"Background: optimal hydration represents adequate total daily fluid intake to compensate for daily water losses, ensure adequate urine output to reduce the risk of urolithiasis and renal function decline, and also avoid the production of arginine vasopressin (AVP). Twenty four hour urine osmolality has been used to assess hydration status, but it is challenging because of the possibility of spilling urine and limitation of daily activities. This study is aimed to determine the performance of the afternoon urine osmolality to assess the optimal hydration status compared with 24 hour urine osmolality.
Methods: a cross sectional study was conducted on healthy employees aged 18-59 years at Universitas Indonesia Medical Faculty/Cipto Mangunkusumo Hospital, with consecutive sampling method. The ROC curve was analyzed to obtain the optimal cut off point and the accuracy of the afternoon urine osmolality in assessing the optimal hydration status.
Results: between August-September 2016 there were 120 subjects (73.8% female, median age 32 years) who met the study criteria with a median 24 hour urine osmolality 463.5 (95% CI, 136-1427) mOsm/kg H2O and median afternoon urine osmolality 513 (95% CI, 73-1267). We found moderate correlation (r=0.59; p<0.001) between afternoon urine osmolality and a 24 hour urine osmolality. Using ROC curve, the AUC value was 0.792 (95% CI, 0.708-0.875) with the cut off 528 mOsm/kg H2O. To assess the optimal hydration status, the afternoon urine osmolality had the sensitivity of 0.7 (95% CI, 0.585-0.795) and the specificity of 0.76 (95% CI, 0.626-0.857), Likelihood Ratio (LR) (+) 2.917 (95% CI, 1.74-4.889) and LR (-) 0.395 (95% CI, 0.267-0.583).
Conclusion: afternoon urine osmolality can be used as a diagnostic tool to assess the optimal hydration status in healthy population with cut off 528 mOsm/kg H2O, sensitivity of 0.7, and specificity of 0.76.
Latar belakang: hidrasi optimal merupakan hidrasi yang dianggap cukup untuk menggantikan kehilangan cairan, menjamin produksi urin adekuat untuk mengurangi risiko urolitiasis dan penurunan fungsi ginjal, serta mencegah keluarnya arginin vasopresin (AVP). Osmolalitas urin 24 jam diketahui dapat mengukur status hidrasi seseorang, namun dirasakan memberatkan karena kemungkinan urin tercecer dan membatasi aktivitas kerja. Penelitian ini bertujuan mengetahui peranan pemeriksaan osmolalitas urin sewaktu sore hari untuk menilai status hidrasi optimal. Metode: studi potong lintang dilakukan pada karyawan sehat berusia 18-59 tahun di lingkungan FKUI/RSUPN Cipto Mangunkusumo, memakai metode consecutive sampling. Dilakukan analisis kurva ROC untuk mendapatkan titik potong dan akurasi osmolalitas urin sore hari dalam menilai status hidrasi optimal.Hasil:antara bulan Agustus-September 2016 terkumpul 120 subjek (73,8% perempuan, median usia 32 tahun) yang memenuhi kriteria penelitian dengan median osmolalitas urin 24 jam 463,5 (95% IK, 136-1427) mOsm/kg H2O dan median osmolalitas urin sore hari 513 (95% IK, 73-1267) mOsm/kg H2O. Pada analisis didapatkan korelasi sedang (r=0,59; p<0,001) antara osmolalitas urin sore hari dengan osmolalitas urin 24 jam. Dengan kurva ROC didapatkan nilai AUC 0,792 (95% IK, 0,708-0,875) dengan titik potong 528 mOsm/kg H2O. Dalam menentukan hidrasi optimal, osmolalitas urin sore hari memiliki sensitivitas sebesar 0,7 (95% IK, 0,585-0,795) dan spesifisitas 0,76 (95% IK, 0,626-0,857) serta Likelihood Ratio (LR) (+) 2,917 (95% IK, 1,74-4,889) dan LR (-) 0,395 (95% IK, 0,267-0,583). Kesimpulan: osmolalitas urin sore hari dapat menjadi indikator dalam menilai status hidrasi optimal pada populasi sehat dengan titik potong 528 mOsm/kg H2O serta sensitivitas 0,7 dan spesifisitas 0,76."
Jakarta: Faculty of Medicine University of Indonesia, 2017