Evaluation of three prediction formulas of 24-hour urinary sodium excretion in Chinese residents: a systematic review and meta-analysis.

OBJECTIVE: To determine the appropriateness of three widely used formulas estimating 24-h urinary Na (24hUNa) from spot urine samples in the Chinese population. DESIGN: Systematic review and meta-analysis. SETTING: Literature review was conducted to identify studies for estimating 24hUNa using the Kawasaki, Tanaka and INTERSALT formulas simultaneously in PubMed, Embase and the Cochrane library databases. The mean difference (MD) and correlation coefficients (r) between measures and estimates from different formulas were assessed. PARTICIPANTS: Information extraction and quality assessment were performed in thirteen studies involving 8369 subjects. RESULTS: Two studies which affected the overall robustness were excluded in the 'leave-one-out' sensitivity analyses. Within the final meta-analysis included eleven studies and 7197 participants, 36·07 mmol/d (95 %CI 16·89, 55·25) of MD was observed in the Kawasaki formula, and -19·62 mmol/d (95 %CI -37·37, -1·87) in the Tanaka formula and -35·78 mmol/d (95 %CI -50·76, -20·80) in the INTERSALT formula; a pooled r-Fisher's Z of 0·39 (95 %CI 0·32, 0·45) in the Kawasaki formula, 0·43 (95 %CI 0·37, 0·49) in the Tanaka formula and 0·36 (95 %CI 0·31, 0·42) in the INTERSALT formula. Subgroup analyses were conducted to explore the possible factors affecting the accuracy of the formula estimation from three mainly aspects: population types, Na intake levels and urine specimen types. CONCLUSIONS: The meta-analysis suggested that the Tanaka formula performed a more accurate estimate in Chinese population. Time of collecting spot urine specimens and Na intake level of the sample population might be the main factors affecting the accuracy of the formula estimation.

Effect of salt substitute and antihypertensive medications among high cardiovascular risk patients: A sub-study of Salt Substitute and Stroke Study (SSaSS).

The relationship between the differential protective effect of salt substitute between hypertensive and normotensive individuals and the use of cardiovascular medications remains unclear. This study involved 4211 individuals with a history of stroke or hypertension who participated in the Salt Substitute and Stroke Study (SSaSS) from 120 villages in Shanxi Province. The aim of this study was to investigate the differences in major adverse cardiovascular events and blood pressure changes between the salt substitute and the regular salt group in the subgroups of participants taking different antihypertensive medications. Mixed models were employed and adjusted for the cluster effect (village) and potential confounding variables. During the average follow-up period of 4.66 years, a significantly protective effect of salt substitute on reducing the risk of cardiovascular events was observed in the participants who taking antihypertensive medications (rate ratio: 0.81, 95% CI: 0.68 to 0.95. p = 0.011), whereas no significant effect in participants not taking antihypertensive medications (rate ratio: 0.91, 95% CI: 0.62 to 1.32, p = 0.612). Significant effects to lower systolic blood pressure of the salt substitutes were observed in the participants who took different antihypertensive medications. This study emphasized that the use of salt substitutes might enhance the efficacy of anti-hypertensive medications in lowering blood pressure and reducing the risk of adverse cardiovascular events.

A Method for Estimating 24 h Urinary Sodium and Potassium Excretion by Spot Urine Specimen in Stroke Patients.

Spot urine specimens have been used to estimate 24 h urinary sodium (Na) excretion (24UNaV) and potassium (K) excretion (24UKV). However, the validity is limited for 24UNaV and unknown for 24UKV in stroke patients, using the existing formulas. Herein, we developed and validated a new formula for 24UNaV and 24UKV by spot urine specimens in stroke patients. Spot and 24 h urine samples were collected from 970 stroke patients. The models of 24UNaV and 24UKV were developed using stepwise multivariate linear regression in 689 patients. The performance of different formulas was internally validated in 281 patients at the population and individual levels. The obtained new formulas were: (1) estimated 24UNaV (mmol/day): -0.191 × Age + 4.349 × BMI + 0.229 × SpotNa + 1.744 × SpotNa/Spot creatinine (Cr) + 41.492 (for male); -1.030 × Age + 2.011 × BMI + 0.143 × SpotNa + 1.035 × SpotNa/SpotCr + 147.159 (for female); and (2) estimated 24UKV (mmol/day): -0.052 × Age + 0.410 × BMI + 0.031 × SpotK + 33.280 × Ln (spotK/spot Cr) - 5.789 × Ln (spotNa/spot Cr) - 1.035 (for male); -0.235 × Age + 0.530 × BMI + 0.040 × SpotK + 30.990 × Ln (spot K/spot Cr) - 7.837 × Ln (spotNa/spotCr) + 4.318 (for female). The new formula obtained the lowest mean bias (5.17 mmol/day for 24UNaV and 0.85 mmol/day for 24UKV) and highest proportion at the cutoff under the ±30% level for the estimation of 24UNaV (59.43%) and 24UKV (70.11%). The new formula provides a meaningful exploration to estimate 24UNaV and 24UKV in stroke patients by using spot urine specimens.