Servces 
Department of Health and Human 

OFFICE OF

INSPECTOR GENERAL

ZERO CROSSERS

( JiL  Richard P. Kusserow 
INSPECTOR GENERA 
AUGUST 1991
,f3a  OFFCE OF INSPECfORGENRA

The mission of the Offce of Inspector General (OIG), as mandated by Public Law 95-452 
as amended, is to protect the integrty of the Department of Health and Human Servce 
(HHS) programs as well as the health and welf!ire of beneficiaries served by those programs.
Th 
statutory mission is carried out through a natiOfwi  e network of audits, investigations 
, and inspetions conducted by three OIG operating 'components: the Offce of Audit 
Servce, the Office of Investigations, amI the Offce of Evaluation and Inpections. The 
DIG also inform the Secretary of HHS of program and management problems and 
recmmends courses to correct them. 
OFFCE OF AUDIT SERVICE 
The DIG's Offce of Audit Servces (OAS) provides all auditing servce for HHS, either by 
conducting audits with its own audit resurce or by overseeing audit work done by others. 
Audits examine the performance of HHS programs and/or itS grantees and contractors in 
carrng out their respective responsibilities and are intended to provide independent 
asesments of HHS programs and operations in order to reduce waste, abuse, and 
mimanagement and to promote economy and effciency throughout the Department. 
INTIGATIONS 
OFFICE OF 
The DIG's Offce of Investigations (01) conducts criminal, civil, and administrative 
investigations of allegations of wrongdoing in HHS programs or to HHS beneficiaries and of 
unjust enrchment by providers. The investigative effort of 01 lead to crinal convictions 
, or civil money penalties. The 01 also oversee State Medicaid fraud 
admintrative sanctions
control units which investigate and prosecute fraud and patient abuse in the Medicaid 
program. 
AN 
OFFCE OF EVALUATION  INSPECTONS 
The DIG's Office of Evaluation and Inpections (DEI) conducts short-term management and 
progrm evaluations (called inspections) that focus on isues of Concern to the Department 
the Congress, and the public. The' findings and recommendations contained in these 
inpetion report generate rapid, accurate, and up-to-ate information on the effciency, 
wlnerabilty, and effectiveness of departmental programs. 
The report was prepared by the Philadelphia Regional office under the direction of 
Joy Quil, Regional Inspector General and Robert Vito, Deputy Regional Inpector General. 
Project Staff: 
Robert A  Project Leader 
Katz, 
Cythia R. Hansford

W. Mark Krushat (Headquarters)

Wayne Powell (Headquarters)
 Department of Health and Human 
Services

OFFICE OF

INSPECTOR GENERA

ZERO CROSSERS

Richard P. Kusserow 
INSPECfOR GENERAL 
'.t 
Ciao  OEI-03-91 EXECUTIVE 
SUMMAR 

PUROSE 
This report quantifies Medicare reimbursement for in-office diagnostic tests of
arteries and veins conducted with ultrasonic detecting 
devices using a "zero-crossing
technique. 
BACKGROUN 
In a previous report (Low-Cost U1trasound Equipment, OEI-03-88-01401), we
reviewed the appropriateness of Medicare reimbursement for 
diagnostic tests
conducted with unsophisticated, ultrasonic devices. We encountered two basic tyes
of devices-- Pocket Dopplers and Zero Crossers. 
Pocket Dopplers are the least sophisticated tye of ultrasound equipment. Small 
hand-held devices, they are tyically nondirectional and their only output is audio. 
A variety of devices exist at a technological step above Pocket Dopplers. 
These 
devices--which we term Zero Crossers--document test results via a recordable 
waveform, similar to an electrocardiograph (EKG) record. 
Typically, these devices 
are bidirectional, constructed in a table-top configuration, and cost between $3000 
and $7000.

METHODOLOGY 
This report is based on a random sample consisting of 480 services from 8 Medicare 
carriers. The selected carriers represent more than half of in-office allowances for 
ultrasonic vascular tests nationally. We limited the selected servces to 
in-office 
diagnostic vascular tests conducted during 
1988. 
FININGS 
Seventeen Percent of Servces Were Conducted Wih Zero 
Crossers 
Fifty-
three servces in our  ample--represeI)ting 17 percent of the responses--were 
conducted with Zero Crossers. We calculate that Zero Crossers were used to 
conduct 62 079 servces in 1988.  Medicare Allowed Between  $8  and  $12  Million for Servces Conducted With Zero

