Establishment of reference intervals of clinical chemistry analytes for the adult population in Saudi Arabia: a study conducted as a part of the IFCC global study on reference values.

BACKGROUND: This study is a part of the IFCC-global study to derive reference intervals (RIs) for 28 chemistry analytes in Saudis. METHOD: Healthy individuals (n=826) aged ≥18 years were recruited using the global study protocol. All specimens were measured using an Architect analyzer. RIs were derived by both parametric and non-parametric methods for comparative purpose. The need for secondary exclusion of reference values based on latent abnormal values exclusion (LAVE) method was examined. The magnitude of variation attributable to gender, ages and regions was calculated by the standard deviation ratio (SDR). Sources of variations: age, BMI, physical exercise and smoking levels were investigated by using the multiple regression analysis. RESULTS: SDRs for gender, age and regional differences were significant for 14, 8 and 2 analytes, respectively. BMI-related changes in test results were noted conspicuously for CRP. For some metabolic related parameters the ranges of RIs by non-parametric method were wider than by the parametric method and RIs derived using the LAVE method were significantly different than those without it. RIs were derived with and without gender partition (BMI, drugs and supplements were considered). CONCLUSIONS: RIs applicable to Saudis were established for the majority of chemistry analytes, whereas gender, regional and age RI partitioning was required for some analytes. The elevated upper limits of metabolic analytes reflects the existence of high prevalence of metabolic syndrome in Saudi population.

Assessment of Becton Dickinson Plain and Serum Separator Tubes in Measurement of 25-Hydroxyvitamin D3 (25OHD3) by HPLC and Immunoassay Methods.

BACKGROUND: The accuracy of 25-hydroxyvitamin D3 (25OHD3) measurement on specimens collected into serum separator tubes (SSTs) has been questioned because of possible interference by the gel. Possible interference was investigated in SSTs from Becton Dickinson (BD). DESIGN AND METHODS: Blood specimens were collected simultaneously from 50 normal subjects into plain tubes and SSTs. 25OHD3 was assayed on serum using high performance liquid chromatography (Chromsystems), and Architect (Abbott) and Liaison (Diasorin) immunoassays. RESULTS: There were no significant differences between 25OHD3 results (means ± SE, nmol/l) obtained from specimens collected into plain tubes and SSTs assayed by HPLC (39.0 ± 2.7 vs. 39.3 ± 2.7), Liaison (32.9 ± 2.2 vs. 32.8 ± 2.3), or Architect (43.1 ± 2.8 vs. 43.2 ± 2.8). In specimens collected into plain tubes and SSTs, 25OHD3 measurements by HPLC correlated significantly (P < 0.0001) with those from the Architect (r = 0.895, r = 0.908) and Liaison (r = 0.907, r = 0.913), respectively. CONCLUSIONS: The gel in SSTs (BD) does not interfere with the measurement of 25OHD3 by HPLC or common immunoassays. This important finding may enable clinical laboratories to make cost savings by using SSTs without concerns about inaccuracy.