Cases & Commentaries

The Result Stopped Here

Commentary By Michael Astion, MD, PhD

The Case

A 91-year-old female was transferred to a
hospital-based skilled nursing unit from the acute care hospital
for continued wound care and intravenous (IV) antibiotics for
methicillin-resistant Staphylococcus aureus (MRSA)
osteomyelitis of the heel. She was on IV vancomycin and began to
have frequent, large stools.

The attending physician ordered a test for
Clostridium difficile on Friday, and was then off for the
weekend. That night, the test result came back positive. The lab
called infection control, who in turn notified the float nurse
caring for the patient. The nurse did not notify the physician on
call or the regular nursing staff. Isolation signs were posted on
the patient's door and chart, and the result was noted in the
patient's nursing record. Each nurse who subsequently cared for
this patient assumed that the physician had been notified, in large
part because the patient was receiving vancomycin. However, it was
IV vancomycin (for the MRSA osteomyelitis), not oral vancomycin,
which is required to treat C. difficile.

On Monday, the physician who originally ordered
the C. difficile test returned to assess the patient and
found the isolation signs on her door. He asked why he was never
notified and why the patient was not being treated. The nurse on
duty at that time told him that the patient was on IV vancomycin.
The float nurse, who had received the original notification from
infection control, stated that she had assumed the physician would
check the results of the test he had ordered. Due to the lack of
follow-up, the patient went three days without treatment for C.
, and continued to have more than 10 loose stools
daily. Given her advanced age, this degree of gastrointestinal loss
undoubtedly played a role in her decline in functional status and
extended hospital stay.

The Commentary

Communication failures are a common cause of
potential and actual adverse events in a variety of clinical
settings.(1-3) The
primary problem in this case was failure to adequately communicate
an abnormal laboratory result. Proper handling of the result would
have led to proper treatment and prevented patient harm.

Before considering the laboratory's role in this
error, it's worth reviewing other factors that contributed to this
incident. First, the physician ordered a C. difficile test
but failed to look up the test result. Physicians are responsible
for following up on tests they order. However, failure to do so
represents a common noncognitive error—an unconscious lapse
in an automatic behavior.(4,5)
Noncognitive errors are frequently related to fatigue, work
overload, and interruptions. This particular event occurred on a
Friday, as the physician left for the weekend. The timing increased
the likelihood of error, since proper handling of the laboratory
result required coordination between the ordering physician and the
covering team. Structured sign-outs that include "to-do" lists (eg,
follow-up on an important radiographic or laboratory test result)
may reduce the risk of lapses such as occurred here [ see related commentary ].

The second error was that the float nurse assumed
incorrectly that the ordering physician had knowledge of the test
result. Therefore, after receiving the abnormal result from
infection control, she did not relay it to staff who could have
acted on it. This type of communication failure probably occurs
more frequently with float staff, since they tend to know less
about the diligence and other habits of coworkers. In general,
assumptions of this type, especially in the context of ambiguous
roles and hierarchical differences, underlie many communication
failures in health care, as well as in other high-risk industries
such as aviation.(4)

The third error was that all subsequent nursing
staff assumed mistakenly that intravenous vancomycin was adequate
therapy. Addressing this particular error through an education
effort would be possible but unlikely to prevent any of the other
miscommunications or more systemic errors involved in this

In this case, the laboratory's communication
process would be considered a "systems problem" or latent error. However,
optimal protocols regarding notification of "panic" values
represent a complicated issue in laboratory medicine. Panic values
are also known as critical values, or more accurately as "alert"
values, since some reflect errors requiring immediate correction
rather than clinical conditions requiring immediate treatment. The
Clinical Laboratory Improvement Amendments (CLIA) governing U.S.
laboratory practice require that:

The laboratory must develop and follow written procedures for
reporting imminent life-threatening laboratory results or panic
values. In addition, the laboratory must immediately alert the
individual or entity requesting the test or the individual
responsible for utilizing the test results when any test result
indicates an imminent life-threatening condition.(6)

The law does not state which tests or test values
should be included in a panic value policy, nor does it stipulate
the types of personnel appropriate for communicating or receiving
the results.(7)

In practice, a core group of tests (Table) appear on
the panic value list of most institutions; beyond that
institutional practices vary greatly.(7-9) For
any test, however, there is substantial variability regarding what
constitutes a panic value. Nearly all institutions will have alert
values for glucose, sodium, potassium, hemoglobin, hematocrit, and
platelets, among others, but the specific panic thresholds for
these tests vary from one institution to another. In principle, the
optimal choice of a particular lab test as a potential alert and
the selection of panic thresholds for that test depend on the
clinical consequences of false positive and false negative alert
values. In practice, short-term considerations related to available
resources and institutional tradition likely play important roles
in determining these choices.

