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Differential Time to Positivity

Item Value
Approval req'd? No
Available Stat? No
Test code P060 & P061
Test group Bacterial culture
Performed by Microbiology
In House Availability Daily, all shifts
Method Culture
Collection Instructions For detailed instructions, see nursing manual.

Peripheral vein and CVC line samples must be obtained within 15 minutes of each other.

The volumes of blood obtained from the peripheral vein & from the CVC must match. (e.g. if only 12 mLs is obtained from peripheral stick, obtain only 12 mLs from CVC).

Draw peripheral blood sample first since the amount of blood obtained will determine how much is obtained from the CVC.

Inoculate one set of aerobic & anaerobic bottles with the peripheral sample, dividing the volume in half for each bottle. Label bottles as "peripheral" and submit with a microbiology requisition (if applicable) for a DTTP Peripheral Blood Culture.

Inoculate a second set of aerobic & anaerobic bottles with the line sample, dividing the volume in half for each bottle. Label bottles as "line" and submit with a microbiology requisition (if applicable) for a DTTP Central Blood Culture.

Put all 4 bottles and requisitions (if applicable) in the same specimen bag and send to the lab.
Container type Two sets of paired blood culture bottles (BD BACTEC Plus Aerobic and Lytic Anaerobic)
Amount to Collect Adults: 40 mL total (20 mL for each set / 10 mL for each bottle)
Pediatrics: Collect blood sample amount according to weight for EACH set:
< 1 kg = 1 mL for aerobic only (0.5 ml for neonates < 72h old)
1 – 5 kg = 2 mL total (1 mL for each bottle)
5 – 15 kg = 3 mL total (1.5 mL for each bottle)
15 – 40 kg = 6 mL total (3 mL for each bottle)
>40 kg = 10 mL total (5 mL for each bottle)
Sample type Whole blood
Preferred volume Adults: 40 mL total (20 mL for each set / 10 mL for each bottle)
Pediatrics: Collect blood sample amount according to weight for EACH set (see "Amount to Collect" above)
Min. Volume Adults: 20 mL total (10 mL for each set / 5 mL for each bottle)
Pediatrics: Draw 1.0 mL minimum for culture (0.5 ml for neonates < 72h old) when collecting aerobic only (standard). If both aerobic and anaerobic needed, instill minimum of 1 mL in each bottle when collecting.
UCSF Rejection Criteria Samples that are not collected per "Collection Instructions"
Processing notes 1. Maintain samples at room temperature.
2. Both peripheral and central blood cultures, collected within 15 minutes of each other are submitted. More than one type of central blood culture may be submitted. Each set should be labeled as peripheral or central. Physician will order DTTP Peripheral Blood Culture and DTTP Central Blood Culture.
3. If unsuitable collection, complete a credit form and indicate reason NOTTP (DTTP culture not performed due to improper collection. Test requires peripheral and central line blood draws, collected within 15 minutes of each other.)
4. Accession one set and then the other(s).
5. Send all bottles to China Basin in one bag.
6. If the time from collection to loading bottles on the instrument is more than 12 hours, give the bottles to a CLS to subculture before loading.
7. Load all bottles into the instrument at the same time.

See Peripheral and Central Blood Culture processing notes for more information.
Normal range No growth
Critical value Inpatient results only. After hours outpatient results will be phoned the following morning.
Gram stain results from the first positive blood culture on a patient will be phoned.

Additional calls only made if > 7 days have elapsed since first call or a different organism is identified.
Synonyms catheter tip; catheter infection; blood culture
Stability 36 hours at room temperature
Turn around times 6 days
Additional information If organisms grow in the sample drawn through the line at least two hours earlier than from the peripheral blood, then the line is considered to be the source of infection.
CPT coding 87040
LOINC code 600-7
Last Updated 6/30/2017 12:35:44 PM
Entry Number 1117
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