PRE-ANALYTICAL VARIATION IN GLUCOSE CONCENTRATION DUE TO ATMOSPHERIC TEMPERATURE & CLOT IN BLOOD SPECIMENS

Pre-Analytical Laboratory Errors in Glucose Concentration

Abstract

Objective: To determine the effect of temperature and contact of clot with serum on laboratory results of glucose concentration in blood.
Study Design: Quasi-experimental study.
Place and Duration of Study: December 2014 to August 2015 at the laboratory of Shoaib Hospital, Fateh Jang, Attock Pakistan.
Material and Methods: Samples were collected for estimation of blood glucose (Random) concentration from patients reporting to the hospital. Blood specimens (n=94) of such volunteers were analyzed for glucose level. Each sample was put up in five tubes. When the blood clotted the serum from tube-1 was analyzed for glucose level within 30 minutes. In tube-2 & tube-3 serum was kept for 24 hours at room temperature & refrigerator temperature respectively before glucose estimation. In tube-4 & tube-5 serum was not separated from clot and kept at room temperature & refrigerator temperature respectively before glucose estimation. The value of tube 1 was taken as reference value for comparison with other parts of the specimen. The equipment used for blood glucose level estimation was semi auto chemistry analyzer (Rayto, China). The kit used for analysis was Glucose – Liquizyme (Germany).
Results: The difference between the mean reference value (tube-1) and refrigerated serum without clot (tube-3) was 4.63 mg/100 ml while that of unrefrigerated portion (tube-2) had a difference of 10.68 mg/100 ml. The mean of unrefrigerated (tube-4) and refrigerated (tube-5) portions of serum kept with the clot had difference of 42.05 mg/100 ml and 25.84 mg/100 ml respectively. The fall in the blood glucose level in all (n=94) the samples in the tube number 3 (serum separated & kept at refrigerated temperature) was 4.63 mg/100 ml ± 3.68 (Mean ± SD) and it ranged from 0 to 20 mg/100 ml whereas fall was maximum in the tube number 4 (serum with clotted blood & kept at room temperature) was 42.04 mg/100 ml ± 10.61 (Mean ± SD) and it ranged from 13 to 82 mg/100 ml. The sample in tube 3 provided the best results as compared to all the other tubes (p=<0.0001). When the serum was kept with clot there was significantly lesser fall when the sample was kept at refrigerated temperature (tube 4) than at room temperature (ube 5) (p=<0.0001). When comparing the fall in blood glucose in sample kept at room temperature but clot separated (tube-2) with sample kept at refrigerated temperature but clot was not separated (tube-5) there was a significantly less fall in glucose in tube-2 (p=<0.0001) indicating that reduction factor of clot is more contributor than the temperature.
Conclusion: There is maximum resistance in fall in glucose level after 24 hours when the blood sample was kept at refrigerated temperature & clot was removed before preservation. If refrigeration facilities are not available, it would be appropriate to remove clot before preservation at room temperature to get the consistent results as far as possible.