Diagnostic efficacy of hand-held digital refractometer for determining total serum protein in indigenous sheep of Pakistan

Abstract

The study was designed to ascertain the diagnostic efficacy of hand-held digital refractometer in determining total protein. The Sipli sheep (n=141) were grouped as per gender (females=99, males=29) and age (G1=up till 1 year, G2=from 1 to 2 years, G3=above 2 years). The results regarding the overall mean (±SE) values and RIs for the TPs attained through serum chemistry analyzer (TP1) and hand-held digital refractometer (TP2) were non-significantly (P≤0.05) different (59.2±1.6g/L and 59.8±0.5g/L, respectively). However, the RIs were quite different between the two TPs being 45.1-95.7g/L and 57.0-67.0g/L for TP1 and TP2, respectively. Similar results were seen for gender-wise and group-wise results. On the contrary, the results regarding correlation coefficient and logilinear regression showed a negative correlation between the two TPs (r=-0.0244) with an adjusted r-square of 0.059 (5.9% probability). Furthermore, the results for Cronbach alpha and intraclass correlation coefficient between TP1 and TP2 showed that the values for single measure and average values were lower between TP1 and TP2 being - 0.135 and −0.313. Bland and Altman test between TP1 and TP2 also showed a weak level of agreement between the two methods of detecting TP. A proportional bias on the distribution of data around the mean difference line was noticed between TP1 and TP2 (Mean= 0.5; 95% CI= 39.8 to −40.9) with a standard deviation of biasness being 20.58. In a nutshell, the hand-held digital refractometer cannot be used as an on-farm POCT device for determining serum TP in sheep. However, certain other models of refractometers with higher sensitivity and specificity may be utilized in future studies to establish these conclusions for other species of livestock.