A predictive tool for an effective use of 18F-FDG PET in assessing activity of sarcoidosis
1 Department of Respiratory Medicine, Atrium Medical Centre, Heerlen, The Netherlands
2 Department of Epidemiology, University Maastricht, Maastricht, The Netherlands
3 Department of Radiology, University Hospital Gasthuisberg, Leuven, Belgium
4 Department of Nuclear Medicine, Maastricht University Medical Centre, Maastricht, The Netherlands
5 Department of Clinical Chemistry, Maastricht University Medical Centre, Maastricht, The Netherlands
6 Faculty of Health, Medicine and Life Sciences, University Maastricht, The Netherlands and Department of interstitial lung diseases, Hospital Gelderse Valley, Ede, The Netherlands
7 Faculty of Health, Medicine and Life Sciences; UNS 40 room 4.550, University Maastricht The Netherlands, PO Box 3100, 6202 NC, Maastricht, The Netherlands
BMC Pulmonary Medicine 2012, 12:57 doi:10.1186/1471-2466-12-57Published: 14 September 2012
18F-FDG PET/CT (PET) is useful in assessing inflammatory activity in sarcoidosis. However, no appropriate indications are available. The aim of this study was to develop a prediction rule that can be used to identify symptomatic sarcoidosis patients who have a high probability of PET-positivity.
We retrospectively analyzed a cohort of sarcoidosis patients with non organ specific persistent disabling symptoms (n = 95). Results of soluble interleukin-2 receptor (sIL-2R) assessment and high-resolution computed tomography (HRCT) were included in the predefined model. HRCT scans were classified using a semi-quantitative scoring system and PET findings as positive or negative, respectively. A prediction model was derived based on logistic regression analysis. We quantified the model’s performance using measures of discrimination and calibration. Finally, we constructed a prediction rule that should be easily applicable in clinical practice.
The prediction rule showed good calibration and good overall performance (goodness-of-fit test, p = 0.78, Brier score 20.1%) and discriminated between patients with positive and negative PET findings (area under the receiver-operating characteristic curve, 0.83). If a positive predictive value for the presence of inflammatory activity of ≥90% is considered acceptable for clinical decision-making without referral to PET, PET would be indicated in only 29.5% of the patients. Using a positive predictive value of 98%, about half of the patients (46.3%) would require referral to PET.
The derived and internally validated clinical prediction rule, based on sIL-2R levels and HRCT scoring results, appeared to be useful to identify sarcoidosis patients with a high probability of inflammatory activity. Using this rule may enable a more effective use of PET scan for assessment of inflammatory activity in sarcoidosis.