A. S. Kanagasabapathy

Rate of Progression of Albuminuria in Type II Diabetes: Five-year prospective study from South India

OBJECTIVE To evaluate the potential risk factors for the progression of albuminuria in type II diabetes. RESEARCH DESIGN AND METHODS A cohort of 481 type II diabetic patients were followed prospectively for 5 years. Blood glucose (BG) and blood pressure (BP) were checkedat 2 monthly intervals, and urinary albumin excretion (UAE) was checked at yearly intervals. Progression of albuminuria was recognized by the development of microalbuminuria and macroalbuminuria and a significant increase in albuminuria within the microalbuminuric range. RESULTS UAE was normal in 349 patients, 93 patients were microalbuminuric, and the rest (39) were macroalbuminuric. Sixty-two patients with normal UAE developed microalbuminuria. Ten patients with normoalbuminuria and 23 with microalbuminuria developed macroalbuminuria during the 5-year observation period with overall incidence of 46.9/1,000 person-years for normoalbuminuria and 58.7/1,000 person-years for microalbuminuria. Baseline UAE was significantly higher in those patients who progressed compared with those patients who did not (normoalbuminuria: 8.5 ± 6 vs. 5.3 ± 4 μg/min, P < 0.001; microalbuminuria: 68.5 ± 57 vs. 47.4 ± 34 μg/min, P < 0.01). Multiple regression analysis revealed initial UAE and diabetes durationto be predictors of albuminuria progression. CONCLUSIONS Initial UAE is a strong predictor of albuminuria progression intype II diabetic patients.

Urinary N-acetyl-β-d-glucosaminidase and aminopeptidase N in the diagnosis of graft rejection after live donor renal transplantation

An evaluation of the usefulness of urinary N-acetyl-beta-D-glucosaminidase (NAG) and aminopeptidase N (AAP) measurements in the diagnosis and prediction of acute and chronic renal allograft rejection was made. Enzyme activities were measured in 2,745 morning spot urine samples from 53 consecutive live donor renal allograft recipients up to 180 days after transplantation. Reference ranges of urinary enzyme activities in 14 recipients with normal graft function were higher than those established in a carefully selected group of healthy controls. 89 and 91% of 76 clinically diagnosed acute rejection episodes (ARE) in the remaining 39 graft recipients were accompanied by sharp increase over baseline of NAG and AAP respectively. All rejection episodes occurring in the early period after transplantation were characterised by high enzymuria. AAP was more sensitive than NAG as the magnitude of its increase over baseline was more, while NAG was more specific with less number of false positive elevations. Both enzymes were found to be equally good prognostic indices of graft loss and chronic graft deterioration. Regular monitoring of urinary NAG and AAP activities throughout the post transplant period would thus be valuable in (a) diagnosis and prediction of ARE in the early as well as late post operative period and (b) prediction of eventual graft outcome.

Urinary protein/creatinine ratio as an indicator of allograft function following live related donor renal transplantation.

In a study of 656 urine specimens from 53 consecutive recipients of live related donor renal allografts we found an excellent correlation between the protein content of 24-h urines and protein/creatinine ratio (Up/Ucr) in overnight urine samples. Using this ratio, we evaluated proteinuria up to 180 days after renal transplantation (overnight urine samples analysed, n = 2745). Heavy proteinuria in the immediate post-operative period had no prognostic significance. Eighty-nine percent of all clinically observed acute rejection episodes were accompanied by an increase over baseline of Up/Ucr; in 56.5% of these episodes elevation of Up/Ucr preceded that of serum creatinine. However, as a marker of rejection the usefulness of this parameter was limited owing to large number of false positive elevations. In 50 recipients whose grafts survived for more than 3 mth, proteinuria was graded into minimal, moderate and heavy. Renal function at the end of six months was good in all patients who exhibited proteinuria with Up/Ucr less than 100 mg/mmol creatinine. Persistent proteinuria with Up/Ucr above 100 mg/mmol preceded significant deterioration of graft function. Therefore, a protein-creatinine ratio of 100 mg/mmol can be considered as an apparent cut-off to differentiate stable from deteriorating graft function in long term evaluation of transplant recipients.

Fractionation of cystine aminopeptidases (‘oxytocinase’) from term human placenta and maternal serum

Cystine aminopeptidase (EC 3.4.11.3) enzymes, present in term human placenta and maternal serum, were compared with respect to their behaviour on ion-exchange columns, Km and pH optima, chelator, metal ion and L-methionine effects, Sepharose 6B elution profiles and molecular weights. From placental extracts two activity peaks (CAS I and II) hydrolysing S-benzyl L-cysteine paranitroanilide were separated on DEAE Sephacel. Differences in properties between the two forms were evident. Maternal serum enzyme eluted from the DEAE Sephacel column in a position similar to that of placental CAS I. In addition, the maternal serum enzyme was similar in properties to placental CAS I. It is possible that of all the different cystyl aminopeptidase enzyme systems present in placental tissue, only one appears in maternal blood.

