Abstracts at the 9thAPCCB, New Delhi, India by Singapore participants.

SK Ong1, HP Wei2, SFY Li 2, TC Aw1; (1) Department of Laboratory Medicine, National University Hospital, Singapore, (2) Department of Chemistry, University of Singapore, Singapore.

(This abstract was chosen for oral presentation)

This report summarises the clinical utility of CE-L1 system(CE Resources, Singapore) that use fused-silica column(25m m I.D.), autosampler to inject 1.7nL of diluted sample(1:15 water), a UV detector at 214nm and recorder(DataApex, Czech Republic) to analyse serum proteins. A constant voltage of 30kV for 8 minutes at 25° C was applied. Buffer contained 0.11M boric acid, 66mM sodium carbonate and 0.5mM polyethylene glycol(mw 10,000) and column wash was 1M sodium hydroxide. In this study a normal serum sample(SPE) and an abnormal patient serum(PS) with a paraprotein band as detected by agarose gel electrophoresis(Beckman, USA) were used. The CV ranges were intra-day 2.0-25.0% and inter-day 5.5-17.1% The data for 5 zones as detected by CE-L1 are as tabulated:

Zone

(N=80)

Retention time (mean ± sd) minutes

Area relative (mean ± sd)%

 

SPE

PS

SPE

PS

Albumin

6.74± 0.15

6.84± 0.27

59.36± 3.26

45.74± 4.88

Alpha-1

6.14± 0.13

6.24± 0.81

7.48± 0.81

6.59± 1.09

Alpha-2

5.64± 0.13

5.61± 0.19

9.73± 0.83

6.97± 1.17

Beta

5.17± 0.10

5.24± 0.16

9.19± 1.26

7.50± 1.28

Gamma

4.48± 0.09

4.73± 0.17

14.92± 1.32

37.07± 3.14

The above data show that retention time for both samples (SPE and PS) are similar in all 5 zones. The relative(area)% of all 5 zones measured in normal(SPE) is within the reference values cited(reference1) and gamma peak was detected (37.07%) in the patient with myeloma (PS). Further studies using samples from myeloma patients are being investigated. In conclusion, we find that the CE-L1 capillary electrophoresis system precise, fast, easy to use and its economical usage of reagents an advantage in today’s cost-effective laboratory.

Reference1: Petrini C et al "Serum proteins by capillary zone electrophoresis: Approaches to the definition of reference values" Clin Chem Lab Med 1999;37(10):975-980.

 

S Saw and TC Aw Department of Laboratory Medicine, National University Hospital, Singapore

TSH receptor (TSH-R) antibodies are useful tools in the diagnosis and management of hyperthyroidism in Graves disease. We examined the performance of a newly available ELISA kit from RSR Ltd (Cardiff, Wales) and compared it to our current receptor assay based on 125I-labeled TSH precipitation technique (RSR Ltd). We reviewed the results of 76 patients routinely requesting TSH-R. Linear correlation produced a relationship of ELISA = 8.415(RIA)-2.679, r=0.84. Six patients were negative by RIA and positive by ELISA. Between-run imprecision (n=9) obtained a CV of 7.2% and 12.9% for negative and positive kit controls respectively. We established our own cut-off using 112 blood donor specimens obtaining a 95% cut-off at 1.75 IU/L. Using this cut-off we obtained a sensitivity of 95.1% and a specificity of 97.3% (Graves disease n=61 and normal n=111). However, using the manufacturers recommended cut-off at 1.0 IU/L a sensitivity of 47.7% and a specificity of 4.9% were obtained. Technically the performance of the assay shows improvement compared to the radioreceptor technique. However, with the new standardisation (90/672) of the TSH receptor assay a laboratory must validate the cut-off for their own population to ensure that their normal population are not being over diagnosed.

 

 

 

1MS Wong, 2GI Lim, 1TC Aw, 3LS Chew.

1Department of Laboratory Medicine, National University Hospital, Singapore; 2School of Life Sciences and Chemical Technology, Ngee Ann Polytechnic, Singapore; 3Diabetes Centre, Alexandra Hospital, Singapore.

The pathogenesis and complications in diabetes mellitus (DM) have been postulated to be secondary to oxidative stress and compromised antioxidant states. In this study, we aim to determine the antioxidant status in diabetic individuals.

Antioxidant status was determined on 217 diabetic patients (61 type 1 and 156 type 2) and 221 controls using the Total Antioxidant Status(TAS) kit (Randox Laboratories, UK). Intra-day and inter-day imprecision were <3% and <4.5% respectively.

The diabetic group had significantly lower TAS values than controls (1.33 mmol/L vs 1.41 mmol/L, p<0.0001). TAS levels <1.0 mmol/L were seen in twenty diabetic individuals (9.2%) but only five controls (2.3%). Significant differences in BMI, WHR, triglycerides, HDLC and HbA1c were observed between the type 1 DM and type 2 DM groups. Moreover, type 1 patients had lower TAS than type 2 patients (1.25 mmol/L vs 1.36 mmol/L, p=0.0053). Diabetic individuals on simvastatin for hyperlipidaemia also had higher TAS concentrations (p=0.0183) compared to diabetic patients on fenofibrate and normolipidaemic diabetic patients.

Our study shows that diabetic individuals, especially type 1, have compromised TAS states. Our results also suggest that lipid lowering using simvastatin may be more beneficial than fenofibrate in optimising TAS status in this high-risk group.

 

  • EVALUATION OF THE ROCHE HITACHI MODULAR D/P SYSTEM.

J.H. Chu, M.G. Ou, C.W. Tse and R.C. Hawkins.

