Application of Statistics to Evaluate Iranian Analytical Laboratories Proficiency: Case of Aflatoxins in Pistachio

Document Type : Research Paper


1 IBB, University of Tehran

2 Marjaan Khatam, Training, Research & Q.C. Lab. Services, Tehran 1415633341, Iran


The aim of this study was to evaluate the utility of a proficiency testing program among limited number of local laboratories as an alternative to the IUPAC/CITAC guide on proficiency testing with a limited number of participants, specially where international schemes are not accessible. As a sample scheme we planned to determine aflatoxins (B1, G1, B2, G2, total) in Iranian pistachio matrix. A part of naturally contaminated pistachio sample was tested for sufficient homogeneity by a competent laboratory and then homogenized sub-samples were distributed among participants all across the country. The median of participants’ results was selected as assigned value. Student t-test was applied to show there is no significant difference between assigned and mean values of homogeneity test results obtained by the competent laboratory. Calculated z-scores showed that 6 out of 8 results in aflatoxin B1, 7 out of 8 results in aflatoxin B2, 5 out of 8 results in aflatoxin G1, 7 out of 8 results in aflatoxin G2 and 6 out of 9 results in aflatoxin total were in satisfactory range. Together our studies indicate that the approach described here is highly cost efficient and applicable for quality assurance of test results when there is no access to international proficiency testing providers.


[1] G. Hudler, Magical Mushrooms, Mischievous Molds, Princeton University Press, Princeton, NJ, 1998.
[2] ISIRI 5925, Food and Feed-Mycotoxins-Maximum tolerated level, 1380.
[3] Commission regulation (EC) 1152/2009, Imposing special conditions governing the import of certain foodstuffs from certain third countries due to contamination risk by aflatoxins and repealing Decisions 2006/504/EC
[4] I. Kuselman, M. Belli, S. Elison, A.Fajgelj, U. Sansone, W. Wegscheider, Accred. Qual. Assur. 12 (2007) 563.
[5] D. Park, H. Njapau, R. Coker, In: M. Miraglia, H. Van Egmond, C. Brera, J. Gilbert (Eds.), Mycotoxins and phycotoxins developments in chemistry, toxicology and food safety,  Alaken Inc., Colorado, United States, 1998.
[6] ISO/IEC 17025, General requirements for the competence of testing and calibration laboratories, 2005.
[7] M. Thompson, S. Ellison, R. Wood, Pure Appl. Chem. 78 (2006) 145.
[8] ISO 13528, Statistical methods for use in proficiency for testing by interlaboratory comparison. International Organization Standardization, Geneva, 2005.
[9] ILAC G13, Guidelines for the requirements for the competence of providers of proficiency testing schemes. International Laboratory Accreditation Cooperation, Sydney, 2007.
[10] M. Belli, S. Ellision, A. Fajgelj, I. Kuselman, U. Sansone, W. Wegscheider, Accred. Qual. Assur. 12 (2007) 391.
[11] I. Kuselman, A. Fajgelj, Pure Appl. Chem. 82 (2010) 1099.
[12] S. Wong, Accred. Qual. Assur. 16 (2011) 539.
[13] FAPAS Proficiency Testing Protocol for Organisation and Analysis of Data. Sixth edition, 2002.
[14] M. Thompson, Analyst 125 (2000) 385.