Abstract
The use of unconventional biological materials in human trace element studies has increased in terms of published research studies. The aim of present study was to develop and validate the use of teardrop fluid for determining trace element levels in the human body. No study has been published in this area yet. This is a new non-invasive approach in the possible early diagnosis of the pathogenesis of type 2 diabetes.
Human teardrop fluid samples were obtained from Karbala (Iraq) (n = 111) healthy individuals and with type 2 diabetes (n = 44); and London (UK) healthy individuals (n = 18). The levels of V, Cr, Mn, Fe, Cu, Zn, As, Sr and Cd were determined using an inductively coupled plasma mass equipped with collision cell technology for polyatomic ion correction (ICP-MS).
Discriminate function analysis (DFA) was carried out to determine the set of variables that discriminated between the trace elements in teardrop fluid samples from healthy individuals and diabetic patients.
The trace element levels of human teardrop fluid are similar for many elements to that reported for human blood serum in the literature. This is interesting since they have different physiological functions, although overall they are mainly water containing electrolytes (∼ 90 %) and solids (antibodies, hormones, etc). In general, for the study groups in Karbala, Iraq, significantly higher teardrop fluid levels of Mn and Sr were found in type 2 diabetic patients when compared with healthy individuals (evaluated using an F-test and a two-tailed t-test). The levels of V, Cu and As were found to be significantly higher (P < 0.05) in healthy individuals than type 2 diabetic patients. Although the levels of Fe and Zn were slightly higher in type 2 diabetic patients than healthy cases, the differences were not statistically significant (P > 0.05). Cr and Cd were found to have similar levels for both study groups. Significantly higher teardrop fluid levels of V, Cr, Mn, Fe, Zn, As and Sr were found in healthy individuals from Karbala (Iraq) when compared with those from London (UK). In contrast, the levels of Cd observed to be significantly higher in London (UK) than Karbala. No statistical difference was found for Cu between the two healthy groups.
Discriminate analysis showed that human teardrop fluid V, Mn, Zn, As, Sr and Cd levels could be used to discriminate between healthy and type 2 diabetes study groups in Karbala, Iraq (83 % of cases correctly classified).
The use of human teardrop fluid for determining the trace element levels of human health conditions has been evaluated. Trace elemental levels are like that for blood serum which is widely used as an invasive method for assessing human health conditions. Sample collection for teardrop fluid is non-invasive and the application has potential for determining the trace element levels in healthy individuals and disorder conditions (like type 2 diabetes) in countries where cultural and gender sensitivity are issues with respect to the collection methods used for other body fluid samples.