Crossers in 1988

We estimate that Medicare allowed about $8 milion for servces 
conducted with 
Zero Crossers. If non-respondents and respondents had the same usage rate
, an
additional $4 milion 
could have been allowed for Zero Crossers in 1988. 
Zero Crosers May Be Inaccuate 
Many Tests Done  Wtth 
A review of scientific literature revealed a number of studies 
highlighting deficiencies
in the accuracy of equipment 
using zero-crossing technology. 
Reimburement for Zero Crossers and More Sophisticated  Simil 
Eqipment are 
Zero Crossers were reimbursed about the same as 
devices producing sophisticated
and clinically detailed imaging. The Medicare allowance for Zero Crossers was 
approximately $125 (weighted average) while the average allowance for state-of-the
art equipment was about 
$135. 
CONCLUSION 
Our "Low-Cost Ultrasound Equipment" report recommends that HCF A advocate 
revisions in procedure codes and reimbursement rates to reflect the 
different levels 
of sophistication and quality of diagnostic information provided in such tests. 
\Ve continue to support this recommendation. If HCF A adopts it, potential savings
from the 5-year period beginning 1992 range from about $25 million to 
$124 millon 
depending on the reimbursement level.  . . ..  ..  ...   ...   ...   ...   ...   ...   ...   ...   ...   ...   ...   ...   ...   ...   ...   ...   ...   ...   ...   ...   ...   ...   ...   ...   ...   ...   ...   ...   ...   ...   ...   ..  ..  . . 
TABLE OF 
CONTENTS

EXUT SUMY

INODUCTON 
. . . . . . . . . . . I

FIINGS 
................................................... 5

CONCLUSION  . . . . . . . . . . . . . 7

APPENIX 
. . . . . . . . . . . . . A INTRODUCTION

PUROSE 
This report quantifies Medicare reimbursement for in-office diagnostic tests of
arteries and veins conducted with ultrasonic 
detecting devices using a "zero-crossing
technique. 
BACKGROUN 
Diagnosticians use sensitive instruments operating on ultrasound principles to 
detect
arterial and vascular diseases. These devices emit high frequency soundwaves into 
the tissues. Depending on the sophistication of the device used, reflected ultrasound
signals may be detected by one of four techniques--audio only, strip-chart recording 
using a "zero crossing" technique, spectral analysis, or imaging. In general, audio-
only devices are considered the least accurate and refined of the various methods.

Imaging devices produce superior 
diagnostic output.

Diagnostic ultrasound tests are usually conducted using "mid-level" equipment. This
equipment costs from $15 000 to $60 000 and offers a wide range of sophisticated
options, such as remote control, selectable frequency ranges, and video spectrum
analysis of blood flow measurements. The ensuing diagnostic output provides a level 
of quality which meets the needs of most 
clinicians. 
More expensive (so-called "state-of-the-art ) equipment offers two-dimensional 
displays, computerized analysis, and color-flow imaging. Devices equipped with 
color-flow imaging produce video pictures of blood flow velocities in combinations of 
red, blue, and green. Changes in the intensity of color and blood flow velocity can
indicate an irregularity, such as a blockage. 
Nationally, Medicare allowances for four major procedure codes 
used in diagnostic
ultrasound tests of arteries and veins surpassed $88 million for in-office servces in 
1989, an increase of more than 31 percent over 1988. These tests increased almost 
25 percent for the corresponding period.

In a previous report (Low,.Cost Ultrasound Equipment, OEI-03-88-01401), we
reviewed the appropriateness of Medicare 
reimbursements for diagnostic tests
conducted with inexpensive. relatively unsophisticated ultrasonic devices. We 
encountered two basic 
types of devices--Pocket Dopplers and Zero Crossers.  Zero Crossers 
Pocket Dopplers  and 
Pocket Dopplers are the least sophisticated type of ultrasound equipment. A hand
held device, the typical Pocket Doppler transmits a continuous or pulsed beam of 
ultrasound at moving blood cells. Typically, the Pocket Doppler is non directional 
(i.  , it is incapable of determining the direction of blood flow) and produces audio 
signals only. Such tests can be conducted in less than five minutes. These 
devices 
are marketed as diagnostic ultrasound equipment and generally cost under 
$1000. 
We reported the impact of Pocket Doppler usage in a Management Advisory 
Report, entitled "Pocket Dopplers" (OEI-03-91-00461). Our findings on Zero
Crossers are addressed in this report. 
A variety of devices exist at a technological step above Pocket Dopplers. 
These 
devices--which we term Zero Crossers--document test results via a recordable 
waveform. This process converts the mean frequency of the doppler 
signal into a 
proportional display via a frequency-to-voltage (zero crossing) strip-chart tracing, 
similar to an electrocardiograph (EKG) recording. Typically, these devices are 
bidirectional (capable of determining blood flow direction), constructed in a table
top configuration, and cost between $3000 and $7000. 
Test result evidence is the most obvious clinical difference between Pocket Dopplers 
and Zero Crossers. (Pocket Dopplers do not produce objective test evidence while 
Zero Crossers provide 
tangible evidence.) More sophisticated equipment provides 
detailed documentation using spectral analysis or high-resolution images. 
A device using zero-crossing technology records the average speed of all the cars on 
a highway, while spectral analysis registers the individual speed of each car
, according 
to an analogy offered by one expert. In effect, a Zero Crosser provides a single 
frequency display of the soundwave whereas spectral analysis records multiple 
quantitative frequencies. State-of-the-art equipment tyically 
produces test results in 
a video hard-copy image.

