Antepartum prediction of respiratory distress syndrome: a comparison of the shake test, the tap test and the turbidity test

The shake test, the tap test and the turbidity test were evaluated to determine their accuracy in predicting lung function maturity, ie their ability to predict respiratory distress syndrome (RDS). The turbidity test was the most efficient with a sensitivity of 60%, a specificity of 97%, a positive predictive value of 82% and a negative predictive value of 92%. The shake test had a sensitivity of 40%, a specificity of 95%, a positive predictive value of 63% and a negative predictive value of 88%. The tap test at 2 minutes had a sensitivity of 57%, a specificity of 78%, a positive predictive value of 35% and a negative predictive value of 89%. It was fortuitous that the simplest and cheapest test was found to be the most efficient test of the three. We recommend that the turbidity test or at least one of these tests should be used to determine the maturity of lung function when non-urgent elective deliveries are contemplated, to help reduce the incidence of RDS in this group of patients.