Eighteen studies were included in the review, from which 25 2x2tables were generated. The total number of participants could not be derived from the data shown.

The meta-regression found that assessment of lymph node detection was associated with a significant change in DOR. Therefore, summary results were presented separately for lymph node and patient level data. However, the authors appear to have drawn their conclusions from the latter. The results were presented using pre-test disease probabilities of 20, 40 and 60%. Those for 20% and 60% are summarised below. The Galbraith plots showed no evidence of heterogeneity between the studies.

For primary diagnosis, positive and negative LRs were 3.90 (95% confidence interval, CI: 2.56, 5.93) and 0.24 (95% CI: 0.14, 0.41), respectively. For restaging (recurrence assessment), the positive LR used was 3.96 (95% CI: 2.79, 5.63) and the negative LR was 0.16 (95% CI: 0.10, 0.25).

Using a 20% pre-test disease probability, a meta-analysis of patient level data for primary diagnosis showed positive and negative post-test probabilities of 49.4% and 5.7%, respectively. For restaging (recurrence assessment) the positive and negative post-test probabilities were 49.7% and 3.8%, respectively. Those for lymph node level data for primary diagnosis were 81.2% and 4.5% respectively. For restaging, the results were 73.3% and 3.4%.

Given the results for negative post-test probabilities in patient level data, the authors suggested that (in patients with low pre-test probability) the FDG PET test was able to rule out disease with approximately 6% post-test disease probability. Therefore, further imaging could be suspended.

Using a 60% pre-test disease probability, a meta-analysis of patient level data for primary diagnosis showed positive and negative post-test probabilities of 85.4% and 26.5%, respectively. For restaging, the positive and negative post-test probabilities were 85.6% and 19.4%, respectively. Those for lymph node level data for primary diagnosis were 96.3% and 22.2%. For restaging, the results were 94.3% and 17.4%.

Given the higher results for positive post-test probabilities in patient level data, the authors suggested that (in patients with higher pre-test probability) the FDG PET test would be considered accurate enough to start or modify treatment.

The authors advised cautious interpretation of the results, given the possibility of inconsistent LRs at different pre-test values. Observer agreement at the data extraction stage was 90 to 100%, with kappa values ranging from 0.9 to 1.0.