Approximately 15 manufacturers produce and market Pocket Dopplers and Zero 
Crossers. Industry sources estimate that at least 100 000 units are in active use in 
the medical community. About 20 000 new units were sold in 1990.  Prevous Inspection Finings 
Our previous study highlighted a number of issues and concerns. Briefly, we found: 
A variety of ultrasound equipment exists ranging from Pocket Dopplers to 
state-of-the art equipment costing more than $300 
000. 
Medicare procedure codes fail to distinguish between test tyes or results. 
The Health Care Financing Administration Procedure Coding System
(HCPCS) does not differentiate between the extent of a test or the nature 
test results. Further, the same rate of reimbursement applies to a test
without regard to its 
extensiveness or the quality of the data produced. 
There are strong incentives for excessive use. Since Medicare 
reimbursements do not consider the quality of equipment used and the 
quality of test results, excessive payments can be claimed for a relatively
simple screening test based on a comparatively modest investment. 
The Health Care Financing Administration (HCF A) is vulnerable to 
inappropriate bilings. Medicare carriers lack sufficient safeguards to detect
bilings based on inferior test results. 
A precedent exists to deny payments for Pocket Doppler tests. 
In a previous 
decision, HCF A ruled that a portable hand-held x-ray instrument "should be 
reimbursed as part of the physician s professional service, and no additional 
charge should be allowed. 
We recommended that HCFA prohibit payment for Pocket Doppler tests and 
advocate revisions in procedure codes and reimbursement rates to reflect the 
different levels of sophistication and quality of diagnostic information provided in 
ultrasound tests. 
METIODOLOGY 
This report is based on a 2-stage random sample consisting of 480 servces from 8 
Medicare carriers. During the first stage of sampling, 8 Medicare carriers were 
randomly selected, with the probability of selection proportionate to total amounts 
reimbursed under Medicare in 1988. The selected carriers represent more than half 
of in-office allowances for ultrasonic vascular tests nationally. The carriers were 
Florida Blue Shield; Michigan Blue Shield; Empire Blue Shield (New York);
California Blue Shield; Arkansas Blue Shield, as the carrier for Louisiana; Blue 
Shield of Indiana; Transamerica Occidental of California; and the Railroad 
Retirement Board.
 At the second stage of sampling, we selected 60 servces per carrier from 1988 Part 
B Medicare Annual Data (BMA) bilings. We limited the selected services to in-
office diagnostic vascular tests conducted during 1988. The services consist of four of 
the most commonly used HCPCS codes by practitioners of these tests: 93910 
(noninvasive studies of lower extremity arteries); 93950 (noninvasive studies of lower 
extremity veins); 93860 (noninvasive studies of carotid arteries); 
and 93890 
(noninvasive studies of upper extremity arteries). 
After the carriers supplied us with pertinent claims data, we wrote to the 
practitioners requesting detailed information on the 
tyes of equipment used
conduct the tests. In particular, we were interested in five features--configuration 
(pocket, portable, pen, tabletop); power source; blood flow direction; price; and 
documentation capabilty. We also requested copies of any charts, graphs, or 
printouts produced during the tests. 
We reviewed the responses against scientific publications, manufacturers' catalogs 
and related technical materials to determine if low-cost devices had been used to 
conduct the tests. We consulted with a Registered Vascular Technologist (RVT) 
who reviewed test results and assisted us in making determinations.  FINDINGS

