Indian Journal of Pathology and Microbiology
Home About us Instructions Submission Subscribe Advertise Contact e-Alerts Ahead Of Print Login 
Users Online: 498
Print this page  Email this page Bookmark this page Small font sizeDefault font sizeIncrease font size

  Table of Contents    
Year : 2020  |  Volume : 63  |  Issue : 4  |  Page : 678-680
Recapping error: A case of false positive result due to minuscule contamination by re-closure of vacutainer

1 Department of Transfusion Medicine, Jaypee Hospital, Sector 128, Noida, Gautam Buddh Nagar, Uttar Pradesh, India
2 Department of Laboratory Medicine, Jaypee Hospital, Sector 128, Noida, Gautam Buddh Nagar, Uttar Pradesh, India

Click here for correspondence address and email

Date of Submission01-Mar-2020
Date of Decision24-Jun-2020
Date of Acceptance27-Jun-2020
Date of Web Publication28-Oct-2020

How to cite this article:
Setya D, Pandey P, Ranjan S, Kumar D, Das S. Recapping error: A case of false positive result due to minuscule contamination by re-closure of vacutainer. Indian J Pathol Microbiol 2020;63:678-80

How to cite this URL:
Setya D, Pandey P, Ranjan S, Kumar D, Das S. Recapping error: A case of false positive result due to minuscule contamination by re-closure of vacutainer. Indian J Pathol Microbiol [serial online] 2020 [cited 2020 Nov 25];63:678-80. Available from: https://www.ijpmonline.org/text.asp?2020/63/4/678/299341

Dear Editor,

Laboratory services form an important cornerstone of any health care center. Despite advances, testing is still susceptible to various pre-analytical, analytical and post-analytical errors.[1] To improve the process, it is vital to survey all procedures and improve the testing process.[2],[3] During routine laboratory testing procedures, sealing and resealing of vacutainers is often necessary. Usually, caps are removed for processing of samples and they are recapped before storage or in between testing procedures to avoid spillage and contamination. In this correspondence, authors share their experience of a false positive anti-HIV I and II antibody result due to an unexpected, minuscule contamination by re-capping of vacutainer.

   Case Top

Vacutainer A was centrifuged in a table top centrifuge (Remi, Mumbai, India), uncapped and placed in a universal sample tray for HIV I and II antibody testing by first test (T1), a Chemiluminescence immunoassay (Vitros 3600 Immunodiagnostic system, Ortho Clinical Diagnostics, USA). Vacutainer B which had been received 20 minutes after vacutainer A, was processed in a similar manner. Due to an invalid result, vacutainer A was recapped and centrifuged again. Both samples A and B were now subjected to T1 with three other samples. Out of the total five samples, sample A and sample B both were reactive with different E ratios. As per strategy III B given by NACO for HIV testing [Figure 1], both samples were subjected to a second (T2) and third (T3) test. Repeat T1 was also performed using a secondary vacutainer received in hematology laboratory. Sample A gave ambiguous results which have been summarized in [Table 1].
Figure 1: NACO strategy/algorithm III B for HIV testing

Click here to view
Table 1: Results of all tests performed with sample A and Rsample A

Click here to view

   Root Cause Analysis Top

It was found that patient A was not a known case of retroviral disease. Patient was planned for an elective surgery and viral marker testing was being performed as a part of routine pre-anesthetic check-up. On the other hand, patient B was a known case of retroviral disease. Additionally, for resolution of discrepant results, western blot and viral load was performed for sample A, sample B and Rsample A.

At first, wrong-blood-in-tube (WBIT) was the only logical explanation. However, sample A and sample B were received from different collection centers. Exclusion of all plausible causes led us to recapping error. It was hypothesized that when sample A was recapped for repeat centrifugation, the vacutainer cap used was that of sample B. However, it was doubtful whether this tiny an amount of sample from vacutainer cap was enough to cause contamination.

   Intentional Recapping- the Experimental Proof Top

An experiment was planned to demonstrate the effect of minuscule contamination. Intentional recapping error using Rsample A and sample B (Esample A + B) was executed in duplicate. With the results, it was established that the reactive results obtained for sample A were false positive results due to contamination from the vacutainer cap of a reactive serum sample caused by recapping error.

   Corrective and Preventive Action (CAPA) Top

Identification of the source of error was followed by a corrective and preventive action. Corrective action included educating laboratory personnel about contamination of samples by recapping of vacutainers highlighting the fact that an invisible amount of sample in the vacutainer cap can also lead to contamination. Preventive action included procuring rubber corks for recapping instead of reusing vacutainer caps, discarding vacutainer caps immediately after uncapping, designating two separate areas in the laboratory for used and unused disposables and establishing a standard operating procedure for uncapping and recapping of vacutainers. An incident was raised by the department as a near miss event and correct reports of both the patients were released by the department.

