I have examined several hundred
laboratory process flowcharts and observed significant
variations in the same process flowcharted by two
different people using the same flowcharting style and
symbology! There are many flowcharting conventions, each
suited to a different role.
The simplest of these are so-called
procedure diagrams which rank the steps in a procedure
in a sequential manner from beginning to end. These are
usually linear charts read from the top down with the
names of the steps in the procedure listed inside
rectangular boxes. Depending on the complexity of the
procedure, these charts may contain conditional
sub-procedures based on a decision made by the operator
using some defined criteria. The most complex diagrams,
precedence diagrams, are commonly used to describe
complex models, assemblies or project structures. These
employ special symbol sets with the values of several
variables encoded within each symbol. The first type of
chart is too simple and the second type too complex to
flowchart most laboratory processes.
Before we begin to define a useful
flowcharting convention for laboratory process analysis
we need to define what constitutes a process. The one
that I use when lecturing on the subject is simple and
provides a good basis for flowcharting. Essentially, a
process is a set of related activities designed to
transform a set of well-defined inputs into a set of
desired outputs by consuming a given set of resources.
An example is a data entry process. The set of inputs
consists of the various types and states of data entry
forms. The transformational process includes a sequence
of conditional data entry activities, usually determined
by the type or state of the data entry form, that use
the resource data entry clerk to generate the desired
output -correctly entered data.
Essentially there are no more than
four key functions in any laboratory: Data entry,
specimen processing, analysis and result
entry/reporting. All other processes exist to support
these four main functions. The analytical function is a
collection of processes, each particular to the type of
analysis performed.
The
most common errors in flowcharting fall into one of the
following categories:
- Inconsistent level of detail
Parts of the chart decompose activities into
individual actions while other parts of the chart do
not
- Excessive detail
Many flowcharts show an excessive level of detail
making them difficult to analyze
- Disorganized flow
Nothing is more confusing than following arrows
moving in all directions over the chart
- Inaccurate flow
Sequential activities should be listed in the order
they are performed. Concurrent activities should be
charted side-by-side at the same level of the chart.
One of the keys to accurate
flowcharting is to determine at which points the process
starts and ends. Laboratories are notoriously myopic,
viewing their processes as essentially intramural in
nature. It is useful, however, to remember that many of
the factors that drive cost in the laboratory are
determined before the specimen arrives at the laboratory
receiving area. For this reason, it is often very useful
and informative to look outside the laboratory's walls
when analyzing a process. This is especially valuable
when evaluating information flow processes where
information is often generated by, and conveyed to,
external departments. Finally, avoid the tendency to
compartmentalize processes. Modern integrated
laboratories often involve processes that are
interrelated at several levels either by sharing a
common resource base or a set of common inputs.
A
good flowchart should contain the following
characteristics:
- Consistent level of detail
throughout the chart
- ppropriate level of detail
o keep highly complex process
flowcharts legible, drill down to sub-processes by
charting them on separate pages and using off-page
connectors to lead the reader to the appropriate
sheet.
- Logical, easy-to-follow flow
In flowcharting processes that flow
across multiple departments or which utilize multiple
resources use the column chart format. This is
sometimes called a swim lane flowchart. In this type
of chart, individual departments or resources are
listed in the sequence they interact with the process
across the top of the chart. The first department or
resource used is listed in the left column and the
last one listed in the right column. List the
individual activities performed by each department or
resource under its column. Data should flow up and
down and from left to right, keeping re-looping to a
minimum.
- Use simple, meaningful symbology.
There are no more than five primary
classes of activity in any laboratory process:
operations, reviews/inspections, decisions, wait
states and transports. Every activity performed in a
laboratory falls within one of these five classes of
activity. This is useful in arriving at a meaningful
symbol set for flowcharting.
- Accurately determine the start and
end points of the process and clearly identify them
on the chart.
In analyzing laboratory process, I
frequently use a flowcharting device called a workflow
ventilation diagram. This diagram specifically
concentrates on analyzing the utilization of labor in a
process. An example of a top-level workflow ventilation
diagram for a simple, multi-departmental specimen
processing and handling process is shown on the last
page of this article. Let's examine some of the features
of this type of flowchart.
Key labor-consuming activities are
charted in a columnar format with the columns
representing the departments that perform the
activities. Black-bordered lozenges indicate individual
workstations within each department. The use of a
lozenge to indicate a workstation indicates that
processing at that location continues on another
flowchart. This is used to keep the information needed
at this level of the flowchart down to a manageable
level. Following standard convention, work flows up and
down and from left to right whenever possible to make
the flowchart easy to read. The individual activities
are listed sequentially in the order they are performed
under the locations where the activities are performed.
The symbol set I use consists of
the following symbols:
This green-bordered cartouche which
clearly indicates the starting point for the process.
This bullet-nosed symbol indicates
at what level of the process specimens must wait for
an available human resource in order for processing to
continue. Wait states are not used to indicate
required incubations or machine wait states such as
centrifugation cycles. This helps me to evaluate the
number and location of points within a process when an
input must wait for an operator. Where the average
duration of a wait state is known, it is often encoded
within the wait state symbol.
This circle indicates points where
an operator must examine the state of the specimen in
order to determine how it is to be processed or
routed.
This gray-shaded lozenge indicates
when an operator must make a decision. Decision points
usually follow review/inspection points. You can
encode the decision criteria the operator uses to make
a decision on the chart.
- Labor-Consuming Operation
This square includes the name of the
activity along with the symbol. Because this chart is
specifically used to analyze labor utilization, only
labor-consuming activities are charted.
This small circle bisected by a
line, is a "housekeeping" symbol. It
organizes flow on the chart and indicates points where
flow divides or joins within a process without
requiring a decision to be made.
This large arrow symbol indicates
points within the process where an operator must
physically transport a specimen from one location to
another.
This red-bordered cartouche
indicates points where processing ceases.
Also encoded on the chart is the
following additional information:
These are encoded on the flow
arrows. This chart shows weekly volumes.
These are encoded below the name for
each activity. It indicates how many times the
activity is performed, on a weekly
basis in this case.
Click on chart to
enlarge
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