Utility of Circulating Cell-Free DNA in Assessing Microsatellite Instability and Loss of Heterozygosity in Breast Cancer Using Human Identification Approach.

The diagnostic and prognostic utility of circulating cell-free DNA (cfDNA) in breast cancer (BC) patients was recently reported. Here, we investigated the use of cfDNA to examine microsatellite instability (MSI) and loss of heterozygosity (LOH) for early BC diagnosis. cfDNA and genomic DNA from 41 female BC patients and 40 healthy controls were quantified using NanoDrop spectrophotometry and real-time PCR. The stability of genomic and cfDNA was assessed using a high-resolution AmpFlSTR MiniFiler human identification kit. Significant increases in cfDNA plasma concentrations were observed in BC patients compared to controls. The genotype distribution of the eight autosomal short tandem repeat (STR) loci D7S820, D13S317, D21S11, D2S1338, D18S51, D16S539, FGA, and CSF1PO were in Hardy-Weinberg equilibrium. Significant differences in the allele frequencies of D7S820 allele-8, D21S11 allele-29, allele-30.2, allele-32.2, and CSF1PO allele-11 were seen between BC patients and controls. LOH and MSI were detected in 36.6% of the cfDNA of patients compared to genomic DNA. This study highlights the utility of plasma-derived cfDNA for earlier, less invasive, and cost-effective cancer diagnosis and molecular stratification. It also highlights the potential value of cfDNA in molecular profiling and biomarkers discovery in precision and forensic medicine.

Validation of predictive equations for glomerular filtration rate in the Saudi population.

Predictive equations provide a rapid method of assessing glomerular filtration rate (GFR). To compare the various predictive equations for the measurement of this parameter in the Saudi population, we measured GFR by the Modification of Diet in Renal Disease (MDRD) and Cockcroft-Gault formulas, cystatin C, reciprocal of cystatin C, creatinine clearance, reciprocal of creatinine, and inulin clearance in 32 Saudi subjects with different stages of renal disease. We compared GFR measured by inulin clearance and the estimated GFR by the equations. The study included 19 males (59.4%) and 13 (40.6%) females with a mean age of 42.3 +/- 15.2 years and weight of 68.6 +/- 17.7 kg. The mean serum creatinine was 199 +/- 161 micromol/L. The GFR measured by inulin clearance was 50.9 +/- 33.5 mL/min, and the estimated by Cockcroft-Gault and by MDRD equations was 56.3 +/- 33.3 and 52.8 +/- 32.0 mL/min, respectively. The GFR estimated by MDRD revealed the strongest correlation with the measured inulin clearance (r= 0.976, P= 0.0000) followed by the GFR estimated by Cockcroft-Gault, serum cystatin C, and serum creatinine (r= 0.953, P= 0.0000) (r= 0.787, P= 0.0001) (r= -0.678, P= 0.001), respectively. The reciprocal of cystatin C and serum creatinine revealed a correlation coefficient of 0.826 and 0.93, respectively. Cockroft-Gault formula overestimated the GFR by 5.40 +/- 10.3 mL/min in comparison to the MDRD formula, which exhibited the best correlation with inulin clearance in different genders, age groups, body mass index, renal transplant recipients, chronic kidney disease stages when compared to other GFR predictive equations.

Serum cystatin C: a surrogate marker for the characteristics of peritoneal membrane in dialysis patients.

To evaluate whether cystatin C levels can be a surrogate marker of creatinine clearance and reflect the characteristics of peritoneal membrane in dialysis patients, we performed peritoneal equilibration tests (PET) in 18 anuric adult chronic peritoneal dialysis (PD) patients with a mean age of 39.7 +/- 20 years. All the samples were analyzed for urea, creatinine, and cystatin C. Peritoneal transport, mass transfer, and peritoneal clearance of cystatin C were calculated. Correlation and regression analysis was done using cystatin C as a dependent variable and age, sex, height, weight, body surface area, and creatinine as independent variables. Cystatin C demonstrated a significant time dependent increase of dialysate concentration and decline in the serum concentrations during PET, and a strong correlation between serum creatinine and serum cystatin C concentrations(r: 0.62, p= 0.008). The trans-peritoneal clearance (mL/min/1.73 m 2 ) of cystatin C was related to its serum concentration and was similar to creatinine in its pattern but of smaller magnitude. Peritoneal mass transfer (mg/4 hr per 1.73 m 2 ) for cystatin C serum creatinine was 1.68 +/- 0.67 and 73.3 +/- 29.8, respectively. The dialysis/plasma D/P cystatin C concentration was > or = 0.1 at 4 hrs of PET denoted high peritoneal transport, while the values of < 0.1 denoted low transport type. We conclude that cystatin C follows the same pattern of peritoneal exchange as creatinine but the magnitude of transfer is many folds lower than creatinine. At present clinical utility of cystatin C in the evaluation of solute clearance is probably limited due to the minute amounts transferred across the membrane and the high renal clearance in the presence of residual renal function.

Normal reference levels of serum cystatin C in Saudi adults.

This is the first report from Saudi Arabia studying the normal reference intervals in adult Saudi subjects and evaluating serum cystatin C as a prospective marker for the assessment of the glomerular filtration rate (GFR). Three hundred healthy adult Saudi subjects including 156 males (52%) and 144 females (48%), with a mean age of 31.21 +/- 9.82 years were prospectively studied to establish normal reference ranges for cystatin C. A total of 68.34% of the study patients were in the age-group of 21-40 years. The mean serum cystatin C in the 300 healthy subjects was 0.751 +/- 0.11 mg/L (0.50 - 1.09), increasing gradually with age: it was 0.738 +/- 0.11 mg/L (0.51 - 1.09) in the age-group 21 - 30 years and 0.807 +/- 0.12 (0.51 - 1.09) among subjects who were > 50 years of age. The mean serum cystatin C in females (0.778 +/- 0.118 mg/L) was significantly hig-her than in males (0.726 +/- 0.095 mg/L) (p < 0.0001). The serum cystatin C level was within the defined reference range of 0.53 - 0.95 mg/L in 95% of the subjects with a mean value of 0.74 +/- 0.097 mg/L, and was falling within the 95% confidence interval of 0.73865 - 0.7637 mg/L, and with 98.84% area under the curve (AUC). All the other renal function markers (urea, serum creatinine, calculated GFR, BMI) among the studied subjects were within the normal reference ranges for adult Saudi population. The serum cystatin C level had a significant correlation with the body mass index (BMI) (r = 0.155; p = 0.007) and a correlation with serum creatinine as well (r = 0.009; p = 0.873). It showed a negative correlation with calculated GFR as per Cockroft-Gault equation (r = - 0.101; p = 0.083).