The Neutral Red Test - A comparison with the Insulin Test in 100 patients with duodenal ulcer treated by truncal vagotomy and pyloroplasty.

Over a period of nineteen years, one hundred patients were initially tested with the Neutral Red Test and with the Insulin Test. Twenty one patients died during the study, the main cause of death being cancer and cerebro-vascular disease. No increase in cancer of the stomach or colon was noted during the study. Sixty five patients were available for study (mean follow-up time - fourteen years, six months. The clinical outcome showed an 81.5% in the "successful outcome" (Visick I and II). The recurrence rate was 14%, the majority of these being treated medically. The study confirms the simplicity and safety of the Neutral Red Test with its ability to stimulate the vagal system centrally and thus produce a mild secretagogue effect. The Neutral Red Test confirms many of the features of the Insulin Test and there is a very high degree of agreement between the two tests. The classification of the Insulin Test into "early" and "late" is confirmed. The predictive value of these tests is relatively low but has clinical value. The fate of the "late" positive response is similar to the negative response. Therefore, the "late" positive response carries a good prognosis as far as future clinical outcome is concerned. Therefore, the ability of a few residual vagal fibres to re-innervate the gastric mucosa by collateral nerve regeneration or sprouting is insignificant, even over a long period of time. Therefore, this study makes a strong plea for maintaining or re-introducing tests to assess the completeness of vagotomy post-operatively in order to prognosticate clinical outcome and to assess the vagotomist.