Module 12
Managing supplies for a
tuberculosis laboratory performing culture
Purpose
To provide you with the knowledge and skills to order, stock
and maintain materials for the proper functioning of a TB
laboratory.
Prerequisite
modules
Modules 3 to 8
Module time
1 hour 20 minutes (including 40 minutes for the exercise)
Learning
objectives
At the end of this module, you will be able to
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list supplies required for culture;
explain ordering of supplies;
maintain proper records;
explain use of the stock book;
calculate supplies required;
inspect and verify supplies delivered;
explain storage of supplies.
Content outline
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Supply list for culture
•
Record-keeping: stock book use and importance
•
Calculation of supplies to order
•
Receipt of supplies
•
Storage and shelf- life of supplies
Handout and
exercises
Stock book
Exercise: Calculate laboratory supplies
LABORATORY SUPPLY SYSTEMS
Laboratory supply systems vary from country to country. Factors that affect how a
laboratory receives its supplies include whether the health care system is integrated or
vertical, whether the laboratory calculates its own needs and places its own orders, and
whether the laboratory receives orders based on calculations done at another level in the
health care system. A laboratory must be aware of the supplies required, of how to ensure
that required supplies are always available for its work, and of how to store such supplies.
SUPPLY LIST FOR CULTURE
The following is a list and the quantities of supplies required for performing culture of one
specimen (supplies for microscopy not included in detail):
Items
LJ media
Quantity
2
NaOH
0.003 litre
Sodium citrate
0.003 litre
NALC
0.003 litre
Na2HPO4
0.025 litre
KH2PO4
0.025 litre
Loops
1.2
Transfer pipettes
1.2
Falcon tubes
1.1
Cryotubes
1.1
Supplies requiring NTP specification
Certain supply items will depend on choices made by the NTP. These include:
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solid media used ( LJ/Ogawa/acid-buffered Ogawa medium);
reagents for the decontamination method (NaOH/NALC);
reagents for the DST method (proportion/resistance ratio/absolute concentration);
device used to inoculate media (metal wire or disposable loops or Pasteur pipettes).
SUPPLY STORAGE
Keep reagents in well-closed bottles and out of direct sunlight. Follow the manufacturer’s
instruction for correct storage (ambient temperature, 4 °C, –20 °C) and for the shelf-life.
Keep stock bottles inside a cabinet, unless they are made of dark glass or plastic. Label all
stock bottles containing reagents with names and dates of preparation. Old, as well as
improperly stored, reagents deteriorate and may not work effectively.
Keep media in the refrigerator, with screw-caps tightened to avoid excessive drying.
STOCK MANAGEMENT
Stock management means properly maintaining adequate supplies to ensure uninterrupted
service. It involves performing a stock count (physical inventory), maintaining proper
inventory records, determining how much to order, when to order, placing orders properly,
inspecting and verifying supplies received, and ensuring proper storage of stock.
Laboratory stock management ensures the availability of reagents, media and materials,
avoids the use of expired items and minimizes waste. The availability of high-quality culture
and DST testing services depends on the uninterrupted availability of essential supplies.
It is important to avoid under-stocking or over-stocking supplies. Under-stocking will result in
insufficient supplies for the tests you need to perform, which will interrupt the testing
process. The laboratory’s entire testing system could be seriously compromised until further
supplies are available.
Over-stocking causes different problems. Laboratories have limited space, which can be
overwhelmed by excessive stock; this may compromise safety and security. Excessive stock
also requires additional management, which wastes laboratory workers’ time. Over-stocking
can lead to deteriorated reagents and waste; the use of old reagents may compromise test
results.
Proper management of stocks is thus very important, and will ensure that only adequate
supplies are on hand.
RECORD-KEEPING: STOCK MANAGEMENT, STOCK BOOK
A stock count is performed to determine exactly what stock is on hand and how much. It
entails the physical counting of each item in the stock and it should be performed at the end
of each quarter. A designated person is responsible for performing this count and recording
the quantities of each item on a stock book.
Efficient stock management depends upon accurate record-keeping. Accurate records
ultimately save time. Proper inventory records help laboratory workers to determine their
patterns of consumption and estimate supplies for a year for budgeting purposes.
The stock book contains a list of all items in the store. It must be routinely updated when
orders are placed and received. It also serves as a reference for tracking orders that have
been placed but not received. The information on dates of ordering and of receipt of
supplies may help a laboratory to adjust the reserve quantities of supplies that are kept on
site to ensure uninterrupted testing.
