Data about the value of erosions detected by other new imaging modalities such as sonography or magnetic resonance imaging (MRI) in UA population are scarce.
Relatively good agreement was obtained between predicted and measured values of erosion rates for each of the prediction models (R2 = 0.86**, and R2 = 0.90**).
At the subject level, the kappa values for EE (0.73, 95% CI 0.63 to 0.84) and for BF (0.63, 95% CI 0.53 to 0.73) indicated substantial agreement comparable to the kappa values of erosion and BME.
Duer and colleagues investigated the value of MRI erosions in UA patients without erosions at conventional radiography and found that the presence of MRI erosions has a PPV of 50%, a NPV of 85%, a LR+ of 2.7 and a LR- of 0.5 for prediction of RA development [ 19].
Mundwiler and colleagues set out primarily to determine the sensitivity, specificity, and predictive value of MRI erosions at individual metatarsophalangeal (MTP) joints for the development of new XR erosions after 6, 12, and 24 months.
In addition, the Reynolds number (i.e. flow regime) played a more significant role in controlling the value of the erosion-corrosion rate rather than the sand concentration.
In contrast, the prognostic value of baseline erosions for the disease outcome in UA is unknown.
Tamai and colleagues studied the predictive value of MRI erosions (without knowledge if these were radiographically visible) and observed a PPV of 81.5%, a NPV of 48%, a LR+ of 3.18 and a LR- of 0.78 [ 20].
This yields an erosion rate (1968 2009) of 151.8 Mg (MT) ha− 1 y− 1, which matches well typical values for erosion of mined areas, commonly above 100 Mg (MT) ha− 1 y− 1.
The values of avoided erosion through afforestation and the other ecosystem services that forestry provides have been quantified (Barry et al. [2014]) but these services are currently not reflected by market prices in New Zealand.
