Lena Jafri

Comparison of high performance liquid chromatography, radio immunoassay and electrochemiluminescence immunoassay for quantification of serum 25 hydroxy vitamin D

OBJECTIVE To compare the performance of radioimmunoassay (RIA) with high-performance liquid chromatography (HPLC) and electrochemiluminescence (ECLIA) for the quantification of vitamin D (25OHD). METHODS HPLC method for the determination of 25OHD in human biological samples was developed and compared in terms of accuracy and precision with a commercially available RIA assay. Performance of RIA assay with ECLIA technology for 25OHD analysis was further compared. RESULTS Median 25OHD levels with HPLC vs. RIA were 50.1nmol/L (IQ=17.7-199.4nmol/L) and 51.1nmol/L (IQ=12.5-187.2nmol/L) respectively, whereas median 25OHD concentration with RIA vs. ECLIA was 32.4nmol/L (9.98-199.7nmol/L) and 29.9nmol/L (4.9-214.6nmol/L), respectively. Comparison data for HPLC vs. RIA showed RIA=-1.13+1.01 (HPLC) (RMSE=11.2nmol/L) and for RIA vs. ECLIA revealed, ECLIA=3.21+0.9 (RIA) (RMSE9.6nmol/L). CONCLUSION Acceptable correlation was observed among HPLC and RIA and also with RIA and ECLIA in quantification of 25OHD.

B-type natriuretic peptide versus amino terminal pro-B type natriuretic peptide: selecting the optimal heart failure marker in patients with impaired kidney function

BackgroundThe effect of impaired kidney function on B-type natriuretic peptide (BNP) and N-terminal proBNP (NT-proBNP) is vague. This study was performed to examine the effect of kidney dysfunction on the afore-mentioned markers and determine appropriate cutoffs for systolic heart failure (SHF).MethodsIn this cross sectional study adults with estimated glomerular filtration rate (eGFR) <60 ml/min for ≥3 months were identified in consulting clinics from June 2009 to March 2010. SHF was defined as documented by a cardiologist with ejection fraction of < 40% and assessed by New York Heart Association classification (NYHA). Plasma was assayed for creatinine (Cr), BNP and NT-proBNP.ResultsA total of 190 subjects were enrolled in the study, 95 with and 95 without SHF. The mean age of patients was 58 (±15) years, 67.4% being males. Mean BNP levels showed a 2.5 fold and 1.5 fold increase from chronic kidney disease (CKD) stage 3 to stage 5 in patients with and without SHF respectively. NT-proBNP levels in non-heart failure group were 3 fold higher in CKD stage 5 compared to stage 3. Mean NT-proBNP levels were 4 fold higher in CKD stage 5 compared to stage 3 in patients with SHF. Optimal BNP and NT-proBNP cutoffs of SHF diagnosis for the entire CKD group were 300 pg/ml and 4502 pg/ml respectively.ConclusionBNP and NT-proBNP were elevated in kidney dysfunction even in the absence of SHF; however the magnitude of increase in NT-proBNP was greater than that of BNP. BNP and NT-proBNP can be useful in diagnosing SHF, nonetheless, by using higher cutoffs stratified according to kidney dysfunction. NT-proBNP appears to predict heart failure better than BNP.

Error identification in a high-volume clinical chemistry laboratory: Five-year experience

Abstract Introduction. Quality indicators for assessing the performance of a laboratory require a systematic and continuous approach in collecting and analyzing data. The aim of this study was to determine the frequency of errors utilizing the quality indicators in a clinical chemistry laboratory and to convert errors to the Sigma scale. Materials and methods. Five-year quality indicator data of a clinical chemistry laboratory was evaluated to describe the frequency of errors. An ‘error’ was defined as a defect during the entire testing process from the time requisition was raised and phlebotomy was done until the result dispatch. An indicator with a Sigma value of 4 was considered good but a process for which the Sigma value was 5 (i.e. 99.977% error-free) was considered well controlled. Results. In the five-year period, a total of 6,792,020 specimens were received in the laboratory. Among a total of 17,631,834 analyses, 15.5% were from within hospital. Total error rate was 0.45% and of all the quality indicators used in this study the average Sigma level was 5.2. Three indicators – visible hemolysis, failure of proficiency testing and delay in stat tests – were below 5 on the Sigma scale and highlight the need to rigorously monitor these processes. Conclusions. Using Six Sigma metrics quality in a clinical laboratory can be monitored more effectively and it can set benchmarks for improving efficiency.

Fourier transform infrared spectroscopy for analysis of kidney stones

Purpose To compare the results of a chemical method of kidney stone analysis with the results of Fourier transform infrared (FT-IR) spectroscopy. Materials and Methods Kidney stones collected between June and October 2015 were simultaneously analyzed by chemical and FT-IR methods. Results Kidney stones (n=449) were collected from patients from 1 to 81 years old. Most stones were from adults, with only 11.5% from children (aged 3–16 years) and 1.5% from children aged <2 years. The male to female ratio was 4.6. In adults, the calcium oxalate stone type, calcium oxalate monohydrate (COM, n=224), was the most common crystal, followed by uric acid and calcium oxalate dihydrate (COD, n=83). In children, the most frequently occurring type was predominantly COD (n=21), followed by COM (n=11), ammonium urate (n=10), carbonate apatite (n=6), uric acid (n=4), and cystine (n=1). Core composition in 22 stones showed ammonium urate (n=2), COM (n=2), and carbonate apatite (n=1) in five stones, while uric acid crystals were detected (n=13) by FT-IR. While chemical analysis identified 3 stones as uric acid and the rest as calcium oxalate only. Agreement between the two methods was moderate, with a kappa statistic of 0.57 (95% confidence interval, 0.5–0.64). Disagreement was noted in the analysis of 77 stones. Conclusions FT-IR analysis of kidney stones can overcome many limitations associated with chemical analysis.

