Presumptive blood test using Hemastix® with EDTA in archaeology

A presumptive test is a rapid screening method that indicates the possible identity of a substance. To ensure a presumptive test is reliable, accurate and replicable, it has to be validated. In this paper we present a method validation for the cost-effective, presumptive blood test, Hemastix® with sodium ethylenediaminetetraacetic acid (EDTA) specifically for archaeology and buried residues. Hemastix®, a haemoglobin specific chemical reagent test strip (Hb-CRTS), was used with the addition of a chelating agent (EDTA) which increases the specificity of this test. It was conducted using a collection of 146 substances (plant, animal, metal compounds, chemical solutions including blood), 6 experimentally degraded samples, 177 experimental artefacts, 238 reference samples (on microscope slides) and 39 mixtures of substances. We also compared the Hemastix® and Hemastix® with EDTA test to two other Hb-CRTSs (URS-10 and Chemstrip® 10MD) and two additional presumptive tests, the tetramethylbenzidine (TMB) test and the phenolphthalein test. The results demonstrate that Hemastix® is the most specific, sensitive and cost-effective presumptive test evaluated which can be substituted with any other Hb-CRTS. Although the longevity and survival of haemoglobin on archaeological artefacts requires further investigation, the method validation described here supports Hemastix® performed with EDTA as being a reliable presumptive test for the presence of residual blood on buried artefacts.