Specimen Collection

Proper specimen collection

Correct patient ID, labeling, appropriate specimen type, and volume, proper PPE, proper transport, and timely processing → ensures accurate results and optimal diagnostic sensitivity

Improper specimen collection

Includes mislabeling, wrong specimen type, contamination, delayed transport, incorrect temperature, or PCR inhibitors, leading to specimen rejection, false results, or degraded nucleic acids.

Consequences of improper collection

False negatives, false positives, specimen rejection, delayed diagnosis, and potential patient harm.

Nasopharyngeal swab materials

A synthetic fiber swab, viral transport medium, and appropriate PPE are required for proper collection.

Nasopharyngeal swab technique

Insert the swab parallel to the nasal floor into the nasopharynx, rotate gently, hold briefly, then place it in transport medium to ensure an adequate sample.

Purpose of proper NP swab technique

Ensures sampling of high viral load area to maximize diagnostic yield and reduce false negatives

Multiplex PCR

A molecular technique that amplifies multiple targets in a single reaction using multiple primer sets

Multiplex PCR clinical use

Used in respiratory viral panels to detect multiple pathogens simultaneously

Influenza preferred specimen

Nasopharyngeal swab in VTM or UTM due to high viral load in upper respiratory tract

Tuberculosis preferred specimen

Early morning sputum because it contains highest concentration of mycobacteria

Chlamydia and Gonorrhea preferred specimen

First catch urine in males and vaginal swab in females to maximize organism recovery from urogenital epithelium

HIV preferred specimen

Blood plasma from EDTA or PPT tube for viral load testing and confirmation

HCV preferred specimen

Blood serum in SST tube to detect circulating viral RNA

HSV preferred specimen

Swab of active lesion or CSF depending on disease site because virus localizes to lesions or CNS

HPV preferred specimen

Cervical vaginal or anal brush in liquid based cytology medium targeting infected epithelial cells

Enterovirus preferred specimen

Depends on site including NP or OP swab stool or CSF because virus localizes differently based on disease presentation

Parvovirus preferred specimen

Blood in adults and amniotic fluid in fetus due to circulation in blood and fetal infection

Malaria preferred specimen

Blood in EDTA tube because parasites infect red blood cells

CMV preferred specimen

Saliva or urine in newborns and blood in immunocompromised patients due to viral shedding and circulation

General short term storage

Most specimens stored at 2 to 8 (

∘Cis a metr and processed as soon as possible to prevent degradation

General long term storage

Specimens stored at minus 70 degrees Celsius or lower for long term stability