title: Correlation between the clinical pretest probability score and the lung ventilation and perfusion scan probability.
abstract: OBJECTIVE
  Aim of the study was to determine the accuracy of the clinical pretest probability (PTP) score and its association with lung ventilation and perfusion (VQ) scan.
  
  
  METHODS
  A retrospective analysis of 510 patients who had a lung VQ scan between 2008 and 2010 were included in the study. Out of 510 studies, the number of normal, low, and high probability VQ scans were 155 (30%), 289 (57%), and 55 (11%), respectively.
  
  
  RESULTS
  A total of 103 patients underwent computed tomography pulmonary angiography (CTPA) scan in which 21 (20%) had a positive scan, 81 (79%) had a negative scan and one (1%) had an equivocal result. The rate of PE in the normal, low-probability, and high-probability scan categories were: 2 (9.5%), 10 (47.5%), and 9 (43%) respectively. A very low correlation (Pearson correlation coefficient r = 0.20) between the clinical PTP score and lung VQ scan. The area under the curve (AUC) of the clinical PTP score was 52% when compared with the CTPA results. However, the accuracy of lung VQ scan was better (AUC = 74%) when compared with CTPA scan.
  
  
  CONCLUSIONS
  The clinical PTP score is unreliable on its own; however, it may still aid in the interpretation of lung VQ scan. The accuracy of the lung VQ scan was better in the assessment of underlying pulmonary embolism (PE).
authors.affiliation: Department of Nuclear Medicine, King's College Hospital NHS Foundation Trust, Denmark Hill, London, United Kingdom.
authors.forename: Shanmugasundaram
authors.initials: S
authors.lastname: Bhoobalan
authors.affiliation: Department of Nuclear Medicine, King's College Hospital NHS Foundation Trust, Denmark Hill, London, United Kingdom.
authors.forename: Riddhika
authors.initials: R
authors.lastname: Chakravartty
authors.affiliation: Department of Medical Imaging, Canterbury Christ Church University, Canterbury, Kent, United Kingdom.
authors.forename: Gill
authors.initials: G
authors.lastname: Dolbear
authors.affiliation: Department of Nuclear Medicine, King's College Hospital NHS Foundation Trust, Denmark Hill, London, United Kingdom.
authors.forename: Mazin
authors.initials: M
authors.lastname: Al-Janabi
keywords: Pretest probability score; pulmonary embolism; ventilation and perfusion