Point-of-Care Ultrasound by Nonexpert Operators Demonstrates High Sensitivity and Specificity in Detecting Gallstones: Data from the Samoa Typhoid Fever Control Program

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  • 1 Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, Maryland;
  • | 2 Department of Medicine, University of Maryland School of Medicine, Baltimore, Maryland;
  • | 3 Department of Pediatrics, University of Maryland School of Medicine, Baltimore, Maryland;
  • | 4 Samoa Typhoid Fever Control Program, Ministry of Health, Government of Samoa, Apia, Samoa;
  • | 5 Institute for Genome Sciences, University of Maryland School of Medicine, Baltimore, Maryland;
  • | 6 Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, Maryland;
  • | 7 Tupua Tamasese Meaole Hospital, Ministry of Health, Government of Samoa, Apia, Samoa;
  • | 8 Microbiological Diagnostic Unit Public Health Laboratory, Department of Microbiology and Immunology, The University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Melbourne, Australia;
  • | 9 Murdoch Children’s Research Institute, Royal Children’s Hospital, Melbourne, Australia

Approximately 90% of chronic typhoid carriers with persistent Salmonella enterica serovar Typhi (S. Typhi) gallbladder infection have gallstones. In Samoa, where typhoid fever has been endemic for many decades, risk factors predisposing to the development of gallstones are increasing among adults. The Samoa Typhoid Fever Control Program dispatches a “Typhoid Epidemiologic SWAT Team” to perform a household investigation of every blood culture-confirmed case of acute typhoid fever. Investigations include screening household contacts to detect chronic carriers. Following limited training, two nonexpert ultrasound operators performed point-of-care ultrasound (POCUS) on 120 Samoan adults from August to September 2019 to explore the feasibility of POCUS to detect individuals with gallstones during household investigations and community screenings. POCUS scans from 120 Samoan adults in three cohorts (28 food handlers, two typhoid cases and their 18 household contacts, and 72 attendees at an ambulatory clinic) were reviewed by a board-certified radiologist who deemed 96/120 scans (80%) to be interpretable. Compared with the radiologist (gold standard), the nonexpert operators successfully detected 6/7 Samoans with gallstones (85.7% sensitivity) and correctly identified 85/89 without gallstones (95.5% specificity). The proportion (24/120) of uninterpretable scans from this pilot that used minimally trained clinicians (who are neither radiologists nor ultrasound technicians) indicates the need for additional training of POCUS operators. Nevertheless, this pilot feasibility study engenders optimism that in the Samoan setting nonexperts can be trained to use POCUS to diagnose cholelithiasis, thereby helping (along with stool cultures and Vi serology) to identify possible chronic S. Typhi carriers.

Author Notes

Address correspondence to Myron Levine, Center for Vaccine Development and Global Health, 685 W. Baltimore St.—HSF 1 Room 480 Baltimore, MD 21201. E-mail: mlevine@som.umaryland.edu

These authors contributed equally to this work.

Financial support: This work was supported by Bill and Melinda Gates Foundation award number OPP1194582 (INV-000049) (PI: Prof. Myron M. Levine). The World Health Organization supported M. M. L.’s consultation to Samoa in 2013. M. M. L. is supported in part by the Simon and Bessie Grollman Distinguished Professorship at the University of Maryland School of Medicine. M. J. S. received research support in part by federal funds from National Institutes of Health under National Institute of Allergy and Infectious Diseases grants F30AI156973 and U19AI110820 as well as National Institute of Diabetes and Digestive and Kidney Diseases training grant T32DK067872 and by funds from the State of Maryland.

Authors’ addresses: Seth Hoffman, Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, MD, and Department of Medicine, University of Maryland School of Medicine, Baltimore, MD, Current affiliation: Division of Infectious Diseases and Geographic Medicine, Department of Medicine, Stanford University School of Medicine, Stanford, CA, E-mail: sethhoffman@stanford.edu. Sachin Desai, Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, MD, Department of Pediatrics, University of Maryland School of Medicine, Baltimore, MD, and Samoa Typhoid Fever Control Program, Ministry of Health, Government of Samoa, Apia, Samoa, E-mail: sndesai@som.umaryland.edu. Michael Sikorski, Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, MD, Samoa Typhoid Fever Control Program, Ministry of Health, Government of Samoa, Apia, Samoa, Institute for Genome Sciences, University of Maryland School of Medicine, Baltimore, MD, and Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, MD, E-mail: michael.sikorski@som.umaryland.edu. Glenn Fatupaito and Chandler Tuilagi, Tupua Tamasese Meaole Hospital, Ministry of Health, Government of Samoa, Apia, Samoa, E-mails: glenf@health.gov.ws and chandla21914@gmail.com. Siaosi Tupua, Robert Thomsen, Susana Nimarota-Brown, Linatupu Punimata, and Michelle Sialeipata, Samoa Typhoid Fever Control Program, Ministry of Health, Government of Samoa, Apia, Samoa, E-mails: siaosi.tupua@health.gov.ws, robertt@health.gov.ws, susana.brown@health.gov.ws, linatupu@gmail.com, and michelle.sialeipata@health.gov.ws. Savitra Rambocus, Samoa Typhoid Fever Control Program, Ministry of Health, Government of Samoa, Apia, Samoa, and Microbiological Diagnostic Unit Public Health Laboratory, Department of Microbiology and Immunology, The University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Melbourne, Australia, E-mail: savitra.rambocus@unimelb.edu.au. Jane Han, Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, MD, and Samoa Typhoid Fever Control Program, Ministry of Health, Government of Samoa, Apia, Samoa, Current affiliation: U.S. Agency for International Development Bureau for Humanitarian Assistance, Support Relief Group, WA, E-mail: janejhan@hotmail.com. Roy Robins-Browne, Microbiological Diagnostic Unit Public Health Laboratory, Department of Microbiology and Immunology, The University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Melbourne, Australia, and Murdoch Children’s Research Institute, Royal Children’s Hospital, Melbourne, Australia, E-mail: r.browne@unimelb.edu.au. Take Naseri, Samoa Typhoid Fever Control Program, Ministry of Health, Government of Samoa, Apia, Samoa, and Tupua Tamasese Meaole Hospital, Ministry of Health, Government of Samoa, Apia, Samoa, E-mail: ceo@health.gov.ws. Myron Levine, Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, MD, Department of Medicine, University of Maryland School of Medicine, Baltimore, MD, Department of Pediatrics, University of Maryland School of Medicine, Baltimore, MD, Samoa Typhoid Fever Control Program, Ministry of Health, Government of Samoa, Apia, Samoa, and Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, MD, E-mail: mlevine@som.umaryland.edu.

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