Basic and translational research provides the opportunity to evaluate variables that may be difficult to examine thoroughly with clinical populations.
In epidemiological studies, even with a moderate number of covariates, it is typically difficult to examine all possible interactions with standard regression techniques, because estimating a large number of parameters is required, and model selection quickly becomes cumbersome.
Isolated cDNA of At4g26540 in this report showed a structure with slight difference from the prediction in database, which made it difficult to examine the sequence difference with variant-specific primers.
As MDCT angiography is now well-established as the method of choice for the diagnosis of most of the different arterial pathological conditions in the abdomen [ 4], it would have been difficult to examine all included patients with an additional intra-arterial DSA for the purposes of our study.
Amongst the disadvantages of US are the facts that the examination is operator dependent and not reproducible and that it is difficult to examine the whole GI tract, with additional difficulties in obese children and in case of gas fullness of the bowel.
However, this study does provide an excellent assessment of the outcomes of amputees, which would be difficult to examine today given the infrequency with which amputations are performed for paediatric lower extremity bone tumours.
Since protein C is synthesized almost exclusively by the liver, it is difficult to examine this parameter in patients with severe sepsis, but animal models of sepsis can offer unique insights.
One of the reasons for this may be a higher contamination of non-tumour cells in the biopsies from the PSCC patients, which are much more difficult to examine and perform biopsies from, compared with oral cavity cancers, which normally present themselves as a clear visible tumour easy to distinguish from surrounding structures.
The implant obscures some of the parenchyma, and breasts with subglandular positioned implants with capsular contracture are the most difficult to examine (Carlson et al, 1993).
As with this study, it is often difficult to examine predictors of enrolment as ethics requirements prevent information being collected on individuals invited who decline to participate.
