Serum and urine osmolality: 8 hours, 24 hours and 1-month sample stability.

OBJECTIVES: The body of literature varies significantly regarding serum and urine osmolality stability. Therefore, our aim was to investigate the stability of serum and urine osmolality at different temperatures (room temperature (RT) 4-8 °C, -20 °C) and time conditions (8 h, 24 h, 1 month). METHODS: The stability study was conducted following the CRESS guidelines, including 40 serum and urine samples. Samples were aliquoted into three aliquots and stored as follows: primary tube stored at RT for 8 h; two capped aliquots stored at 4-8 °C for 8 h and 24 h; one aliquot stored at -20 °C for 1 month. To minimize imprecision error, serum and urine osmolality were measured by the freezing point depression method in triplicate on OSMOMAT 3000 (Gonotech, Germany) analyzer. Percentage difference (PD%) against baseline measurement was calculated. Deviations were assessed against a reference change value of 5.0%. RESULTS: The PD% for serum and urine osmolality was below 2.0% for all time/temperature conditions. For serum samples: primary tube after 8 h at RT PD% (95% CI) = 0.0% (-0.3, 0.2%); 8 h at 4-8 °C PD% (95% CI) = -0.4% (-0.7, 0.0%); 24 h at 4-8 °C PD% (95% CI) = -0.7% (-0.7, -0.6%); 1 month at -20 °C PD% (95% CI) = -2.1% (-2.4, -1.5%). For urine samples: after 8 h at RT PD% (95% CI) =0.6% (0.2, 0.9%); 8 h at 4-8 °C PD% (95% CI) = -0.2% (-0.5, 0.1%); 24 h at 4-8 °C PD% (95% CI) = -0.2% (-0.5, 0.0%); 1 month at -20 °C PD% (95% CI) = -2.0% (-3.0, -1.0%). CONCLUSIONS: Changes in osmolality for tested conditions for serum and urine samples, were within acceptance criteria. Reflex and add-on osmolality testing can be performed within the same day in samples kept at RT for 8 h in primary tube and within 24 h, in aliquoted refrigerated samples, without compromising the reliability of test results. For longer storage, samples should be kept at -20 °C.

Haemoglobin A1c-based screening for prediabetes and diabetes mellitus: a multi-center study in Croatian adult population.

INTRODUCTION: Based on the hypothesis that there is a substantial rate of adults with prediabetes and undiagnosed diabetes mellitus (DM), our aim was to perform haemoglobin A1c (HbA1c)-based screening in a cohort of Croatian adults and estimate the prevalence of prediabetes and undiagnosed DM according to American Diabetes Association criteria. MATERIALS AND METHODS: This multi-center, cross-sectional study performed in six Croatian hospitals included 5527 patients aged 40 to 70 years admitted to the Emergency Department or undergoing a primary care check-up. Haemoglobin A1c was measured from leftover whole blood samples using the enzymatic method on either Alinity c or Architect c-series analyser (Abbott Laboratories, Chicago, USA). Haemoglobin A1c between 39-47 mmol/mol was classified as prediabetes, while ≥ 48 mmol/mol as undiagnosed DM. RESULTS: After exclusion of 435 patients with known DM, the final cohort included 5092 patients (median age 57; 56% males). A total of 882 (17.3%) patients had HbA1c values between 39 and 47 mmol/mol. There were 214 (4.2%) patients with HbA1c ≥ 48 mmol/mol. Prediabetes prevalence ranged from 14.2% to 20.5%, while undiagnosed DM from 3.3% to 7.3%, with statistically significant differences among settings (P < 0.001). Age-stratified analysis showed that prediabetes and undiagnosed DM prevalence increase with age (P < 0.001), being 25.4% and 5.8%, respectively, in patients aged 60 to 70 years. CONCLUSION: Underlying impairment of glucose metabolism was identified in about one in five adults, with significant number of patients with already overt DM. These results should serve as a starting point for further steps directed towards promotion of preventive measures for DM in Croatia.