Department of Pathology and Laboratory Medicine, Tan Tock Seng Hospital,

Objectives: We evaluated the performance of 27 Roche serum assays (Alb, ALP, ALT, Amy, AST, Ca, Cl, Chol, CK, Crea, Fe, GGT, Glu, K, Lact, LDH, Mg, Na, Phos, T.Bil, Tg, TP, UA and Urea) on the Hitachi D/P Modular system and compared them to the Hitachi 917.

Methods: Day-to-day imprecision on the Modular system was determined using 3 levels of commercial controls assayed up to 34 days. Inaccuracy was assessed using patient samples and the results were analysed using Deming model linear regression (x=Hitachi 917, y=Modular, mean bias = Modular – Hitachi 917).

Results: Imprecision on the Modular was better than or equal to the Hitachi 917 in all 27 chemistries. No clinically significant difference in results was seen. Assay linearity met or exceeded manufacturer’s claims. No significant sample carryover was detected. Parameters for selected chemistries: %CV range, regression line, n, r, mean bias; ALT: 1.0-4.4%, y = 1.08x – 1.51, 90, 1.00, 2.2; Chol: 0.7 – 1.2%,

y = 1.00x + 0.01, 63, 1.00, 0.01; Crea: 2.3 – 7.0%, y = 0.97x – 0.10, 89, 1.00, -4.1; Na: 0.7 – 1.0%,

y = 1.04x – 6.20, 56, 0.96, -0.1.

Conclusion: The analytical performance of the Modular D/P system is satisfactory and with a throughput four times that of the Hitachi 917, this makes the Modular D/P system ideal for a very busy laboratory with a high workload.

 

 

  • EVALUATION OF VITROS Eci FREE tHYROXINE, THYROID STIMULATING HORMONE AND TOTAL THYROXINE MEASUREMENTS ON UMBILICAL CORD BLOOD SAMPLES.

1Tan E T H, 2Hawkins R.W. 1KK Women’s and Children’s Hospital, 2 Department of Pathology and Laboratory Medicine, Tan Tock Seng Hospital

Objective: Cord blood TSH (thyroid stimulating hormone) is used as the screening test for primary hypothyroidism in Singapore. This study examined the performance of the Ortho-Clinical Diagnostics (OCD) free thyroxine (FT4), thyroid stimulating hormone and total thyroxine (TT4) assays on the Vitros ECi immunoassay analyzer using umbilical cord serum samples.

Materials and Methods: Imprecision was assessed using two levels of commercial control over 20 days. Agreement with the ECi and the Abbott Axsym system was assessed using 100 cord blood samples.

Results: Within-run CVs: FT4: 2.1% (8.03 pmol/L), 1.8% (48.52); TSH: 2.7% (0.07 mIU/L), 3.0% (15.97); TT4: 1.5% (38.4 nmol/L), 1.1% (219). Between-run CVs: FT4: 4.6% (8.0 pmol/L), 3.3% (47.9); TSH: 6.1% (0.07 mIU/L), 3.7% (15.6); TT4: 4.5% (38.5 nmol/L), 4.7% (223.9). Comparison parameters using Deming Model linear regression (mean bias = ECi - Axsym): FT4: ECi = 1.769 * Axsym-5.93, r = 0.870, mean bias = 4.27; TSH: ECi = 1.097 * Axsym+0.056, r = 0.991, mean bias = 1.06; TT4: ECi = 0.869 * Axsym-4.25, r = 0.955, mean bias = -19.8

Conclusion: The OCD Vitros ECi offers fast, precise analysis of FT4, TSH and TT4. Use of the ECi TSH assay would increase the TSH cutoff from 25 to 27.5 mU/L. Significant biases between the ECi and the Axsym for FT4 and TT4 require instrument-specific reference intervals to be used for cord blood samples. Given the present use of cord TSH as the primary screening test, the ECi is a satisfactory alternative to the Axsym for neonatal screening on cord blood.

 

  • AGREEMENT BETWEEN FREE T3 ASSAYS IN non-thyroidal illness.

R C Hawkins Department of Pathology and Laboratory Medicine, Tan Tock Seng Hospital

Objective: Interpretation of free triiodo-thyronine (FT3) levels in non-thyroidal illness (NTI) is complicated by differences in assay methodology. This study examined the effect of NTI on FT3 measurement using OCD Vitros ECi, Abbott Axsym, Roche Elecsys 2010 and Bayer ACS 180 immunoassay systems

Methods: FT3 levels were measured on 120 ambulatory health screening subjects and on 80 inpatients from intensive care units (NTI group). Reference intervals obtained from the ambulatory group were applied to the NTI populations and the subsequent categorisation of results (low, normal, high) compared between assays using a kappa test.

Results: The 95% reference intervals were: ECi 6.2-9.2, Axsym 2.2-4.8, Elecsys 4.8-8.7 and ACS 3.8-5.5 pmol/L. Ambulatory and NTI medians were: ECi: 7.6, 5.7; Axsym 3.5, 1.8; Elecsys 6.6, 2.9; ACS 4.6, 2.8. Applying the above reference intervals to the NTI population, % low and high results were: ECi: 66, 9, Axsym 70,0; Elecsys 86, 0; ACS 85, 0. Kappa: ECi vs Axsym 0.23, ECi vs ACS 0.46, ECi vs Elecsys 0.26, Axsym vs ACS 0.49, Axsym vs Elecsys 0.59, ACS vs Elecsys 0.77.

Conclusion: This study demonstrates the variable agreement between different FT3 assays in NTI. All assays showed consistently low FT3 levels except for the ECi assay where elevated FT3 may be seen. Clinicians should be aware that not all commercially available assays show consistently low FT3 levels in NTI.