Pathology/Lab Coding Alert

With the threat of bioterrorism becoming a reality, clinicians are often the first line of defense in identifying potential cases of anthrax. As part of both the diagnostic and epidemiological network, pathologists and laboratories are being called on to conduct specific tests to help identify this once-uncommon organism.
 
Anthrax Microbiological Testing

Identifying anthrax from nasal swabs has been widely reported recently. "It is important to realize that the nasal swabs are an epidemiological tool, not a diagnostic test for anthrax," says Ray Kaplan, PhD, clinical scientist for microbiology and serology at Quest Diagnostics Inc. in Atlanta. "Along with environmental testing, the swabs are used to analyze the extent of exposure to a population. If positive, a nasal swab does not indicate that an individual is infected with the disease, but has been exposed to it."
 
Report a nasal swab culture provided to screen for anthrax as CPT 87081 (culture, presumptive, pathogenic organisms, screening only).
 
Rapid field tests for Bacillus anthracis, such as the antibody-based Guardian BTA test strips, are also used for investigative rather than diagnostic purposes. "None of these products are FDA-approved and, to my knowledge, a published assessment of their accuracy is not available," Kaplan says.

Culture
 
For patients with clinical symptoms of anthrax, growing a culture of Bacillus anthracis is the most straightforward and certain method to confirm infection. Depending on the symptoms and apparent route of infection, the culture may be taken from many sources such as blood, tissue biopsy, skin lesion exudate, sputum or cerebrospinal fluid (CSF).
 
"Bacillus anthracis is readily cultured on standard blood agar plates, and colonies may be evident as early as six to eight hours, or nearly always within 18 to 24 hours, depending on the original bacterial concentration and contamination level," Kaplan says. These cultures are reported based on the source: 87040 (culture, bacterial; blood, with isolation and presumptive identification of isolates [includes anaerobic culture, if appropriate]) or 87070 (... culture, bacterial; any other source except urine, blood or stool, with isolation and presumptive identification of isolates).
 
"Beyond the culture morphology, growth on selective media and Gram stain, if a biochemical panel is run to perform a definitive identification, also report 87077 (... culture, bacterial; aerobic isolate, additional methods required for definitive identification, each isolate)," says William Dettwyler, MT-AMT, coding analyst for Health Systems Concepts, laboratory coding and compliance consultants in Longwood, Fla. CPT defines definitive identification as "identification to the genus or species level that requires additional tests (e.g., biochemical panels, slide cultures)."
 
"Identification involves several tests that point strongly to B. anthracis but do not rule out a few related Bacillus strains," Kaplan says. "Any isolate that is Gram-positive, aerobic, nonmotile, nonhemolytic and nonurease active would be highly suspicious. Labs are required to send any such isolate to the appropriate state public-health laboratory for further testing."
 
Certain state reference labs are part of the Laboratory Response Network for Bioterrorism and, as such, have access to protocols and reagents from the Centers for Disease Control and Prevention (CDC) for testing agents such as anthrax. The CDC has established a locator system for these labs that is available on the Internet at www.cdc.gov.
 
Elizabeth Franko, DrPH, director of the Georgia Public Health Laboratory in Atlanta, says her lab carries out the microbiology tests for definitive identification of B. anthracis. "We carry out the gamma phage test, which subjects the culture to a virus that specifically 'cuts up' B. anthracis and causes a clearing of cells on the plate," Franko says. Although the public-health laboratories do not report these services to insurance for reimbursement using CPT codes, the procedure described by this test is 87158 (culture, typing; other methods).
 
"We also provide two direct fluorescent antibody (DFA) tests, which attach to and 'stain' different portions of the B. anthracis antigen coating," Franko says. These are the capsular staining test, which identifies the capsule (protective shell) for B. anthracis, and the polysaccharide staining test, which illuminates the distinctive sugar found on the outside of B. anthracis. Although not reported to insurance, the code that describes these tests is 87140 (culture, typing; immunofluorescent method, each antiserum).
 
"Confirmation of B. anthracis culture depends on the original presumptive identification as well as positive results on specific combinations of all of the tests we conduct," Franko says. This would be a positive gamma phage plus a positive capsule DFA and positive results on the polysaccharide DFA test.

