Accuracy of hepatobiliary scintigraphy and added value of SPECT/CT versus planar imaging for diagnosing biliary atresia

OBJECTIVE: Hepatobiliary scintigraphy (HBS) is an important tool in diagnosing biliary atresia in infants. There is limited evidence on the use of single photon emission computed tomography/computed tomography (SPECT/CT) as an additional imaging method to planar imaging. We evaluated the value of SPECT/CT in unclear cases of planar HBS.

SUBJECTS AND METHODS: Consecutive patients with suspected biliary atresia who underwent guideline-compliant HBS from January 2010 until March 2020 were reviewed, and cases with SPECT/CT were identified. Each step within the imaging procedure (dynamic, static [early and late], and SPECT/CT) was blindly reread in consensus by two observers and categorized based on a 5-point scale: 0, definitely no bowel excretion (i.e., atresia confirmed); 1, probably positive; 2,equivocal; 3, probably negative; and 4, definite negative (i.e., atresia not confirmed). In this analysis, categories were dichotomized as negative for biliary atresia (scores 3-4) or positive (scores 0-2, including equivocal scans). Available follow-up information constituted the standard of truth (SoT).

RESULTS: Twenty-three infants had HBS, among which ten (4 boys and 6 girls; mean age 36 days; range 8-108) underwent SPECT/CT. Single photon emission computed tomography SPECT/CT was performed as early examination (<8h) in 3 subjects and late (8 to 24 h) in 7 infants. Reread SPECT/CT was categorized as positive for atresia in three infants and negative in seven infants. The SoT showed biliary atresia in one of ten patients. Single photon emission computed tomography/CT was true positive in one case, false positive in two, and true negative in seven. No false negative cases were noted. The diagnostic performance of SPECT/CT showed a sensitivity of 100%, specificity of 78%, positive predictive value (PPV) of 33%, negative predictive value (NPV) of 100%, and accuracy of 90%. For comparison, the diagnostic performance of planar HBS showed a sensitivity of 100%, specificity of 67%, PPV of 25%, NPV of 100%, and accuracy of 70%. In summary, the addition of SPECT/CT to planar HBS improved specificity andaccuracyand marginally improved PPV. Single photon emission computed tomography/CT provided more confidence in the final conclusion in 8/10 patients. In the remaining two cases, SPECT/CT did not improve the level of confidence (one remained equivocal, and one changed from probably no excretion to equivocal).

CONCLUSION: These preliminary data demonstrated increased accuracy of add-on SPECT to planar HBS predominantly due to improved specificity. This finding is consistent with the existing but limited literature and supports the recommendation of routine use of SPECT/CT or SPECT.