2 and 3. 

The number of countries with reported ultrasound use has increased 24% since 2010 from 50 to 62 countries. The countries with the highest number of ultrasound studies included India (20%), Egypt (9.8%), Nigeria (8.8%), and Pakistan (7.3%). The specialties represented in all ultrasound studies included cardiology (25%), obstetrics and gynecology (14%). 

Other key specialties included gastroenterology (7.3%), pediatrics (5.8%), infectious disease (5.7%), internal medicine (6.2%), endocrinology (2.9%), and general surgery (3.5%). The most common journals of publication were the Indian Heart Journal (n=103), the Pan African Medical Journal (n=77), the Journal of Medical Case Reports (n=57), Mymensingh Medical Journal (n=53), Pakistan Journal of Medical Sciences (n=50), PLoS ONE (n=48), and BMC Research (n=44).

Of the 287 novel ultrasound application studies, 48% were prospective studies, 13% qualitative, 12% retrospective, 11% cross-sectional studies, 8% case reports, 5% randomized controlled trials, and 1.0% case-controls. Studies were largely performed at public hospitals (86%), of which 59% were conducted at tertiary hospitals and 41% were carried out in a primary care or rural setting. Novel research studies in the form of RCTs are shown in Table 1.

The novel applications of ultrasound technology in novel studies was primarily for screening (26%) and obstetrical use (34%), however, key applications also included infectious disease (10%), cardiology (9%), abdominal conditions (8%), trauma (8%), and gynecologic conditions (3%). Ultrasound imaging providers in novel studies included physicians (85%), midwives (7%), residents (3%), community health workers (2%), and ultrasound technicians (2%). Hand-held ultrasound devices were used in 28% (n=47) of novel studies. 

The most common journals of publication for novel ultrasound research include the Journal of Ultrasound in Medicine (n=12), BMC Pregnancy and Childbirth (n=7), Critical Ultrasound Research (n=7), PLoS ONE (n=6), Egyptian Journal of Radiology and Nuclear Medicine (n=5), the Egyptian Journal of Chest Diseases and Tuberculosis (n=5), and the American Journal of Tropical Medicine and Hygiene (n=5).

Global collaboration, defined as the inclusion of at least one author whose listed publication affiliation was within the country in which the novel ultrasound study was conducted, was present in 70% of studies. The majority of studies that involved global collaboration occurred in India (n=22), Uganda (n=22), Nigeria (n=15) and Tanzania (n=15). Of first authors, 67% were from the country of ultrasound study, of last authors, 60% were from the country of ultrasound study. A total of 75 papers (26%) included both a first and last author from the country of ultrasound study, including 18 from India and 14 from Nigeria. Thirty one percent of novel ultrasound research was funded (n=91), including by NIH grants, the Bill and Melinda Gates Foundation, the General Electric (GE) Foundation, and European foundation grant funding. The countries with the most number of studies with funding were Uganda (n=13), Tanzania (n=10), and Rwanda (n=6). Using the Cochrane risk of bias tool, 70% of the studies reviewed were characterized of having more than one categorized medium and high risk of bias for at least one ‘Risk of Bias’ category.

Sixty eight percent of novel research studies (n=196) contained an educational or training component on ultrasound imaging. Of those educational studies, 91 (46.4%) occurred in the subSaharan geographical region, including a majority in Uganda (n=20), Nigeria (17), and Tanzania (n=9). 

Details of educational studies with funding and known ultrasound, including a description of the training program or curriculum, are shown in Table 2. 

The number of annual educational ultrasound studies has increased to nearly 2.9 times the amount from 2010 to 2018 (from 14 to 40 per year).

Discussion

Increasing Use of Ultrasound

Our systematic literature review of ultrasound use in LMICs demonstrates the growing utilization of this relatively low-cost, portable imaging technology in low resource settings. Although the WHO does not measure access to ultrasound alongside other imaging modalities such as CT and MRI, it does recognize the importance of ultrasound imaging and its potential impact on diagnostics worldwide.

This includes a goal of meeting 90% of imaging needs in primary health care settings with the use of a general purpose ultrasound machine combined with an X-ray unit, along with distribution of the WHO published Manual of Diagnostic Ultrasound. Our study demonstrates that research studies regarding ultrasound use in LMICs have increased nearly 60% and expanded 20% geographically in the last ten years in efforts to meet those goals. However, evidence also suggests that the majority of ultrasound studies were conducted at tertiary care centers (more than 70% of all ultrasound studies) and within middle income countries, demonstrating broader problems with lack of access to healthcare in low-income economies and especially in rural areas.

