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DETERMINATION OF GLYCOSYLATED HEMOGLOBIN REFERENCE RANGE IN ADULT POPULATION ATTENDING A MILITARY CARE SET UP IN RAWALPINDI.

Byline: Syed Khawar Ali (Late), Dilshad Ahmed Khan and Farooq Ahmed Khan

Abstract

Objective: To determine the glycosylated hemoglobin reference range in healthy adult population attending a military care setup in Rawalpindi in accordance with National Glycohemoglobin Standardization Program (NGSP) and International Federation of Clinical Chemistry (IFCC)

Study Design: Descriptive cross-sectional study

Place and Duration of Study: Armed Forces Institute of Pathology Rawalpindi from May - Oct 2010

Subjects and Methods: A total of 254 healthy adults (18-80 years) comprising 169 males and 85 females, were included by non probability consecutive sampling from Rawalpindi. History and clinical examination were carried out. Blood HbA1c was analyzed high performance liquid chromatography on biorad D-10. Data were analyzed by SPSS-17.

Results: Total 254 subjects consisting of 169 males and 85 females were recruited from Rawalpindi Pakistan. The reference range of total population was found 4.6-6.56% and 2.69-4.81 mmol/mol in accordance with NGSP and IFCC, respectively. When compared in gender, HbA1c levels were not significantly changed. However, the healthy elderly population had higher HbA1c levels. Reference range for HbA1c based on NGSP in individuals less than 40 years was found 4.52-6.4% while for individuals aged greater than 40 years, it was 4.8-6.68%..

Conclusion: The reference ranges for healthy individuals and the recommended values for optimal therapy in diabetic patients have to be revised and adjusted. Population based reference ranges should be established to provide better patient care services.

Article

INTRODUCTION

The glycosylated hemoglobin (HbA1c) assay has become the gold-standard for monitoring of glycemic control in diabetes mellitus over two decades1. Plasma glucose level is directly associated with HbA1c2. It is easy to interpret, cost effective and routinely used to monitor long-term glycemic control3 as it is directly related to the risks for diabetic complications4. By performing HbA1c test, patient's average glycemic control over the preceding 2-3 months can be measured3. The relationship between HbA1c and estimated average glucose has been established recently5. HbA1c has less intra-individual variation and more reproducibility than fasting plasma glucose and oral glucose tolerance test (OGTT)6. Studies showed the value of 2 standard deviation (SD) above the normal mean is significant in identifying high proportion of undiagnosed diabetic individuals6. This advocates use of HbA1c as an important screening and diagnostic test for diabetes mellitus7. National Glycohemoglobin Standardization Program (NGSP) and

International Federation of Clinical Chemistry (IFCC) have standardized HbA1c assays8. It is suggested that HbA1c should be reported in both NGSP (%) and IFCC (mmol/mol) units9.

HbA1 c levels variation based on gender, age and ethnic groups in healthy population have been reported 10-12. In Thai healthy individuals, reference range of HbA1c were found 4.79% -6.15%11. In a study conducted in USA , mean HbA1c levels were varied among different ethnic populations; 4.93% (+ 0.04) in non-Hispanic whites and 5.05% (+ 0.02) in Mexican-Americans to 5.17% ( +0.02) in non-Hispanic blacks 12. In another study conducted in Kuwaiti population, the mean HbA1c level was 4.8% with a standard deviation of 0.5%13. Thus to use HbA1c as diagnostic tool in a local population, it is also recommended that each laboratory should establish its own reference range of HbA1c for non diabetic individuals8.

We are using the reference range which is based on foreign data and may not represent our non diabetic range. This is the first study to determine HbA1c reference range in Pakistani population. There exists a need of establishing a reference range for HbA1c in our medical set up so that it can be used for diagnosis, screening and monitoring of our diabetic patients.

SUBJECTS AND METHOD

The present study protocol was approved by the Ethics Committee, Armed Forces Institute of Pathology Rawalpindi. It was a descriptive cross-sectional study conducted on a total of 254 healthy subjects at Armed Forces Institute of Pathology, Rawalpindi from May 2010 - Oct 2010. The healthy adults aged between 18 and 80 years comprising of males (n=169) and females (n=85), inhabitants of Rawalpindi , coming for routine annual medical checkup in military health care setup , were selected by non probability consecutive sampling and included in the study. Medical check up of all the subjects was done. Individuals having history of any acute or chronic illness, fasting plasma glucose greater than 5.6 mmol/L, anemia, hemoglobinopathy, pregnancy or individuals taking any medication were excluded from the study. After the informed consent was obtained, whole blood samples were obtained for analysis of HbA1c. HbA1c was determined by high performance liquid chromatography (HPLC) using Biorad D-10.