There is also considerable variability regarding
who actually receives results. A survey of 623 laboratories in the
United States revealed that, for inpatients, laboratory personnel
relayed panic values to nurses 40% of the time, and ward clerks
more than 30% of the time. The ordering physician or physician on
call was only reached 12% of the time.(8) Thus,
third parties, who are not direct care providers, play a
significant role in communicating panic and other laboratory
values. That appears to have occurred here since laboratory staff
called infection control staff, who called a float nurse, who
failed to notify appropriate unit staff.

Breakdown in panic value procedures has not been
widely researched, but previous studies and experience suggest that
it is a relatively frequent problem.(10,11)
Three common active errors in panic value
procedures are the failure of laboratory staff to call the value,
the failure of a third party to communicate the result to a direct
care provider, and failure of the direct provider to act on the
results in a timely manner. A significant source of latent error is
a panic value policy that poorly fits the needs of the

Computer alerting systems, which automatically
detect panic values and notify an appropriate care provider, can
improve communication of panic values and patient
outcomes.(12-14) One
study showed that a computer alerting system for panic values
increased the fraction of inpatients who received appropriate care
and reduced the length of hospital stay.(12)
Another computer alerting system automatically paged covering
physicians with panic laboratory values and reduced delays in
delivering appropriate treatment.(13)

For microbiology, most institutions consider
positive blood cultures, cerebrospinal fluid cultures, and Gram's
stains from cerebrospinal fluid (CSF) as panic values. The fraction
of institutions that include a positive test for C.
toxin on its list of panic values is unknown, but
surveys suggest it is less than one third.(7)
It is common practice, however, for laboratory staff to report
positive C. difficile tests to the hospital infection
control team to help the team prevent spread by ensuring compliance
with isolation procedures and other precautions. On the other hand,
hospital infection control usually has no responsibility to contact
a treating physician with the result of the patient's test.

Would the legal system deem the laboratory's
performance in this case to be below the standard of care? In
making this determination, the key questions would be (i) whether
the involved laboratory failed to follow its own panic value
procedure, and (ii) if the institution lacked any policy for a
particularly common panic result. For example, an institution that
had no panic value procedure for positive cultures from
cerebrospinal fluid might be deemed negligent in the setting of a
bad outcome. In my judgment, the handling of the positive test
result for C. difficile in this case was not below the
standard of care, because the laboratory did not violate its own
internal policy (since C. difficile was not on its panic
value list), and because it did enter the result in the laboratory
information system and contact infection control.

Take-Home Points

  • Physicians are responsible for tracking
    the results on laboratory tests they order. Checklists and other
    interventions aimed at decreasing lapses in concentration can
    prevent forgetting about ordered tests.
  • Panic value procedures are designed to
    rapidly communicate laboratory results associated with
    life-threatening emergencies. These procedures are limited in that
    they sometimes fail, and they include only a small subset of
    clinically significant laboratory results.
  • Ideally, hospitals should strive for a
    communication environment where care team members are free to
    question each other's knowledge. This is a challenging task, but
    would eliminate many preventable errors.

Michael Astion, MD,
Associate Professor
Director, Reference Laboratory Services
Department of Laboratory Medicine
University of Washington


1. Sutcliffe K, Lewton E, Rosenthal MM.
Communication failures: an insidious contributor to medical
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2. Kluger MT, Bullock MF. Recovery room
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3. Fordyce J, Blank FS, Pekow P, et al. Errors in
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4. Shojania KG, Wald H, Gross R. Understanding
medical error and improving patient safety in the inpatient
setting. Med Clin North Am. 2002;86:847-67.[ go to PubMed ]

