Erythrocyte Na+/Li+ countertransport and Na+/K+-2Cl(-) co-transport measurement in essential hypertension: Useful diagnostic tools or failure? A meta-analysis of 17 years of literature

1 A meta-analysis of 17 years of literature on erythrocyte Na+/Li+ countert ransport (NLCT) and Na+/K+ co-transport (COT) measurements in relation to e ssential hypertension is presented. The analysis aimed to answer two questi ons: (i) Which clinical or laboratory variables influence NLCT and COT flux values i (ii) How useful are NLCT and COT measurements as a diagnostic aid in essential hypertension 2. Regression analysis was performed on the mean flux values and relevant c linical and laboratory values. Studies in both normotensive and hypertensiv e subjects were stratified for variables which showed a significant associa tion with the measured flux. For hypertensive subjects the studies were als o stratified for medication. Means of strata were calculated after weighing the mean of a study by the inverse of its own variance and were compared i n normotensive as well as hypertensive subjects using a t-test. 3. The analysis did not demonstrate systematic effects of laboratory variab les for either NLCT or GOT. It was found that essential hypertension, famil y history of hypertension, gender and antihypertensive medication are main determinants for the flux values of both transport systems. After stratific ation for these determinants, significant differences in weighed mean flux values between normotensive and hypertensive subjects were demonstrated. Ho wever, these differences are much smaller than the variance in the weighed mean flux values, suggesting the existence of other unknown variables that strongly affect the flux rates. 4. In conclusion, NLCT and COT measurements cannot be of diagnostic use in essential hypertension.