Accurate laboratory diagnosis forms the cornerstone of effective patient management, particularly in the field of clinical microbiology where results directly influence antimicrobial therapy, infection control measures, and patient outcomes. The total testing process in laboratory medicine is traditionally divided into three phases: pre-analytical, analytical, and post-analytical. Among these, the pre-analytical phase is the most vulnerable to errors, accounting for nearly 60–70% of total laboratory errors, even in well-established healthcare systems [1,2].

The pre-analytical phase in microbiology encompasses a series of critical steps, including patient preparation, appropriate specimen selection, correct timing of collection, aseptic collection techniques, proper labeling, use of suitable containers, storage conditions, and timely transportation to the laboratory [3]. Errors occurring at any of these steps can significantly compromise specimen integrity, reduce pathogen viability, alter microbial load, or introduce contaminants, thereby leading to false-negative or misleading results [4].

Unlike biochemical or hematological investigations, microbiology samples are highly susceptible to pre-analytical variables because microorganisms are living entities whose survival depends on environmental conditions such as temperature, oxygen tension, transport media, and time to processing [5]. For example, delayed transport of specimens may lead to overgrowth of commensals or death of fastidious organisms, while improper collection techniques may result in contamination, rendering culture results uninterpretable [6].

Common pre-analytical errors in microbiology include collection of samples after initiation of antimicrobial therapy, inadequate sample volume, use of inappropriate containers or transport media, improper labeling or missing patient details, leakage during transport, and prolonged transit time to the laboratory [7,8]. Blood culture contamination, poorly collected sputum samples, and improperly collected urine specimens are among the most frequently encountered problems in routine laboratory practice [9].

These errors not only affect diagnostic accuracy but also have significant clinical and economic implications. Erroneous results may lead to delayed or inappropriate treatment, prolonged hospital stay, increased healthcare costs, and unnecessary use of broad-spectrum antibiotics, thereby contributing to antimicrobial resistance [10,11]. In addition, rejected or repeat samples cause inconvenience to patients and increase workload for healthcare personnel.

Despite their significant impact, pre-analytical errors often receive less attention compared to analytical quality control measures. In developing countries, factors such as heavy patient load, limited resources, inadequate training of healthcare workers, and lack of standardized protocols further increase the likelihood of such errors [12]. There is a relative paucity of Indian data systematically evaluating the magnitude and pattern of pre-analytical errors specifically in microbiology laboratories.

Therefore, this observational study was undertaken to identify and analyze the frequency and types of pre-analytical errors in microbiology samples received at a tertiary care hospital over a defined study period. Understanding these errors is essential for implementing targeted corrective measures, improving laboratory quality indicators, and ultimately enhancing patient care.

Study Design

Observational, laboratory-based study.

Study Period

1 September 2022 to 31 March 2023

Study Setting

Department of Microbiology, Tertiary Care Teaching Hospital.

Study Material

All clinical microbiology samples received during the study period, including:

• Blood
• Urine
• Sputum
• Pus and wound swabs
• Body fluids
• Stool samples

Inclusion Criteria

• All routine microbiology samples received during the study period
• Samples submitted for culture and sensitivity or microscopy

Exclusion Criteria

• Repeat samples from the same patient on the same day
• Samples received after laboratory working hours without proper storage

Assessment of Pre-Analytical Errors

Each sample was assessed at the time of receipt for pre-analytical errors based on standard laboratory guidelines. Errors were categorized as:

1. Improper sample collection technique
2. Insufficient sample volume
3. Improper labeling or missing details
4. Delayed transport to laboratory
5. Use of inappropriate container
6. Leakage or contamination

Data Collection and Analysis

Data were recorded in a structured proforma and analyzed using descriptive statistics. Results were expressed as percentages and proportions.

The present observational study evaluated microbiology samples received during the study period from 1 September 2022 to 31 March 2023 to identify and analyze pre-analytical errors. A total of 1,240 microbiology samples were assessed for various types of pre-analytical errors at the time of receipt in the laboratory.

