Inaccurate results of laboratory testing are mostly caused by errors in the preanalytical phase. The aim of this retrospective study is monitoring, documenting and preventing errors in the pre-analytical phase in order to provide better health care for patients. The study has been done from 2017 to 2021 and involves monitoring, documenting and preventing errors with aspect to phlebotomy in clinical biochemical laboratory of primary health care, in Students Health Protection Institute. Errors are classified in accordance with IFCC recommendation as quality indicators: insufficient sample volume, inappropriately labeled sample and sample damage. The study has shown that the most common errors are insufficient sample volume and sample damage (0.97 %). Inappropriately labeled samples were significantly lower and completely eliminated during period of study (2017 was 0.34 %, 2021 was 0 %; p<0.01). No significant decrease in number of sample damage (2017- 0.50 % - 2021- 0.30 %) was shown and insufficient sample volume errors (2017- 0.43% - 2021-0.32%) were constantly persisting during the period of study. Through permanent improvement and application of quality management system (QMS), implementation of certification and accreditation of laboratories according to the ISO15189, 2018- (QM / QA) standards for medical laboratories the entire laboratory testing process can be improved. Implementation of LIS (Laboratory Information System), the standard for POCT-ISO22870: 2006 Point of care testing, along with clear transparent and available procedures, errors in the pre-analytical phase can be minimized. Special attention should be paid on errors that continue to exist in the study. With more accurate, precise and valid results, correct and fast diagnosis, satisfied patients can be achieved with a smaller number of errors in pre-analytical phase and the principle of cost benefit can be achieved following the guideline: “no blood sample is better than a bad blood sample”.

1. M. Zaninotto, M. Plebani, “Understanding and managing interferences in clinical laboratory assays: the role of laboratory professionals,” Clin. Chem. Lab. Med., vol. 58, no. 3, pp. 350 – 356, Feb. 2020.
   DOI: 10.1515/cclm-2019-0898
   PMid: 31622245
2. M. Plebani, M. Laposata, G. D. Lundberg, “The brain-to-brain loop concept for laboratory testing 40 years after its introduction,” Am. J. Clin. Pathol., vol. 136, no. 6, pp. 829 – 833, Dec. 2011.
   DOI: 10.1309/AJCPR28HWHSSDNON
   PMid: 22095366
3. M. Plebani, “Quality Indicators to Detect Pre-Analytical Errors in Laboratory Testing,” Clin. Biochem. Rev., vol. 33, no. 3, pp. 85 – 88, Aug. 2012.
   PMid: 22930602
   PMCid: PMC3428256
4. G. Lippi et al., “Error rates during blood collection in emergency departments and outpatient clinics: Results of a prospective multicenter study,” Clin. Chim. Acta., vol. 445, pp. 91 – 92, May 2015.
   DOI: 10.1016/j.cca.2015.03.022
   PMid: 25818240
5. N. Nikolac, “Lipemia: causes, interference mechanisms, detection and management,” Biochem. Med. (Zagreb), vol. 24, no. 1, pp. 57 – 67, Feb. 2014.
   DOI: 10.11613/BM.2014.008
   PMid: 24627715
   PMCid: PMC3936974
6. M. Plebani, “Exploring the iceberg of errors in laboratory medicine,” Clin. Chim. Acta., vol. 404, no. 1, pp. 16 – 23, Jun. 2009.
   DOI: 10.1016/j.cca.2009.03.022
   PMid: 19302995
7. G. Lippi, “Preanalytical quality improvement. In pursuit of harmony, on behalf of European Federation for Clinical Chemistry and Laboratory Medicine (EFLM) Working group for Preanalytical Phase (WG-PRE), Clin. Chem. Lab. Med., vol. 53, no. 3, pp. 357 – 370, Feb. 2015.
   DOI: 10.1515/cclm-2014-1051
   PMid: 25490032
8. M. Plebani, “Errors in clinical laboratories or errors in laboratory medicine?,” Clin. Chem. Lab. Med., vol. 44, no. 6, pp. 750 – 759, May 2006.
   DOI: 10.1515/CCLM.2006.123
   PMid: 16729864
9. M. Plebani, “The detection and prevention of errors in laboratory medicine,” Ann. Clin. Biochem., vol. 47, no. 2, pp. 101 – 110, Mar. 2010.
   DOI: 10.1258/acb.2009.009222
   PMid: 19952034
10. A. M. Simundic et al., “Joint EFLM-COLABIOCLI Recommendation for venous blood sampling,” Clin. Chem. Lab. Med., vol. 56, no. 12, pp. 2015 – 2038, Nov. 2018.
    DOI: 10.1515/cclm-2018-0602
    PMid: 30004902
11. B. Caruso, C. Bovo, G. C. Guidi, “Causes of preanalytical interferences on laboratory immunoassays – a critical review,” EJIFCC, vol. 31, no. 1, pp. 70 – 84, Mar. 2020.
    PMid: 32256291
    PMCid: PMC7109499
12. J. Favresse, M. C. Burlacu, D. Maiter, D. Gruson, “Interferences with thyroid function immunoassays: clinical implications and detection algorithm,” Endocr. Rev., vol. 39, no. 5, pp. 830 – 850, Oct. 2018.
    DOI: 10.1210/er.2018-00119
    PMid: 29982406
13. L. Wauthier, M. Plebani, J. Favresse, “Interferences in immunoassays: review and practical algorithm,” Clin. Chem. Lab. Med., vol. 60, no. 6, pp. 808 – 820, Mar. 2022.