Pre-analytical phase in blood sample testing is the phase where most errors take place in a laboratory and together, pre-analytical and analytical errors are responsible for more than half of the total errors encountered.[4],[5] These errors are largely due to human errors and are preventable. Establishing a training system, quality monitoring programs and timely interventions in conjunction can lead to a decrease in the number of these errors.[6],[7]

Wenk et al. described such a case of false positive anti-HIV antibody testing which was caused by use of a previously used disposable pipette or plastic tube cap which allowed the accidental transfer of serum.[8] This original article highlights an important fact that invisible contamination through disposables can lead to false positive test results and also that universal precaution guidelines and current guidelines for handling blood specimens do not address the problem of cross contamination due to which laboratories lack insight into the possible sources of contamination by minuscule samples.

Abundant literature is available about medical, legal, psychological and social issues associated with false-positive HIV test results, there is hardly any discussion about contamination as a cause of such results.[9] Such an error is more troublesome for tests which can multiply the contaminant, i.e., amplification techniques or culture.[10] The present case report highlights the contamination that can be caused by invisible residual serum in vacutainer caps, which was unexpected but it was proved with the results obtained by the experiment sample (Esample A + B) run in duplicate. This error compelled the laboratory to take certain measures that have been discussed as a part of preventive actions taken.

Prevention of sample contamination requires physical separation of used and unused disposables like pipette tips and vacutainer caps. Used disposables should be kept as far as possible from unused disposables and unused disposables should be kept shielded on the work station to prevent unintentional cross-contamination. Used vacutainer caps should be discarded as soon as the vacutainer is opened. There are various alternatives for recapping such as parafilm, a closure which is readily stretchable so as to fit with tubes of different sizes or a cap such as rubber cork.[11] Every laboratory should personalize procedures in order to prevent laboratory errors from reaching bedside.

Thus, minuscule contamination which is invisible to the naked eye can cause unexpected cross-contamination of test samples and hence measures must be taken by each laboratory to prevent errors caused by such contamination.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

   References Top

Astion ML, Shojania KG, Hamill TR, Kim S, Ng VL. Classifying laboratory incident reports to identify problems that jeopardize patient safety. Am J Clin Pathol 2003;120:18-26.  Back to cited text no. 1
Carraro P, Plebani M. Errors in a stat laboratory: Changes in type and frequency since 1996. Clin Chem 2007;53:1338-42.  Back to cited text no. 2
Rana SV. No preanalytical errors in laboratory testing: A beneficial aspect for patients. Indian J Clin Biochem 2012;27:319-21.  Back to cited text no. 3
Narayanan S. The preanalytic phase: An important component of laboratory medicine. Am J Clin Pathol 2000;113:429-52.  Back to cited text no. 4
Llopis MA, Bauça JM, Barba N, Álvarez V, Ventura M, Ibarz M, et al. Spanish Preanalytical Quality Monitoring Program (SEQC), an overview of 12 years' experience. Clin Chem Lab Med 2017;55:530-8.  Back to cited text no. 5
Li HY, Huang XN, Yang YC, Huang WF, Chen L, Song P, et al. Reduction of preanalytical errors in clinical laboratory through multiple aspects and whole course intervention measures. J Evid Based Med 2014;7:172-7.  Back to cited text no. 6
Kalra J. Medical errors: Impact on clinical laboratories and other critical areas. Clin Biochem 2004;37:1052-62.  Back to cited text no. 7
Wenk RE. Disposables as sources of preanalytical contamination and misdiagnosis. Am J Clin Pathol 1997;107:395-7.  Back to cited text no. 8
Sullivan JF, Kessler HA, Beverly ES. False-positive HIV test: Implications for the patient. JAMA 1993;269:2847.  Back to cited text no. 9
Persing DH, Smith TF, Tenover FC, White TJ. Diagnostic Molecular Microbiology: Principles and Applications. American Society for Microbiology. Washington, DC. 1993.  Back to cited text no. 10
DeVaughn DH. Inventor; Bio-Plas Inc, assignee. Stretchable cap for sealing and/or resealing blood drawing tubes and the like. United States patent US 4,542,833. 1985 Sep 24.  Back to cited text no. 11

Correspondence Address:
Divya Setya
Department of Transfusion Medicine, Histocompatibility and Molecular Biology, Jaypee Hospital, Sector.128, Noida - 201304, Gautam Buddh Nagar, Uttar Pradesh
Login to access the Email id

Source of Support: None, Conflict of Interest: None

DOI: 10.4103/IJPM.IJPM_202_20

Rights and Permissions


  [Figure 1]

  [Table 1]


    Similar in PUBMED
   Search Pubmed for
   Search in Google Scholar for
    Email Alert *
    Add to My List *
* Registration required (free)  

   Root Cause Analysis
    Intentional Reca...
    Corrective and P...
    Article Figures
    Article Tables

 Article Access Statistics
    PDF Downloaded6    
    Comments [Add]    

Recommend this journal