Overall Frequency of Pre-Analytical Errors

Out of the 1,240 samples received, 186 samples (15.0%) demonstrated one or more pre-analytical errors, while 1,054 samples (85.0%) were received without any detectable pre-analytical issues.

Table 1. Overall frequency of pre-analytical errors

Distribution of Types of Pre-Analytical Errors

Among the 186 samples with pre-analytical errors, the most common error identified was improper sample collection (34.9%), followed by insufficient sample quantity (21.5%) and delayed transport to the laboratory (18.3%).

Table 2. Distribution of pre-analytical errors by type (n = 186)

Sample-Wise Distribution of Pre-Analytical Errors

Pre-analytical errors were most frequently observed in blood samples (32.8%), followed by urine samples (29.6%) and sputum samples (18.3%).

Table 3. Sample-wise distribution of pre-analytical errors

*Other samples include body fluids, stool, and miscellaneous specimens.

Multiple Errors in a Single Sample

Out of the 186 samples with errors, 152 samples (81.7%) showed a single pre-analytical error, while 34 samples (18.3%) had more than one pre-analytical error.

Table 4. Distribution of number of errors per sample

Figure 1 depicts the overall distribution of microbiology samples with respect to pre-analytical errors.

Figure 2 demonstrates the distribution of different pre-analytical errors observed in the study population.

Figure 3 shows the distribution of pre-analytical errors according to the type of microbiology sample.

Pre-analytical errors represent a major challenge in laboratory medicine and are recognized as the most common source of laboratory inaccuracies. In the present observational study, 15.0% of microbiology samples received during the study period demonstrated one or more pre-analytical errors. This finding is consistent with earlier reports, which have documented pre-analytical error rates ranging from 10% to 20% in clinical microbiology laboratories [1,2].

The predominance of errors in the pre-analytical phase highlights the vulnerability of this phase, particularly in microbiology, where specimen quality and viability of organisms are crucial for accurate diagnosis. Unlike analytical errors, pre-analytical errors are largely human-dependent and occur outside the direct control of the laboratory, often during specimen collection and transport [3].

In the present study, improper sample collection (34.9%) was the most common pre-analytical error observed. Similar findings have been reported by Lippi et al. and Plebani, who identified improper collection techniques as the leading cause of specimen rejection and inaccurate results [4,5]. Poor aseptic techniques during blood collection, collection of sputum samples contaminated with saliva, and inadequately collected urine specimens were frequently encountered issues. These errors can result in contamination, false-positive cultures, or failure to isolate the causative pathogen [6].

Insufficient sample quantity (21.5%) was the second most frequent error in this study. Adequate sample volume is essential, particularly for blood cultures and body fluid samples, as low volume significantly reduces pathogen detection rates [7]. Under-filled blood culture bottles and inadequate volumes of cerebrospinal or pleural fluid were common causes, reflecting a need for improved awareness among healthcare workers regarding minimum volume requirements.

Delayed transport of samples to the laboratory accounted for 18.3% of errors in the present study. Timely processing is critical in microbiology, as prolonged transport can lead to overgrowth of commensals, death of fastidious organisms, and altered colony counts [8]. Similar observations have been reported in studies from tertiary care centers, where transport delays were attributed to logistical issues and lack of dedicated sample transport systems [9].

Improper or incomplete labeling was observed in 14.0% of error samples, posing a serious risk to patient safety. Mislabeling or missing patient identifiers can lead to sample rejection, incorrect reporting, and potential diagnostic errors [10]. International laboratory quality standards emphasize proper labeling as a key patient safety indicator, underscoring the need for strict adherence to labeling protocols [11].

Use of inappropriate containers accounted for 11.3% of pre-analytical errors in this study. Incorrect containers or absence of appropriate transport media can compromise organism survival and interfere with culture results [12]. Urine samples submitted in non-sterile containers and swabs sent without transport media were common examples, consistent with findings from other Indian studies [13].