Nonculture Tests
 
Other than cultures, specimens such as tissue biopsy or direct smears from various sources, e.g., lesion exudate, blood, CSF, respiratory secretions, may be evaluated for anthrax. "Direct smears will be less reliable than cultures because the organism may be present in low numbers or in the spore form, which does not stain readily," Kaplan says.  

Gram stain and evaluation of direct smear is reported as 87205 (smear, primary source with interpretation; Gram or Giemsa stain for bacteria, fungi, or cell types). Biopsy of tissue such as a cutaneous lesion (e.g., 88305 level IV - surgical pathology, gross and microscopic examination, skin, other than cyst/tag/debridement/plastic repair) may indicate the presence of anthrax through the use of special pathology stains, e.g., 88312, special stains ... group I for microorganisms ... each.
 
Although less common, laboratory analyses are available for the identification of B. anthracis from sources other than culture. Most of these tests are not commercially available or FDA-approved and are carried out only at certain public-health laboratories and the CDC. These tests, along with the code that describes the procedure, are as follows:
 

Polymerase chain reaction (PCR) This test compares known genetic sequences of B. anthracis to the antigen being identified, from various sources. "The code for this test is 87798 (infectious agent detection by nucleic acid [DNA or RNA], not otherwise specified; amplified probe technique, each organism)," Dettwyler says.
 

Immunohistochemistry This test identifies the specific antigen, B. anthracis, in tissue, through the use of antibody enzyme markers. "The procedure is described by 88342 (immunocytochemistry [including tissue immunoperoxidase], each antibody)," Dettwyler says.
 

Antibody test Carried out on blood samples, this test uses enzyme-linked immunosorbent assay (ELISA) for antibody detection. The test is described by 86609 (antibody; bacterium, not elsewhere specified). "Because this test identifies antibodies that develop 10 to 14 days after infection, which is too late for diagnostic and treatment purposes, it is used primarily as an epidemiological tool," Kaplan says. This serology test is conducted at the CDC.

The CDC has provided specific epidemiological and clinical definitions for anthrax cases. A confirmed case is considered to be a patient with clinical symptoms of anthrax and confirmation through isolation of B. anthracis culture or two supporting nonculture tests, i.e., immunohistochemistry, PCR, serology. A suspected case is defined as a patient with clinical symptoms without culture isolation, but with either one positive nonculture test or a link to exposure.
 
Both suspected and confirmed cases should be reported to state or local public-health authorities, who in turn coordinate with the CDC. The CDC uses these definitions to determine intervention strategies such as antibiotic prophylaxis.

A laboratory receives a skin biopsy specimen identified as "suspected anthrax." The pathologist conducts an evaluation, reported as 88305 (level IV-surgical pathology, gross and microscopic examination skin, other, than cyst/tag/debridement/plastic repair). This would be the appropriate code for a skin lesion evaluation, whether or not the final diagnosis is cutaneous anthrax.
 
Special stains for microorganisms may be carried out, and each is separately reported as 88312 (special stains [list separately in addition to code for surgical pathology examination]; group I for microorganisms [e.g., Gridley, acid fast, methenamine silver], each). Although not commonly available, an immunohistochemistry test may be carried out to identify specifically the presence of the Bacillus anthracis antigen in the tissue biopsy. This test is described by 88342 (immunocytochemistry [including tissue immunoperoxidase], each antibody).
 
If the tissue biopsy is cultured to rule out anthrax, report 87081 (culture, presumptive, pathogenic organisms, screening only). If a culture is grown, and the isolate presumptively identified, report 87070 (culture, bacterial; any other source except urine, blood or stool, with isolation and presumptive identification of isolates). Definitive identification to the genus level may require a biochemical panel, reported as 87077 (culture, bacterial; aerobic isolate, additional methods required for definitive identification, each isolate). Although testing to this level would not eliminate the possibility that the isolate is one of a few related Bacillus strains, any isolate that is Gram-positive, aerobic, nonmotile, nonhemolytic, and nonurease active would be highly suspicious for B. anthracis.
 
Positive identification as B. anthracis requires additional testing of the isolate. These tests are available at certain public-health laboratories, using CDC protocols and reagents. The tests include the gamma phage test and two direct fluorescent antibody (DFA) tests for the capsular and polysaccharide coatings distinctive to B. anthracis. The gamma phage test is described by 87158 (culture, typing; other methods), and each of the DFA tests is identified by 87140 (culture typing; immunofluorescent method, each antiserum).