    DOI: 10.1515/cclm-2021-1288
    PMid: 35304841
14. J. Schiettecatte, E. Anckaert, J. Smitz, “Interferences in Immunoassays,” in Advances in Immunoassay Technology, N. H. L. Chiu, T. K. Christopoulos, Eds., Rijeka, Croatia: Intech, 2012, ch. 3, pp. 45 – 62.
    DOI: 10.5772/35797
15. J. Favresse et al., “D-dimer: preanalytical, analytical, postanalytical variables, and clinical applications,” Crit. Rev. Clin. Lab. Sci., vol. 55, no. 8, pp. 548 – 577, Dec. 2018.
    DOI: 10.1080/10408363.2018.1529734
    PMid: 30694079
16. G. Ward, A. Simpson, L. Boscato, P. E. Hickman, “The investigation of interferences in immunoassay,” Clin. Biochem., vol. 50, no. 18, pp. 1306 – 1311, Dec. 2017.
    DOI: 10.1016/j.clinbiochem.2017.08.015
    PMid: 28847718
17. A. M. Jones, J. W. Honour, “Unusual results from immunoassays and the role of the clinical endocrinologist,” Clin. Endocrinol., vol. 64, no. 3, pp. 234 – 244, Mar. 2006.
    DOI: 10.1111/j.1365-2265.2006.02439.x
    PMid: 16487430
18. G. Lima-Oliveira, D. Monneret, F. Guerber, G. C. Guidi, “Sample management for clinical biochemistry assays: are serum and plasma interchangeable specimens?,” Crit. Rev. Clin. Lab. Sci., vol. 55, no. 7, pp. 480 – 500, Nov. 2018.
    DOI: 10.1080/10408363.2018.1499708
    PMid: 30309270
19. G. Dimeski, “Interference testing,” Clin. Biochem. Rev., vol. 29, no. 1, pp. S43 – 48, Aug. 2008.
    PMid: 18852856
    PMCid: PMC2556582
20. M. Plebani, “Analytical quality: an unfinished journey,” Clin. Chem. Lab. Med., vol. 56, no. 3, pp. 357 – 359, Feb. 2018.
    DOI: 10.1515/cclm-2017-0717
    PMid: 28902617
21. F. G. Strathmann, M. M. Ka, P. M. Rainey, G. S. Baird, “Use of the BD vacutainer rapid serum tube reduces false-positive results for selected beckman coulter Unicel DxI immunoassays,” Am. J. Clin. Pathol., vol. 136, no. 2, pp. 325 – 329, Aug. 2011.
    DOI: 10.1309/AJCPZOFJ7KX5QMRW
    PMid: 21757607
22. M. Vogeser, C. Seger, “Irregular analytical errors in diagnostic testing - a novel concept,” Clin. Chem. Lab. Med., vol. 56, no. 3, pp. 386 – 396, Feb. 2018.
    DOI: 10.1515/cclm-2017-0454
    PMid: 28902615
23. R. Srivastava et al., “Reflex and reflective testing: efficiency and effectiveness of adding on laboratory tests,”Ann. Clin. Biochem., vol. 47, no. 3, pp. 223 – 227, May 2010.
    DOI: 10.1258/acb.2010.009282
    PMid: 20392754
24. D. Wang et al., “Effect of sampling time on estimates of thyroid-stimulating hormone, free thyroxine, and free triiodothyronine levels,” Scand. J. Clin. Lab. Invest., vol. 79, no. 7, pp. 459 – 462, Nov. 2019.
    DOI: 10.1080/00365513.2019.1626904
    PMid: 31526200
25. S. X. Soh, T. P. Loh, S. K. Sethi, L. Ong, “Methods to reduce lipemic interference in clinical chemistry tests: a systematic review and recommendations,” Clin. Chem. Lab. Med.,vol .60, no. 2, pp. 152 – 161, Nov. 2021.
    DOI: 10.1515/cclm-2021-0979
    PMid: 34773729
26. A. A. A. Ismail, “Identifying and reducing potentially wrong immunoassay results even when plausible and “not-unreasonable”,” Adv. Clin. Chem., vol. 66, pp. 241 – 294, 2014.
    DOI: 10.1016/b978-0-12-801401-1.00007-4
    PMid: 25344990
27. C. M. Sturgeon, A. Viljoen, “Analytical error and interference in immunoassay: minimizing risk,” Ann. Clin. Biochem., vol. 48, no. 5, pp. 418 – 432, Sep. 2011.
    DOI: 10.1258/acb.2011.011073
    PMid: 21750113
28. A. von Meyer, G. Lippi, A. M. Simundic, J. Cadamuro, “Exact time of venous blood sample collection - an unresolved issue, on behalf of the European Federation for Clinical Chemistry and Laboratory Medicine (EFLM) Working Group for Preanalytical Phase (WG-PRE),” Clin. Chem. Lab. Med., vol. 58, no. 10, pp. 1655 – 1662, Sep. 2020.
    DOI: 10.1515/cclm-2020-0273
    PMid: 32549131
29. A. Clerico et al., “A Black Swan in clinical laboratory practice: the analytical error due to interferences in immunoassay methods,” Clin. Chem. Lab. Med., vol. 56, no. 3, pp. 397 – 402, Feb. 2018.
    DOI: 10.1515/cclm-2017-0881
    PMid: 29220884