Sample-wise analysis revealed that blood and urine samples accounted for the highest proportion of pre-analytical errors. This observation aligns with previous studies, which have reported higher error rates in frequently requested and high-volume samples [14]. Blood cultures are particularly prone to collection-related errors, while urine samples are often affected by improper collection techniques and container issues.

The occurrence of multiple errors in 18.3% of samples further emphasizes the cumulative impact of pre-analytical lapses. Multiple errors in a single specimen significantly reduce the likelihood of obtaining a reliable result and often necessitate repeat sampling, increasing patient discomfort and laboratory workload [15].

Overall, the findings of this study highlight the urgent need for targeted interventions to reduce pre-analytical errors in microbiology laboratories. Regular training programs, standardized operating procedures, sample collection manuals, and close collaboration between clinicians, nursing staff, and laboratory personnel are essential to improving specimen quality and ensuring accurate microbiological diagnosis.

Pre-analytical errors in microbiology samples are common and largely preventable. Addressing these errors through staff training, standardized collection protocols, and effective communication between clinical and laboratory teams can improve the quality of microbiological diagnosis and patient care.

Recommendations

• Regular training programs for healthcare workers
• Use of standardized sample collection guidelines
• Timely transport of samples to the laboratory
• Periodic audits of pre-analytical practices

Limitations

• Single-center study
• Did not assess impact of errors on clinical outcomes

Acknowledgements

The authors acknowledge the support of laboratory staff and clinicians for their cooperation during the study period.

Conflict of Interest

None declared.

1. Plebani M. Errors in clinical laboratories or errors in laboratory medicine? Clin Chem Lab Med. 2006;44(6):750–759.
2. Lippi G, Chance JJ, Church S, et al. Preanalytical quality improvement: from dream to reality. Clin Chem Lab Med. 2011;49(7):1113–1126.
3. World Health Organization. Laboratory Quality Management System: Handbook. Geneva: WHO; 2011.
4. Lippi G, Bassi A, Brocco G, et al. Preanalytical error tracking in a laboratory medicine department: results of a 1-year experience. Clin Chem. 2006;52(7):1442–1443.
5. Plebani M. The detection and prevention of errors in laboratory medicine. Ann Clin Biochem. 2010;47(Pt 2):101–110.
6. Baron EJ, Miller JM, Weinstein MP, et al. A guide to utilization of the microbiology laboratory for diagnosis of infectious diseases. Clin Infect Dis. 2013;57(4):e22–e121.
7. Cockerill FR, Wilson JW, Vetter EA, et al. Optimal testing parameters for blood cultures. Clin Infect Dis. 2004;38(12):1724–1730.
8. Miller JM, Holmes HT. Specimen collection, transport, and storage. In: Manual of Clinical Microbiology. 11th ed. Washington DC: ASM Press; 2015. p. 19–31.
9. Chawla R, Goswami B, Tayal D, Mallika V. Identification of the types of preanalytical errors in the clinical chemistry laboratory: 1-year study at G.B. Pant Hospital. Lab Med. 2010;41(2):89–92.
10. Wagar EA, Stankovic AK, Raab S, Nakhleh RE. Specimen labeling errors: a Q-probes analysis of 147 clinical laboratories. Arch Pathol Lab Med. 2008;132(10):1617–1622.
11. International Organization for Standardization. ISO 15189: Medical laboratories – Requirements for quality and competence. Geneva: ISO; 2012.
12. Garcia LS. Clinical Microbiology Specimen Management. Clin Lab Med. 2013;33(1):1–18.
13. Jain A, Chitnis DS. Pre-analytical errors in microbiology laboratory. Indian J Med Microbiol. 2007;25(4):348–349.
14. Goswami B, Singh B, Chawla R, Mallika V. Evaluation of errors in a clinical laboratory: a one-year experience. Clin Chem Lab Med. 2010;48(1):63–66.
15. Lippi G, Plebani M. Identification and management of preanalytical errors in laboratory testing. Clin Chem Lab Med. 2009;47(3):235–246.