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1.  Added value of cost-utility analysis in simple diagnostic studies of accuracy: 18F-fluoromethylcholine PET/CT in prostate cancer staging 
Diagnostic studies of accuracy targeting sensitivity and specificity are commonly done in a paired design in which all modalities are applied in each patient, whereas cost-effectiveness and cost-utility analyses are usually assessed either directly alongside to or indirectly by means of stochastic modeling based on larger randomized controlled trials (RCTs). However the conduct of RCTs is hampered in an environment such as ours, in which technology is rapidly evolving. As such, there is a relatively limited number of RCTs. Therefore, we investigated as to which extent paired diagnostic studies of accuracy can be also used to shed light on economic implications when considering a new diagnostic test. We propose a simple decision tree model-based cost-utility analysis of a diagnostic test when compared to the current standard procedure and exemplify this approach with published data from lymph node staging of prostate cancer. Average procedure costs were taken from the Danish Diagnosis Related Groups Tariff in 2013 and life expectancy was estimated for an ideal 60 year old patient based on prostate cancer stage and prostatectomy or radiation and chemotherapy. Quality-adjusted life-years (QALYs) were deduced from the literature, and an incremental cost-effectiveness ratio (ICER) was used to compare lymph node dissection with respective histopathological examination (reference standard) and 18F-fluoromethylcholine positron emission tomography/computed tomography (FCH-PET/CT). Lower bounds of sensitivity and specificity of FCH-PET/CT were established at which the replacement of the reference standard by FCH-PET/CT comes with a trade-off between worse effectiveness and lower costs. Compared to the reference standard in a diagnostic accuracy study, any imperfections in accuracy of a diagnostic test imply that replacing the reference standard generates a loss in effectiveness and utility. We conclude that diagnostic studies of accuracy can be put to a more extensive use, over and above a mere indication of sensitivity and specificity of an imaging test, and that health economic considerations should be undertaken when planning a prospective diagnostic accuracy study. These endeavors will prove especially fruitful when comparing several imaging techniques with one another, or the same imaging technique using different tracers, with an independent reference standard for the evaluation of results.
PMCID: PMC4396007  PMID: 25973339
Diagnostic study; accuracy study; sensitivity; specificity; cost-effectiveness; molecular imaging; positron-emission tomography/computed tomography; 18F-fluoromethylcholine; prostate cancer; staging
2.  PET/CT in the diagnosis of inflammatory bowel disease in pediatric patients: a review 
The literature on positron emission tomography and computed tomography using 18fluoro-deoxyglusose (FDG-PET/CT) in the diagnosis of pediatric inflammatory bowel disease (IBD) is presented. Only five papers representing independent studies were identified and included in this review. Of these, two studies dealt with both stand-alone FDG-PET and FDG-PET/CT, while three were about stand-alone FDG-PET only. No studies could be found that focused on FDG-PET/CT only. The five studies comprised analysis of a total 181 pediatric patients (0-18 years of age). They unanimously indicated that FDG-PET/CT is a versatile method with a diagnostic high sensitivity ranging from 70% to 97%. In conclusion, the pediatric literature on FGD-PET/CT’s role in the diagnosis of IBD is very limited. Prospective studies of well characterized populations are needed in order to validate this novel imaging modality in pediatric IBD.
PMCID: PMC3999402  PMID: 24795836
Inflammatory bowel disease; ulcerative colitis; Crohn’s disease; positron-emission tomography and computed tomography
3.  FDG-PET/CT can rule out malignancy in patients with vocal cord palsy 
The aim was to investigate the performance of 18F-fluorodeoxyglucose PET/CT to rule out malignancy in patients with confirmed vocal cord palsy (VCP). Between January 2011 and June 2013, we retrospectively included consecutive patients referred to PET/CT with paresis or paralysis of one or both vocal cords. PET/CT results were compared to clinical workup and histopathology. The study comprised 65 patients (32 females) with a mean age of 66±12 years (range 37-89). Eleven patients (17%) had antecedent cancer. Twenty-seven (42%) were diagnosed with cancer during follow-up. The palsy was right-sided in 24 patients, left-sided in 37, and bilateral in 4. Median follow-up was 7 months (interquartile range 4-11 months). Patients without cancer were followed for at least three months. PET/CT suggested a malignancy in 35 patients (27 true positives, 8 false positives) and showed none in 30 (30 true negatives, 0 false negatives). Thus, the sensitivity, specificity, positive and negative predictive values, and accuracy were (95% confidence intervals in parenthesis): 100% (88%-100%), 79% (64%-89%), 77% (61%-88%), 100% (89%-100%), and 88% (78%-94%), respectively. Sixteen patients had palliative treatment, while 11 were treated with curative intent, emphasising the severity of VCP and the need for a rapid and accurate diagnostic work-up. In this retrospective survey, biopsy proven malignancy (whether newly diagnosed or relapsed) was the cause of VCP in almost half of patients (42%). PET/CT had a high sensitivity (100%) with a relatively high false positive rate, but was excellent in ruling out malignancy (negative predictive value 100%).
PMCID: PMC3992212  PMID: 24753985
FDG-PET/CT; palsy; paresis; paralysis; vocal cord; laryngeal nerve
4.  Interim analyses in diagnostic versus treatment studies: differences and similarities 
The purpose of this paper was to contrast interim analyses in (randomized controlled) treatment studies with interim analyses in paired diagnostic studies of accuracy with respect to planning and conduct. The term ‘treatment study’ refers to a (randomized) clinical trial that aims to demonstrate the superiority or noninferiority of one treatment compared with another, and the term ‘diagnostic study’ to a clinical study that compares two diagnostic procedures, using a third diagnostic procedure as the gold standard. Though interim analyses in treatment studies and paired diagnostic studies show similarities in a priori planning of timing, decision rules, and the consequences of the analyses, they differ with respect to (1) the need for sample size adjustments, (2) the possibility of early decisions without early stopping, and (3) the impact of keeping results secret. These differences are due, respectively, to certain characteristics of paired diagnostic studies: the dependence of the sample size on the agreement rate between the modalities, multiple aims of diagnostic accuracy studies, and the advantages of early unblinding of results at the individual level. We exemplified our points by using a recent investigation at our institution on the detection of bone metastases from prostate cancer in patients with histologically confirmed prostate cancer in which 99mTc-MDP whole body bone scintigraphy was compared to positron emission tomography/computed tomography with 18F-fluorocholine as tracer, using magnetic resonance imaging as a reference.
PMCID: PMC3477734  PMID: 23133821
Study design; diagnostic imaging; PET/CT; efficacy studies; accuracy studies; sample size
5.  How to study optimal timing of PET/CT for monitoring of cancer treatment 
The use of PET/CT for monitoring treatment response in cancer patients after chemo- or radiotherapy is a very promising approach to optimize cancer treatment. However, the timing of the PET/CT-based evaluation of reduction in viable tumor tissue is a crucial question. We investigated how to plan and analyze studies to optimize this timing.
General considerations about studying the optimal timing are given and four fundamental steps are illustrated using data from a published study.
The optimal timing should be examined by optimizing the schedule with respect to predicting the overall individual time course we can observe in the case of dense measurements. The optimal timing needs not to and should not be studied by optimizing the association with the prognosis of the patient.
The optimal timing should be examined in specific ‘schedule optimizing studies’. These should be clearly distinguished from studies evaluating the prognostic value of a reduction in viable tumor tissue.
PMCID: PMC3477720  PMID: 23133795
cancer; response evaluation; prognostic value; optimal schedule

Results 1-5 (5)