Estimated Glomerular Filtration Rate (eGFR): A Serum Creatinine-Based Test for the Detection of Chronic Kidney Disease and its Impact on Clinical Practice

Abstract Chronic kidney disease (CKD) is an important epidemic and public health problem that is associated with a significant risk for vascular disease and early cardiovascular mortality as well as progression of kidney disease. Currently it is classified into five stages based on the glomerular filtration rate (GFR) as recommended by many professional guidelines. Radiolabelled methods for measuring GFR are accurate but not practical and can be used only on a very limited scale while the traditional methods require timed urine collection with its drawback of inaccuracy, cumbersomeness and inconvenience for the patients. However, the development of formula-based calculation of estimated GFR (eGFR) has offered a very practical and easy approach for converting serum creatinine value into GFR result taking into consideration patient's age, sex, ethnicity and weight (depending on equation type). The commonly used equations include Cockraft and Gault (1976), Modification of Diet in Renal Disease (MDRD) (1999) and Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) (2009). It is the implementation of these equations particularly the MDRD that has raised the medical awareness in the diagnosis and management of CKD and its adoption by many guidelines in North America and Europe. The impact and pitfalls of each of these equations in the screening, diagnosis and management of patients with CKD are presented and discussed in this review

Reference Ranges of Serum Anti-Müllerian Hormone in Healthy Reproductive-aged Omani Women

Objectives: Anti-Müllerian hormone (AMH), a glycoprotein that belongs to the transforming growth factor-beta superfamily, is important for women’s health. We aimed to determine the age-specific reference range of serum AMH in healthy Omani women from reproductive ages to menopause. Methods: This cross-sectional cohort study was conducted among a group of healthy 20–50 years old Omani women. The participants were required to have body mass index < 32 kg/m2 regular periods, no history of chronic illness, polycystic ovary syndrome, or gynecological operation. They were also required to not be using any hormonal contraceptive. Serum concentrations of AMH, follicle-stimulating hormone, luteinizing hormone, progesterone, and hemoglobin A1c were measured. AMH-age nomogram and AMH levels were compared between the six selected age groups. Results: The subjects were 319 Omani women aged 20–50 years. Serum AMH concentrations were found to decrease progressively with increasing age. An exponential model defined as √AMH = 479.02 × 0.91age was selected to explain the reduction in AMH with age (R2 = 0.298). The median AMH levels were 26.61 pmol/L for those aged 20–25 years, 20.89 pmol/L for 26–30 years, 19.92 pmol/L for 31–35 years, 13.71 pmol/L for 36–40 years, 9.24 pmol/L for 41–45 years, and 0.68 pmol/L for 46–50 years. The recommended 2.5thto 97.5thpercentiles of AMH level, as reference ranges for various age groups, were found to be: 10.63–55.64 pmol/L (20–25 years), 3.74–61.88 pmol/L (26–30 years), 5.49–47.56 pmol/L (31–35 years), 2.15–48.91 pmol/L (36–40 years), 0.92–41.26 pmol/L (41–45 years), and 0.14–5.10 pmol/L (46–50 years).Conclusions: This study (the first in Oman) determined the age-specific reference ranges of serum AMH in healthy Omani women in the age range of 20–50 years

Are Tubes Containing Sodium Fluoride Still Needed for the Measurement of Blood Glucose in Hospital Laboratory Practice?

Objectives: To compare glucose values obtained using sodium flouride (NaF) tubes and serum separation tubes (SST) in a tertiary care hospital laboratory setting.  Methods: This study was conducted at the Clinical Biochemistry Laboratory, Royal Hospital, Oman. During the study period (1 September–30 November 2013), 50 pairs (one NaF tube and one SST) of patient’s blood specimens were randomly collected. Following separation of plasma (NaF tubes) and serum (SST), glucose concentrations were measured by hexokinase assay using the Architect c8000. Fifteen pairs of these tubes were kept in the refrigerator at 4°C and plasma/serum glucose concentrations were measured daily up to seven days after collection.  Results: Comparing plasma (NaF) and serum (SST) results of glucose values (n=50) showed an average difference of 0.00mmol/L (range -0.60 to +0.60mmol/L). Bland Altman analysis gave a non-significant constant bias of 0.10 ±0.195mmol/L (bias ±SD). Pearson correlation between plasma (NaF) and serum (SST) glucose concentrations revealed a significant correlation approaching unity with r2= 0.9991. No significant differences in glucose values were noted for both plasma and serum in 15 pairs of NaF and SST tubes when analyzed seven days following refrigeration. Hemolysis was observed in five (10%) NaF tubes compared with two (4%) SST.  Conclusion: There is no difference in glucose values collected from plasma NaF tubes or serum SST, and so SST can be used in hospital laboratory settings as there are practical advantages, including cost-effectiveness and reduction in blood volume drawn when utilizing these tubes for glucose and other tests from a single blood collection tube