The results were obtained according to NGSP and afterward NGSP results were converted to IFCC using the master equation 14.

NGSP = (0.915 X IFCC) +2.15. Mathematically, it can also be written as

IFCC = (NGSP - 2.15) / 0.915.

The reference range was evaluated using mean +- 2 SD in accordance with National Committee on Clinical Laboratory Standards (NCCLS) recommendation15

Statistical Analysis

The data were analyzed using SPSS version 17. Descriptive study was used to describe the data. Independent sample t-test was used to compare HbA1c between males and females and between different age groups . The p value less than 0.05 was considered statistically significant. Three levels of controls were analyzed for intra assay coefficient of variation (CV).

RESULTS

Total 254 subjects consisting of 169 (66.5%) males and 85(33.5%) females were recruited . Baseline characteristics of the participants are shown in Table-1.

Table-1: Baseline characteristics of the participants

###Total###Male###Female

###(Mean+-SD)###(Mean+-SD)###(Mean+-SD)

Age (Years)###41.07+-15.6###40.82+-16.###42.74+-15.5

###9###93###1

BMI (kg/m2)###24.67+-0.52###24.6 +-0.56###242+-0.43

Blood Pressure (mm Hg)

Systolic###120.40+-0.8###123.3+-0.81###1205+-0.75

Diastolic###80.1+-0.85###80.1+-3.81###79.9+-0.91

Fasting###4.0+-0.49###4.0+-0.52###3.9+-0.44

plasma

glucose

(mmo1/1)

(mmo1/1)

The healthy volunteers had mean + SD of HbA1c 5.58+-0.49% based on NGSP while according to IFCC, it was 3.75+-0.53. The reference range of total population was found 4.6-6.56% and 2.69-4.81 mmol/mol in accordance with NGSP and IFCC, respectively.

HbA1c levels were not significantly changed in males as compared with females (Table-2).

Table-2: Comparison of HbAlc levels in relation with age and gender

Independent###HbA1c (NGSP%)###HbA1c

variable###Mean +-SD###(IFCC

###mmol/mol)

###Mean+-SD

Age ( years)

less than 40

( n = 143)###5.46+-0.47###3.62+-0.51

greater than

40(n = 111)###5.74+-0.47###3.9+-0.51

p - value###0.001###0.001

Gender

Males (n =169)###5.61+-0.51###3.78+-0.56

Females(n =85)###5.54+-0.43###3.7+-0.47

p - va1ue###0.298###0.298

p value less than 0.05 was considered statistically significant

However, the healthy elderly population had higher HbA1c levels (Table-2). Reference range for HbA1c based on NGSP in individuals less than 40 years was found 4.52 - 6.4 % while for individuals aged greater than 40 years, it was 4.8 - 6.68%. According to IFCC, it was 2.6 - 4.64 mmol/mol and 2.88 - 4.92 mmol/mol for age groups less than 40 years and greater than 40 years old, respectively. The intra-assay total CVs of HbA1c were 2.6%, 1.9% and 1.6% for low, normal and high levels of controls, respectively.

DISCUSSION

This is the first study in Pakistan for the evaluation of reference range for HbA1c and the reference range of HbA1C for total population was found to be 4.6 - 6.56% and of 2.69-4.81 mmol/mol, in accordance with NGSP and IFCC, respectively. The reference range of HbA1c is slightly higher than that of Western12 and Kuwaiti13 population. However, our data was more in coherence with data from Thai11 population. This data support the recommendation of NCCLS to encourage laboratories in establishing their own reference ranges of provided parameters15. In addition, the variability of reference ranges of provided parameters could have occurred from factors such as; the difference of population, race, and environment15. The authors also studied HbA1c levels in males, females and age groups less than 40 years old and greater than 40 years old, and found that HbA1c levels are independent of gender (p=0.298). However, it varied among age groups. In our data HbA1c levels are higher among elderly age group (p=0.001).

The present results are different from a previous study performed in Thai population which found that gender had statistical significance11. In our study, the intra-assay CV of HbA1c were 2.6%, 1.9% and 1.6% for low, normal and high levels of controls , respectively. These intra-assay CVs were less than 3% according to the recommendation for laboratory analysis in the diagnosis and management of diabetes mellitus16.

