An International Study of Interobserver Variability of “String Sign” of Pancreatic Cysts Among Experienced Endosonographers

Authors

Seifeldin Hakim
Emmanuel Coronel
Graciela M Nogueras González
Philip S Ge
Suresh T Chari
Nirav Thosani
Srinivas Ramireddy
Ricardo Badillo
Tomas DaVee
Marc F Catalano
Robert J Sealock
Sreeram Parupudi
Lyndon V Hernandez
Virendra Joshi
Atsushi Irisawa
Surinder Rana
Sundeep Lakhtakia
Peter Vilmann
Adrian Saftoiu
Siyu Sun
Marc Giovannini
Matthew H Katz
Michael P Kim
Manoop S Bhutani

Publication Date

1-1-2021

Journal

Endoscopic Ultrasound

DOI

10.4103/eus.eus_73_20

PMID

33473044

PMCID

PMC7980687

PubMedCentral® Posted Date

1-20-2021

PubMedCentral® Full Text Version

Post-print

Published Open-Access

yes

Keywords

mucinous pancreatic cyst, mucous, pancreatic cyst, string sign, surface tension, viscosity

Abstract

BACKGROUND AND OBJECTIVES: No single optimal test reliably determines the pancreatic cyst subtype. Following EUS-FNA, the "string sign" test can differentiate mucinous from nonmucinous cysts. However, the interobserver variability of string sign results has not been studied.

METHODS: An experienced endosonographer performed EUS-FNA of pancreatic cysts on different patients and was recorded on video performing the string sign test for each. The videos were shared internationally with 14 experienced endosonographers, with a survey for each video: "Is the string sign positive?" and "If the string sign is positive, what is the length of the formed string?" Also asked "What is the cutoff length for string sign to be considered positive?" Interobserver variability was assessed using the kappa statistic (κ).

RESULTS: A total of 112 observations were collected from 14 endosonographers. Regarding string sign test positivity, κ was 0.6 among 14 observers indicating good interrater agreement (P < 0.001) while κ was 0.38 when observers were compared to the index endosonographer demonstrating marginal agreement (P < 0.001). Among observations of the length of the string in positive samples, 89.8% showed >5 mm of variability (P < 0.001), indicating marked variability. There was poor agreement on the cutoff length for a string to be considered positive.

CONCLUSION: String sign of pancreatic cysts has a good interobserver agreement regarding its positivity that can help in differentiating mucinous from nonmucinous pancreatic cysts. However, the agreement is poor on the measured length of the string and the cutoff length of the formed string to be considered a positive string sign.