Studies of diagnostic accuracy are the most commonly performed diagnostic tests. These are carried out by using Decision Matrix tables in which sensitivities, specificities, predictive values and other ratios are calculated and compared. Various recoverable pitfalls and limitations of this method have been reported. This study reports additional further limitations of using this method as a statistical analytical tool. Decision protocol and formulae are presented to show how the sensitivities and specificities of tests are compared in order to make a decision. The study also shows how special tables can be constructed for the four results of comparative diagnostic tests (true positive, true negative, false positive and false negative), and cautions against the use of some 2 x 2 contingency tables. The procedures of how to use these special tables and formulae for comparing sensitivity and specificity and deriving confidence intervals for their difference are presented. It is also shown how it is possible to make a single inference from diagnostic test performance which will permit the determination of which test is better.

Congenital para-oesophageal hiatal hernia (PEHH) is a rare problem in infancy, however, it constitutes a clinical entity that mandates surgical repair once the diagnosis is made. In the paediatric age group, acquired PEHH has been described as a major complication in a number of patients who were treated surgically for gastro-oesophageal reflux (GER) by Nissen fundoplication. PEHH is a frequently encountered condition in elderly patients; it accounts for 5% of diaphragmatic hiatal hernias. In both paediatric and adult patients PEHH, whether congenital or acquired in origin, is usually associated with potentially lethal complications such as gastric volvulus, incarceration, and perforation. In clinical practice true PEHH is extremely rare. The term has been expanded to include large gastric hiatal hernias where most of the stomach and the gastro-oesophageal junction are in the chest. Six infants with congenital PEHH are presented, together with an attempt to understand its possible aetiology and a review of its current surgical management.

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