Regional Trends of Ultrasound

Examining the regional breakdown of ultrasound related studies in LMICs, our study determined that nearly 70% of studies involved ultrasound usage originating from Southeast Asia and sub-Saharan Africa. In terms of novel ultrasound research conducted in LMICs, the region with the most studies was Western and sub-Saharan Africa (46.7%), driven by research conducted in Nigeria, Uganda, and Tanzania. 72% of studies involved global collaboration, meaning an author from an LMIC was present in the final publication. This lack of representation of authors from LMICs indicates that global collaboration could and should be increased, with the goal of 100% of research efforts and the subsequent academic publications involving collaboration with LMIC partners in the country where the research was conducted. This represents a potential lack of representation seen in other areas of publication.

Focus of Studies

The majority of ultrasound studies focused on cardiology, which described usage of portable echocardiograms, and obstetrics where the use of ultrasound in prenatal care is standardized. Pediatric care, gastroenterology, and internal medicine were specialties that conducted substantial research with ultrasound in the LMICs. Looking at novel applications of ultrasound, we found the increasing application of US as a screening tool was utilized, with novel applications including screening for Crimean-Congo hemorrhagic fever in Turkey, human cystic echinococcosis in Morocco, and dengue fever severity in India. 

 Other noteworthy applications of novel ultrasound research included the deployment of a wind-up powered fetal heart monitor in Uganda conducted by Byaruhanga et al and the development of a machine learning model to classify chronic liver disease severity based on liver ultrasound in India by Bharti et al.

Types of Studies

Many studies on the use of ultrasound in LMICs were qualitative studies understanding the perceptions of ultrasound use, most commonly examining community perceptions of routine ultrasound imaging during pregnancy. Of note, perceptions about routine prenatal ultrasound care among physicians, midwives, and patients were studied. For example, the use of ultrasound in standard prenatal care was measured in several countries, as it represented a new phenomenon and was found to be essential to improving maternal outcomes. Key studies conducted in Tanzania, Uganda, Nigeria, Ghana evaluated the changing perception of obstetric ultrasound use for prenatal care. We found that ‘novel ultrasound research’ was published more often in international journals than ‘applications of ultrasound’ studies, which were commonly published in regional journals, i.e. PLoS ONE versus the Indian Heart Journal.

Educational Programs

We found that the rate of educational studies remained relatively consistent over the period studied. However, many of the educational studies focused on task-shifting from skilled providers to training for lay providers including midwives, medical students, community health workers, or other lay people. This includes the emerging role of teleconsultation services and tele-imaging in ultrasound around the world. For example, Bansal et al conducted the VISION-in-Tele-Echo study which evaluated the benefit of a teleremote training program in echocardiography in India, and Colquhoun et al conducted a pilot study of nurse￾led rheumatic heart disease echocardiography screening in Fiji. Furthermore, some studies combined educational training programs alongside a measurable impact on increased screening and diagnosis. The study conducted by Chamadol et al outlined the teleconsultation program launched in Thailand for the diagnosis of cholangiocarcinoma, while simultaneously capturing the additional patients screened and health centers impacted by the program. Finally, the availability of ultrasound gel was identified as a potential barrier to use due to cost and lack of availability of commercially produced ultrasound gel. Several studies outlined low cost recipes for generic ultrasound gel, including the use of shampoo, Guar Gum, corn starch, lotion, and Betadine.

Overall Trends

Our study identified the overall trend of increasing studies in ultrasound application in LMICs over the past decade. There has been increased use of ultrasound with new applications of technology simultaneously focused on the increased application in rural health care centers. Furthermore, research in ultrasound studies indicates a trend of increased training programs, using teleremote technologies to expand task shifting to lay providers, and ingenuity in using this low-cost technology in new ways adapted for low-resource settings. 

The findings outlined in the literature indicated the increased scope of ultrasound and its use in LMICs, where such a low cost, portable, diagnostic imaging modality is an extremely valuable tool. 

Furthermore, the study has identified the potential for hand-held technology to make this imaging modality widely available at a potentially low cost. 

Care providers should keep in mind barriers to use, including patient and provider perceptions, level of skill, power availability, and the lack of technical repair when designing ultrasound related programs on a global basis.

Conclusion and Global Health Implications

In conclusion, this literature review focused on ultrasound trends and usage in LMICs. With the decreasing cost of ultrasound equipment and increasing availability of handheld ultrasound devices, it is important to continue assessment of the adoption and effective novel application of ultrasound technology in LMICs. Furthermore, there is a pressing need to address the potential capabilities and delineate limitations of ultrasound within resource limited settings. We found evidence of the role of educational training programs increasing screening and diagnostic clinical decision making. We also found the increasing adoption of  ultrasound technology globally.