CALCULATING SUPPLIES REQUIRED
Calculations for the supplies required for a TB laboratory can be based on the actual
number of specimens examined during a quarter and a stock count of supplies on hand.
Alternatively, supply calculations can be based on the positivity rate among TB suspects
examined.
A calculation based on work performed and a stock count may be more accurate since it
reflects the actual conditions at the laboratory, rather than an estimate of those conditions.
For culture, this calculation can be performed using a spreadsheet (see example below).
The number of exams performed at a TB laboratory in a quarter and the amount of each
item required for processing a specimen are determined. These two values give the
quantity of each item calculated for one quarter of operation. To this value, a reserve
quantity of each item is added to ensure continuity of testing. The reserve quantity can be
fixed at the amount of each item required for one quarter of operation but can be increased
or decreased depending on how reliable the order system is and how quickly supplies that
have been ordered are received.
The calculated quantity of each item for one quarter of operation plus the reserve gives an
accurate estimate of supplies actually required for one quarter. From that estimate, the
supplies already on hand (as determined from the physical inventory, i.e. the stock count)
are subtracted. The result, rounded up to the next order unit, is the quantity of items that
must be ordered to ensure uninterrupted testing during the next quarter of operation.
Number of cultures done in the region during the previous quarter (A): 1000
Item
Quantity
(litre)
needed
per
culture
(B)
Reagent Calculated
quantity requirements
(grams or for 3 months
litres) per
(litres or
litre
grams)
(C)
(D) = AxBxC
Reserve
quantity
for 3
months
Stock
on
hand
Calculated
request
(E) = D
(F)
(G) = D+E‒F
Actual
request
(rounded
up)
Order unit
Culture
LJ media
2
N/A
2000
2000
0
4000
40
NaOH
0.003
40
120
120
0
240
3
Sodium citrate
0.003
29
87
87
0
174
2
NALC
0.003
5
15
15
0
30
2
Na2HPO4
0.025
9.47
236.75
236.75
0
473.5
5
KH2PO4
0.025
9.07
226.75
226.75
0
453.5
5
Loops
1.2
N/A
1200
1200
0
2400
3
Transfer pipettes
1.2
N/A
1200
1200
0
2400
3
Falcon tubes
1.1
N/A
1100
1100
0
2200
22
Cryotubes
1.1
N/A
1100
1100
0
2200
3
Box of 100
tubes
Bottle
(100 g)
Bottle
(100 g)
Bottle
(25 g)
Bottle
(100 g)
Bottle
(100 g)
Box of 1000
loops
Box of 1000
pipettes
Box of 100
falcon tubes
Box of 1000
cryotubes
PLACING ORDERS, RECEIVING AND STORING SUPPLIES
To ensure the reliable delivery of supplies, orders must be placed properly and in line with
country-specific instructions. It is important to understand what contingency plans (both
regional and national) exist for times when stock is not available. Ordering supplies also
involves understanding the communications or feedback systems to the central level in
terms of the information that should be provided to central procurement or stores (e.g.
different seasonal consumption rates during winter or dry months).
When ordered items arrive at the laboratory, check to ensure that the delivery matches the
order and that items are in good condition. Label each item with the date of receipt (and
later, when the item is opened and used, the date must also be recorded). Where possible,
place items on shelves. Items should be stored in an orderly fashion, keeping like items
together. Store new shipments behind existing stock, ensuring that the oldest items are
stored in front so they will be used first. Store all stock items in a well-ventilated, clean, and
tidy room. Store the chemicals, media, and reagents away from direct sunlight – and
refrigerate them if necessary. Lastly, be sure to update the stock management records.
KEY MESSAGES
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Maintain an adequate inventory at all times to ensure uninterrupted service.
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Do not let any item run out.
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Never order more than you require in the next quarter.
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Record and account for all items in the inventory.
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Always inspect a new shipment before accepting it.
Module 12: Review
Find out how much you have learned by answering these questions.
What is supply management?
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Why is a physical stock count necessary?
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Why is it important to maintain inventory records?
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How do you calculate supplies required?
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Why must orders be inspected and verified?
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Why must supplies be stored properly?
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STOCK BOOK
Item name:________________________
Physical count
(units)
Date of physical
count
Quantity (units)
requested
Unit__________________
Date
requested
Quantity
received
Date
received
Total stock in
hand