Effect of changes in laboratory light intensity on biochemistry and haemogram analysis

Introduction

Laboratory measurements always contain errors and uncertainties. It is not possible to perform a chemical analysis that is completely error-free and certain [1]. Laboratory errors typically occur in the pre-analytical or post-analytical phases, and less often during the analytical phase [2]. The level of uncertainty is a range of values given alongside a measurement or test result that are attributable to the measured magnitude [3]. The most important factor limiting the accuracy and sensitivity of an analytical method is the presence of extraneous and unwanted signals called “noise”, which overlap with the analytical signal to be measured. Chemical, instrumental and environmental noise is encountered in any analysis method that makes use of an instrument for measurement [4]. Chemical noise includes undetected variations in temperature or pressure that affect the position of the chemical equilibrium, and changes in light intensity that affects photosensitive materials. Environmental noise covers numerous sources of electromagnetic radiation. These include alternating current power lines, firing systems in gasoline engines, arc switches, brushes in electric motors, radio and TV stations, illumination and ionospheric distortion [4]. Changes in optical radiation can affect both optical and potentiometric sensors. If the optical sensor is based on the use of a spectrophotometer, the ambient light should be kept constant [5]. In this study, we aimed to investigate the effects of changes in laboratory light intensity on chemistry tests and whole blood analyses.

Materials and methods

Results

Chemistry results before and after increase in light intensity. There were no statistically significant differences in the photometric analyser readings for FBS, ALB, TP, AMYL, CK, AST, ALT, GGT, LDH, BUN, UA, UIBC, TBIL, direct bilirubin, MG, P, calcium, TG, cholesterol and LDL-C vs HDL-C in 195 and 1,168 lux luminous environments. The changes between the values reported in the pre- and post-experimental biochemical tests of LIP, ALP, CREAT, iron, CK, GGT, LDH and direct bilirubin were 11.3, 2.2, 2, 1.2, 2.7, 2.9, 2.2, and 2.5%, respectively. However, a statistically significant difference was found in the analysis results of the LIP, ALP, CREAT and iron chemistry tests (p<0.001, p=0.003, p=0.001 and p<0.001, respectively) (Table 1). The lipase, alkaline phosphatase, creatinine, iron and biochemistry tests were sensitive to changes in laboratory light intensity, but these changes were at clinically acceptable levels. Results for whole blood analyses performed before and after increase in light intensity. There was no statistically significant difference in the haematology analyser results for WBC Count, RBC Count, HB, HCT, MCV, MCH, MCHC, RDW-SD, RDW-CV, NEUTS (ANC), LYMPHS (ALC), MONOS, EOS and BAS when the tests were performed in 195 and 1,168 lux luminous environments. However, a statistically significant difference was found in the PLT parameter of the whole blood analysis (p=<0.001) (Table 2). Again, the PDW, MPV, P-LCR and PCT parameters could not be measured in a 1,168 lux luminous environment. Our data reveal that the platelet reading is sensitive to changes in laboratory light intensity and this change is at clinically unacceptable levels. This result is clinically significant because PLT is one of the determining parameters in the decision to administer platelet suspension treatment to a patient.

Discussion

The ion-sensitive field-effect transistor (ISFET) is one of the most popular electrical biosensors. Traditionally called a pH sensor, an ISFET is used to measure the ion concentrations (H+ or OH−) of a solution. In general, enzymes FETs are based on a similar principle, but rely on the binding of an analyte to a sensor such that the concentration of hydrogen ions during an enzymatic reaction is proportional to the substrate level. To date, various enzyme FETs have been developed to detect numerous analytes, such as glucose, urea, creatinine, protein, and TG. Ito observed that the long-term stability of ISFETs was strongly influenced by exposure to a fluorescent light. He repeatedly performed deviation tests by switching the light on and off at light intensities ranging from 800 to 1,500 lux and found that the deviation was higher at light intensities above 1,000 lux [6]. Ito’s study may explain why the LIP, ALP, CREAT and iron readings in or study exhibited a statistically significant difference in 195 and 1,168 lux luminous environments. When the results of pre- and post-experimental chemistry tests were compared using a non-parametric Wilcoxon test, only the LIP, ALP, CREAT and iron tests showed significant differences, while there was no significant difference in the CK, GGT, LDH and BILD tests. It is worth noting that the non-parametric Wilcoxon test does not compare mean values, but yields results by sorting. When we compared the percentage of changes in the LIP, ALP, CREAT and iron test results to the clinically acceptable limit values described by Ricós et al. [7]. We observed that the changes were within the clinically acceptable limits. The Sysmex XT-2000i automated haematology analyser uses the principle of impedance with hydrodynamic focussing to assess erythrocyte and platelet numbers. Large cells, such as erythrocytes and leukocytes, produce a relatively large signal and are counted by a method that uses an aperture of 100 µm in diameter. Since the volumes of the platelets range from 2 to 30 µm, which is between 1/40 and 1/3 of the size of a RBC, the resistance they provide is lower. Therefore, to increase the signal produced by platelets, it is necessary to reduce the size of the aperture (70–50 µm) and to increase the current flowing through the opening. However, in this context, the noise signal produced by blood particles and the natural electronic background noise is very close to the signal produced by platelets [8]. This may explain why there was a statistically significant difference in PLT, PDW, MPV, P-LCR and PCT parameters in 195 and 1,168 lux environments, while the WBC and RBC parameters were not affected. When we compared the percentage of change in the PLT parameter in our study (188%) to the clinically acceptable limit values of Ricós et al. [7] (16.5%), the percentage of change was found to be unacceptable. This change in the PLT parameter is clinically significant, because the PLT count is one of the determinant parameters in deciding whether to give platelet suspension treatment to a patient [9]. Our study shows that the PLT parameter is sensitive to changes in laboratory light intensity and this change is within the clinically unacceptable limits. This study shows that, similar to temperature and humidity, light intensity may be a significant source of noise affecting the accuracy of biochemical analyses in the laboratory. It is important to note that this study analysed a small number of chemistry and whole blood analysis results, which may not be sufficient to confirm that changes in laboratory light intensity do indeed affect the test results. Future investigations on this topic should ensure that the sample size is large enough to perform parametric statistical analyses. Analytical performance criteria (accuracy, precision, range, linearity, recovery, detection limit, interference, blind reading, specificity and sensitivity) should be determined for analyses performed in 195 and 1,168 lux luminous environments. Further studies are needed to confirm the effect of changes in laboratory light intensity on whole blood and chemistry analyses.