The reference ranges for healthy individuals and the recommended values for optimal therapy in diabetic patients have to be revised and adjusted in accordance to the new reference range. "The various commercial assays need to adjust to the new international reference system for reference ranges and target values and to pace with the move towards standardization of analytical systems and harmonization of standards". It is recommended that all the results of HbA1c should be reported in both NGSP and IFCC methods not only to facilitate the physicians but also to avoid confusions in reported results. In addition, population based reference ranges should be established to provide better patient care services and to achieve the standardization requirements according to NCCLS recommendations14.

Reference

1. Consensus committee. Consensus statement on the worldwide Standardization of the hemoglobin A1C measurement. Diabetes care 2007; 30:2399-400.

2. Haddadinezhad S, Ghazaleh N. Relation of fasting and postprandial plasma glucose to glycosylated hemoglobin in diabetic patients. Rawal Med J, 2008;33:12-4.

3. Ahmed N, Jadoon SA, Khan RM, Mazahar-ud-Duha, Javed M. Type 2 diabetes mellitus: how well controlled in our patients. J Ayub Med Coll Abbottabad, 2008; 20:70-2.

4. Little RR, Roberts WL. A Review of Variant Hemoglobins Interfering with Hemoglobin A1c Measurement. J Diabetes Sci Technol, 2009; 3(3):446-51.

5. Nathan DM, Kuenen J, Borg R, Zheng H, Schoenfeld D, Heine RJ. Translating the A1C assay into estimated average glucose values.Diabetes Care, 2008;31:1473-8.

6. Bennett CM, Guo M, Dharmage SC. HbA(1c) as a screening tool for detection of Type 2 diabetes: a systematic review.Diabet Med, 2007; 24:333-43.

7. Nakagami T, Tominaga M, Nishimura R, Yoshiike N, Daimon M,Oizumi T, et al. Is the measurement of glycated hemoglobin A1c alone an efficient screening test for undiagnosed diabetes? Japan National Diabetes Survey. Diabetes Res Clin Pract, 2007;76:251-6

8. David BS. Carbohydrates. In: Burtis CA, Ashwood ER. Tietz textbook of clinical chemistry and Molecular Diagnostics, 4th ed. St. Louis: Saunders, 2006:837-901.

9. Randie R .Little, Curt L. Rohlfing. HbA1c Standardization: Background, Progress and Current Issues. Lab Medicine, 2009 40:368-373.

10. Herman WH, Ma Y, Uwaifo G, Haffner S, Kahn SE, Horton ES, Lachin JM, Montez MG, Brenneman T, Barrett-Connor E. Differences in A1c by race and ethnicity among patients with impaired glucose in the diabetes prevention program. Diabetes Care, 2007 ; 30:2453-7.

11. Charuruks N, Milintagas A, Watanaboonyoungcharoen P, Ariyaboonsiri C. Determination of Reference Intervals of HbA1C(DCCT/NGSP) and HbA1C (IFCC) in Adults. J Med Assoc Thai, 2005; 88: 810-6

12. Saaddine JB, Campagna AF, Deborah Rolka D, Narayan V,Geiss L, Eberhardt M, and Katherine M. Flegal KM. Distribution of HbA1c Levels For Children and Young Adults in the U.S. Third National Health and Nutrition Examination Survey. Diabetes Care, 2002, 25 : 1326-1330.

13. Dwamena NK. Glycosylated Hemoglobin (HbA1C) Levels in a Male Kuwaiti Population. The Kuwait Medical Journal, 2001, 33 (1): 26-28.

14. Hoelzel W, Weykamp C, Jeppsson J, Miedema K, Barr JR, Goodall I, et al. IFCC Reference System for Measurement of Hemoglobin A1c in Human Blood and the National Standardization Schemes in the United States, Japan, and Sweden: A Method-Comparison Study . Clinical Chemistry. 2004;50:166-174.

15. National Committee for Clinical Laboratory Standards. How to define and determine reference intervals in the clinical laboratory: approved guideline, NCCLS document C28-A and C28-A2 Villanova, PA: NCCLS 1995, 2001.

16. Fucharoen S, Winichagoon P, Piankijagum A. Standardization on laboratory diagnosis of thalassemia and abnormal hemoglobin. Southeast Asian J Trop Med Public Health .1999; 30: 90-8.
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Author:Ali, Syed Khawar; Khan, Dilshad Ahmed; Khan, Farooq Ahmed
Publication:Pakistan Armed Forces Medical Journal
Article Type:Report
Geographic Code:9PAKI
Date:Dec 31, 2011
Words:2082
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