Comparison between Three Different Equations for the Estimation of Glomerular Filtration Rate in Omani Patients with Type 2 Diabetes Mellitus

Objectives: Estimated glomerular filtration rate (eGFR) is an important component of a patient’s renal function profile. The Modification of Diet in Renal Disease (MDRD) equation and the Chronic Kidney Disease-Epidemiology Collaboration (CKD-EPI) equation are both commonly used. The aim of this study was to compare the performance of the original MDRD186, revised MDRD175 and CKD-EPI equations in calculating eGFR in type 2 diabetes mellitus (T2DM) patients in Oman. Methods: The study included 607 T2DM patients (275 males and 332 females, mean age ± standard deviation 56 ± 12 years) who visited primary health centres in Muscat, Oman, during 2011 and whose renal function was assessed based on serum creatinine measurements. The eGFR was calculated using the three equations and the patients were classified based on chronic kidney disease (CKD) stages according to the National Kidney Foundation Kidney Disease Outcomes Quality Initiative guidelines. A performance comparison was undertaken using the weighted kappa test. Results: The median eGFR (mL/min/1.73 m2) was 92.9 for MDRD186, 87.4 for MDRD175 and 93.7 for CKD-EPI. The prevalence of CKD stage 1 was 55.4%, 44.7% and 57% while for stages 2 and 3 it was 43.2%, 54% and 41.8%, based on MDRD186, MDRD175 and CKD-EPI, respectively. The agreement between MDRD186 and CKD-EPI (к 0.868) was stronger than MDRD186 and MDRD175 (к 0.753) and MDRD175 and CKD-EPI (к 0.730). Conclusion: The performances of MDRD186 and CKD-EPI were comparable. Considering that CKD-EPI-based eGFR is known to be close to isotopically measured GFR, the use of MDRD186 rather than MDRD175 may be recommended

Estimated Glomerular Filtration Rate (eGFR): A Serum Creatinine-Based Test for the Detection of Chronic Kidney Disease and its Impact on Clinical Practice

Chronic kidney disease (CKD) is an important epidemic and public health problem that is associated with a significant risk for vascular disease and early cardiovascular mortality as well as progression of kidney disease. Currently it is classified into five stages based on the glomerular filtration rate (GFR) as recommended by many professional guidelines. Radiolabelled methods for measuring GFR are accurate but not practical and can be used only on a very limited scale while the traditional methods require timed urine collection with its drawback of inaccuracy, cumbersomeness and inconvenience for the patients. However, the development of formula- based calculation of estimated GFR (eGFR) has offered a very practical and easy approach for converting serum creatinine value into GFR result taking into consideration patient’s age, sex, ethnicity and weight (depending on equation type). The commonly used equations include Cockraft and Gault (1976), Modification of Diet in Renal Disease (MDRD) (1999) and Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) (2009). It is the implementation of these equations particularly the MDRD that has raised the medical awareness in the diagnosis and management of CKD and its adoption by many guidelines in North America and Europe. The impact and pitfalls of each of these equations in the screening, diagnosis and management of patients with CKD are presented and discussed in this review

Serum Myoglobin in Patients with Thyroid Dysfunction

Objectives: To assess the pattern of change in serum myoglobin concentration in subjects with thyroid dysfunction. Methods: Serum samples were selected from 150 subjects with suspected thyroid disorder who were referred to the Royal Hospital, Muscat, Oman. The subjects were 35 males and 115 females, aged 14-56 years with mean ± SD of 34.3 ± 12.7 years. They were classified on the basis of thyroid stimulating hormone (TSH) and free thyroxine (FT4) into 3 groups, each consisting of 50 subjects: hypothyroid, hyperthyroid, and euthyroid subjects. Results: The mean serum myoglobin concentration was higher in hypothyroid patients compared to hyperthyroid and euthyroid subjects (mean ± SD was 38.5 ± 23.1 µg/L in hypothyroid; 18.1 ± 7.0µg/L in hyperthyroid; 17.4 ± 5.7µg/L in euthyroid). There was a significant difference in myoglobin concentration between hypothyroid and euthyroid groups (F = 36.1, p&lt; 0.001), however, there was no significant difference between the hyperthyroid and euthyroid groups. When the mean ± 2SD for myoglobin in euthyroid subjects was calculated, the reference range was 6-29 µg/L. Of the hypothyroid subjects, 29 (58%) had high myoglobin and 21 (42%) had normal myoglobin level. No significant correlation was noticed between TSH or FT4 and myoglobin in all studied subjects. Conclusion:Raised serum myoglobin may be observed in patients with hypothyroidism. Hence hypothyroidism should be considered in the differential diagnosis of patients with raised serum myoglobin concentration