Osteoporosis and its perspective in Pakistan: A review of evidence and issues for addressing fragility fractures

Despite major advances in osteoporosis diagnosis and treatment, low rates of investigating and treating osteoporosis in patients with fragility fracture are reported in Pakistan. Cost of therapies, time and cost of resources for diagnosis, concerns about medications and lack of clarity regarding the onus of responsibility to undertake this care, are some of the barriers to osteoporosis identification and treatment. Data from our part of the world on osteoporosis as well as on fragility fractures is sparse. This review addresses the current screening and diagnostic strategies for osteoporosis and reviews the existing literature to highlight the issues prevalent in our society on this major public health problem.

Primary hyperoxaluria in populations of Pakistan origin: results from a literature review and two major registries

Primary hyperoxalurias (PH) are devastating, autosomal recessive diseases causing renal stones. Undifferentiated hyperoxaluria is seen in up to 43% of Pakistani paediatric stone patients. High rates of consanguinity in Pakistan suggest significant local prevalence. There is no detailed information regarding number of cases, clinical features, and genetics in Pakistan-origin (P-o) patients. We reviewed available information on P-o PH patients recorded in the literature as well as from two major PH registries (the Rare Kidney Stone Consortium PH Registry (RKSCPHR) and the OxalEurope PH Registry (OxER); and the Aga Khan University Hospital in Pakistan. After excluding overlaps, we noted 217 P-o PH subjects (42 in OxER and 4 in RKSCPHR). Presentations were protean. Details of mutations were available for 94 patients of 201 who had genetic analyses. Unique mutations were noted. Mutation [c.508G>A (p. Gly170Arg)] (present in up to 25% in the West) was reported in only one case. In one series, only 30% had mutations on exons 1,4,7 of AGXT. Of 42 P-o patients in OxER, 52.4% were PH1, 45.2% PH2, and 2.4% PH3. Of concern is that diagnosis was made after renal transplant rejection (four cases) and on bone-marrow aspiration (in five). Lack of consideration of PH as a diagnosis, late diagnosis, and loss of transplanted kidneys mandates that PH be searched for diligently. Mutation analysis will need to extend to all exons and include PH 1,2,3. There is a need to spread awareness and identify patients through a scoring or screening system that alerts physicians to consider a diagnosis of PH.

Prospective evaluation of serum procalcitonin in critically ill patients with suspected sepsis- experience from a tertiary care hospital in Pakistan

Background Sepsis is the leading cause of mortality in critically ill patients. Procalcitonin (PCT) is a promising marker for identification of bacterial sepsis. The aim of this study was to determine the diagnostic accuracy of serum PCT concentration in patients with suspected sepsis admitted to mixed medical-surgical Intensive care unit (ICU). Material and methods A cross-sectional study conducted at section of Chemical Pathology, Department of Pathology and Laboratory Medicine and ICU. Patients with suspected sepsis were included, serum PCT cut off ≥0.5 ng/ml was taken for diagnosing sepsis. Diagnostic accuracy was measured in terms of sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) taking blood culture as gold standard. Furthermore, different cut offs were compared by using receiver operating characteristic curves (ROC). Data analysis was done on SPSS version 20. Results Median age of the study group (n = 103) was 48 years (IQR: 22), 60% being males. Out of the 103 patients included 82 patients had PCT levels above the optimal cut off. At a serum PCT cutoff of 0.5 μg/L, the sensitivity and specificity for the diagnosis of sepsis was found to be 93.75% and 43.59% respectively. NPV was higher compared to PPV making PCT a reliable marker to for the screening out of sepsis patients. Furthermore, it was revealed that PCT having an AUC = 0.70 outperformed WBC (AUC = 0.5) and CRP (AUC = 0.6). Conclusion Elevated PCT concentration is a promising indicator of sepsis in newly admitted critically ill patients capable of complementing clinical signs and routine laboratory parameters.

Automated Reporting of Estimated Glomerular Filtration Rate: A Comparison of Creatinine Clearance, Modification of Diet in Renal Disease and Cockcroft Gault Equations from Pakistan

Objectives: To facilitate early detection of chronic kidney disease, many organizations now recommend reflex reporting of estimated glomerular filtration rate (eGFR) whenever serum creatinine (Cr) is measured. To compare two widespread eGFR equations with creatinine clearance (CrCl) calculated through a timed urine collection. Methodology: Laboratory data of subjects’ ≥ 18 years tested for CrCl from October 2010 to December 2010 was retrieved from laboratory information system of Aga Khan University Hospital. Statistical comparison of eGFR using Cockcroft Gault (CG) and 4variable Modification of Diet in Renal Disease (MDRD) formulae with CrCl was performed. Results: Six hundred and seventy subjects with CrCl were studied. Mean age of the group was 51 ±15 years, 55.7 % being males. Mean glomerular filtration rate using CrCl, MDRD and CG were 57.1 (±35.9), 57.8 (±33.6) and 68.7 (±41.5) ml/min respectively. Deming regression analysis generated MDRD = 5.23 + 0.92 (CrCl) and CG = 0.23 + 1.2 (CrCl) for comparison of CrCl results with those of MDRD and CG respectively. Comparing MDRD and CrCl, Bland Altman revealed acceptable agreement with a minimal bias of 0.65 ml/min.