5. Reason JT. Human Error. New York, NY:
Cambridge Univ Press; 1990.

6. Medicare, Medicaid and CLIA programs;
regulations implementing the Clinical Laboratory Improvement
Amendments of 1988 (CLIA)--HCFA. Final rule with comment period.
Fed Regist. 1992;57:7002-186.[ go to PubMed ]

7. Emancipator K. Critical values: ASCP practice
parameter. American Society of Clinical Pathologists. Am J Clin
Path. 1997;108:247-53.[ go to PubMed ]

8. Howanitz PJ, Steindel SJ, Heard NV. Laboratory
critical values policies and procedures: a College of American
Pathologists Q-Probes study in 623 institutions. Arch Pathol Lab
Med. 2002;126:663-9.[ go to PubMed ]

9. Lum G. Critical limits (alert values) for
physician notification: universal or medical center specific
limits. Ann Clin Lab Sci. 1998;28:261-71.[ go to PubMed ]

10. Tate KE, Gardner RM. Computers, quality, and
the clinical laboratory: a look at critical value reporting. Proc
Annu Symp Comput Appl Med Care. 1993; 193-7.[ go to PubMed ]

11. Kuperman GJ, Boyle D, Jha A, et al. How
promptly are inpatients treated for critical laboratory results? J
Am Med Inform Assoc. 1998;5:112-9.[ go to PubMed ]

12. Tate KE, Gardner RM, Weaver LK. A
computerized laboratory alerting system. MD Comput.
1990;7:296-301.[ go to PubMed ]

13. Kuperman GJ, Teich JM, Tanasijevic MJ, et al.
Improving response to critical laboratory results with automation:
results of a randomized controlled trial. J Am Med Inform Assoc.
1999;6:512-22.[ go to PubMed ]

14. Tate KE, Gardner RM, Scherting K. Nurses,
pagers, and patient-specific criteria: three keys to improved
critical value reporting. Proc Annu Symp Comput Appl Med Care.
1995; 164-8.[ go to PubMed ]


Table. Example Critical Values For Some Common
Laboratory Tests

(Lab Test)


Common qualifications or





Serum Glucose

>500 mg/dL

High value could have lower threshold in
newborns (eg, >200 mg/dL)

Serum Sodium

>160 mEq/L

High value could have lower threshold
(eg, >152 mEq/L)

Serum Potassium

>6.0 mEq/L

Either value could have slightly
different threshold

Serum Bicarbonate

>=40 mEq/L

Either value could have slightly
different threshold

Serum Calcium (total)

>13.0 mg/dL

Either value could have slightly
different threshold

Serum Bilirubin, Newborn (under 30 days

Not applicable

>=12.0 mg/dL

High value could have higher threshold
(eg, >15 mg/dL)

White Blood Cell Count


>50 x

Low value could be specified in terms of
absolute neutrophil count (eg, ANC -9/L)

High value could have threshold as high as 100 x

Thresholds commonly vary across settings (inpatient vs. outpatient)
and patient populations (oncology patients, pediatrics)



Inpatient settings often omit critical
threshold for high values

Platelet Count


>1,000 x

Threshold for low value commonly varies
across settings (inpatient vs. outpatient) and patient populations
(oncology patients, pediatrics)

Prothrombin Time

Not applicable

International Normalized Ratio (INR) >


Partial Thromboplastin Time

Not applicable

>100 seconds

High value may have higher threshold (eg,
>120 seconds) or may be specified relative to the normal range
(eg, >3 times upper limit of normal)

Blood Culture

Not applicable

Positive result


Cerebrospinal Fluid Culture or Direct

Not applicable

Positive result


Acid Fast Bacilli Stain (any

Not applicable

Positive result


Cryptococcal Antigen (serum or
cerebrospinal fluid)

Not applicable

Positive result


A typical policy for the appropriate response to
a critical value is that someone from the laboratory must notify by
telephone a physician, nurse, physician assistant, or medical
assistant at the ordering location. In accordance with JCAHO
requirements, laboratory staff must ask the recipient of the
results to read-back the results to ensure that the results were
properly received.

Critical values can vary depending on the needs
of patient population being served. Moreover, the specified
downstream responses may vary. A protocol in the clinical area
involved may direct the recipient of the call to place an alert in
the patient's chart (eg, a bright sticker with the lab value and
time called to the floor) and/or that a physician be contacted if
the recipient is a medical assistant or nurse.