Urinary N‐Acetyl‐β‐D‐Glucosaminidase in the Prediction of Preeclampsia and Pregnancy‐induced Hypertension

Summary: Urinary N‐acetyl‐ β‐D‐glucosaminidase was estimated in 109 primigravidas and the level correlated with the subsequent development of preeclampsia and pregnancy‐induced hypertension in these women. The enzyme value was significantly higher in those who developed preeclampsia. Its sensitivity and specificity for the prediction of the disorder were 80% and 78% respectively. The positive predictive value was 21% while the negative predictive value was 98%.

Quality control in clinical biochemistry

ConclusionThis paper describes QC techniques towards day-to-day monitoring of the reliability of Clinical Biochemistry laboratory performance. Application of these techniques will help reduce errors and give both the laboratory and the clinician confidence in the results. Through the sustained efforts of the ACBI, it will be certainly possible to encourage all Indian laboratories to implement QC as an integral part of laboratory practice.

Cystyl Aminopeptidase in Maternal Serum for the Antenatal Recognition of Fetal Growth Retardation

An appraisal has been made of the usefulness of cystyl aminopeptidase (CAS, E.C. 3.4.11.3) activity patterns in the in utero detection of fetal growth retardation; 196 pregnancies at risk from placental insufficiency, classified into 9 aetiologic groups were considered. Absolute levels and trend of enzyme activity were studied in all cases and compared with the reference range of CAS activity established in 267 healthy pregnant subjects. Excluding multiple pregnancies, overall predictive value of CAS in defining fetal outcome in 186 ‘at risk’ pregnancies was 72%, overall sensitivity and specificity being 82% and 71% respectively; 48% of the ‘at risk’ population delivered growth retarded infants, whereas the prevalence of growth retardation as diagnosed by CAS was 54%. Out of the 89 patients who delivered growth retarded infants, 73 exhibited abnormal CAS activity patterns. In twin pregnancies, values of CAS in 73% of the total number of assays were above mean plus 2 standard deviations for the respective gestational period. CAS in maternal serum is advocated as a simple and reliable antepartum indicator of fetal growth retardation and is suitable for the detection of twin pregnancy as early as the second trimester.

Effective laboratory quality management towards preventing medical liability cases.

The last decade has seen a rapid expansion of the various branches of health care services in India. This has seen a corresponding increase in consumer knowledge, which has resulted in (a) increased demand for high quality services and (b) these services to be provided in a timely manner. Medical laboratory plays a central role in the delivery of these services as over 70% of clinical decisions are taken based on laboratory reports (1). An important component in the whole process is laboratory error and an expectation to get error free services. With growing awareness amongst customers, in this case largely patients, and increasing cost, medico- legal litigations are on the rise. Court cases are often filed against doctors by patients for real or perceived reasons of dissatisfaction. Medical malpractice law suits against medical laboratories are also on the rise. This has placed a significant onus and urgency on clinical laboratories to ensure that quality and error free work practices are maintained. There has been a steady improvement in the quality of tests due to improved technology. Laboratory automation has also taken on a new level of importance in improving quality. We have the ability now to get instruments interfaced to various laboratory information systems. Information technology has consequently taken a giant leap in the field of biomedical equipment to drastically reduce manual intervention during the analytical procedure without compromising on established levels of care.

N-acetyl-β-D-glucosaminidase, alanine aminopeptidase and protein: Creatinine ratio as early indicators of diabetic microangiopathy

The urinary excretion patterns of N-acetyl-β-D-glucosaminidase (NAG), alanine aminopeptidase (AAP) and protein/creatinine ratio (UP/UCR) were studied in 133 diabetic subjects under treatment, 7 patients with established diabetic nephropathy (DN) and 79 carefully selected (age-matched) healthy subjects. NAG, AAP and UP/UCR were highly elevated in DN, while in diabetics urinary NAG levels correlated well with the degree of long-term metabolic control indicated by glycosylated hemoglobin (GHB or Hba1). Both AAP and UP/UCR were found to be more sensitive than NAG, but less specific. Urinary NAG and AAP assays thus offer simple, sensitive and non-invasive techniques for prognostic indication of the onset of microangiopathic changes in long-term diabetic subjects.

Study of some factors affecting stability of N-acetyl-β-D-glucosaminidase and aminopeptidase N in urine at 37°C

Little is known of conditions which influence the stability of urinary enzymes upon storage in the bladder at 37°C. Using a continuous flow system simulatingin vivo conditions, we studied the influence of the pH of urine on the stability of two renal parenchymal enzymes N—Acetyl—β—D—Glucosaminidase (2—acetamido—2—deoxy—β—D—glucoside acetamidodeoxy glucohydrolase, NAG, EC 3.2.1.30) and L—Alanine aminopeptidase (Aminopeptidase N, AAP, EC 3.4.11.2). This continuous flow model that we have described can be employed to study the influence of pH on the stability of any renal enzyme excreted in urine. We also studied thein vitro effects of varying concentrations of low molecular weight regulatory metabolites such as urea, creatinine and uric acid and of some drugs excreted in urine, on the assay of these two enzymes. Urinary pH, urea content and some antibiotics seem to influence measured urinary NAG and AAP activities and we therefore express the need for caution before diagnostic interpretation of the urinary enzyme activities are made.