Seventeen Percent of Servces Were Conducted With Zero Crossers 
Sixty-five percent of the providers in our sample (314 of 480) responded to our 
requests. Based on our analysis, we determined that 53 services in our sample-
representing 17 percent of the responses--were conducted with Zero Crossers. 
Applying the 17 percent usage rate and the 65 percent response rate, we calculate 
Zero Crossers were used to conduct 62 079 services in 1988. If non-respondents 
usage rates were the same as for respondents, servces conducted by Zero Crossers 
could increase by 33 427 in 1988, bringing total 1988 servces to 95 506. 
In our "Pocket Doppler" report, we found that Pocket Dopplers accounted for 7 
percent of ultrasound tests in 1988. Taken together, tests done by Pocket Dopplers
and Zero 
Crossers represent nearly one-quarter of all in-office ultrasound tests 
conducted in 1988. 
Medicae Alowed Between $8 and $12 Mion for Servces Conducted With Zero 
Crossers in 1988. Alowances for 5 Years  Mion 
Could be $124 
Allowances for sample servces conducted with Zero Crossers ranged from a low of 
$15 to a high of $324 with an overall weighted average of $125. Based on our 
projections, we estimate that Medicare allowed approximately $8 millon for these 
services. If we assume that non-respondents and respondents had the same usage 
rate, an additional $4 milion 
could have been allowed for Zero Crossers in 1988. 
\Ve estimate that Medicare will allow 
approximately $124 milion for services 
conducted with Zero Crossers for the 5-year period beginning in 1992. To estimate 
Medicare allowances, we applied the 
65 percent response rate and the 17 percent 
Zero Crosser usage rate to the 700 
700 allowed services for the 4 codes in 1989. 
Non-respondents were not included in our calculations even though there is no 
reason to suspect the usage rate for non-respondents differs from respondents. 
assumed an annual 20 percent increase in the number of servces (the actual annual 
increase from 1987 to 1989 was between 25 and 30 percent). We used the 1988 
average allowed amount of $125 per service for all 5 years. We omitted possible
reimbursement increases because of recent legislative 
changes designed to minimize 
ITcreases. 
Many Tests Done With Zero Crossers May Be Inaccurate 
Deficiencies in the accuracy of equipment using zero-crossing applications have been 
recognized for many years. 
1988 study of 157 patients concluded:  ...... , " , "
the errors...of zero-crossing techniques have been recognized for 
10 to 15 
years...The inability of the zero-crossing tracing to provide complete and 
accurate information in 50 percent of the cases severely limits its 
usefulness. ' 'I 
A 1977 study on multiple arterial readings concluded: 
recordings made by zero-crossing detectors cannot be used for quantitative 
analysis. Moreover, errors are common enough that even qualitative 
interpretation of the recordings may be questionable in many cases. 
Additional pertinent references are. cited in the Appendix. 
Our consultant who examined a sample of test results confirmed that Zero Crossers 
often produce questionable results compared with more sophisticated equipment. 
Reimburements for Zero Crossers and More Sophiticated Equipment are Simar 
The 53 devices we determined to be Zero Crossers were reimbursed about the same 
as devices producing sophisticated and clinically detailed imaging. Overall, the 
weighted Medicare average allowance for Zero Crossers was 
approximately $125 
while the average allowance for services conducted with more sophisticated 
equipment was $135. 
In theIr efforts to market Zero Crossers, manufacturers do not neglect the potential
compensation which their products provide. As an example, one of the brochures 
we encountered contained this advice: 
In addition to its diagnostic value, low cost and simplicity of operation

the annotated charts provide invaluable documentation in this age of

medical-legal liability. (Name of device) tests are MEDICARE approved 
and reimbursable by third party insurers under several CPT 
codes. Average 
reimbursement exceeds $150. 
1 Cynthia Kupper Burnham, RVT, Nancy Dewhirst, RVT, and Steven J. 
Burnham, MD  Doppler Spectral Waveforms For Recording Peripheral Arterial 
Signals: The Preferred Method  The Joumal of Vascular Technology,  April, 1989. 
2 K. Wayne Johnston
, MD, Bruno C. Maruzzo, MASc, and Richard 
S. C. 
Cobb aId, ARCS, MSc, PhD  Inaccuracies Of A Zero-Crossing Detector For 
Recording Doppler Signals  Surgcal Forum
, 1977.  CONCLUSION

Our report on Low-Cost Ultrasound Equipment recommends that HCF A advocate 
revisions in procedure codes and reimbursement rates to reflect the 
different levels 
of sophistication and quality of diagnostic information provided in such tests. (We 
understand HCF A has encouraged procedure code revisions in vascular tests during 
recent contacts with the American Medical Association s editorial board. 
We estimate the following potential savings on Zero Crosser servces if HCF A 
adopted our recommendation. The chart depicts various payment options ranging 
from non-coverage to $100 for I-year and 5-year periods. 
ZERO  CROSSERS

REIMBURSEMENT  YEAR SAVINGS  YEAR SAVINGS 
$16.  MILLION  $124. 5 MILLION 
$20  $14.  MILLION  $104. 5 MILLION 
$40  $11.4  MILLION  $84.  MILLION 
S60  $8. 7 MILLION  $64.  MILLION 
$80  $6, 0 MILLION  $44.  MILLION 
$100  $3. 3 MILLION  $24. 9 MILLION  , " , " , ", ," " , "
APPENDIX

REFERENCES 
Barnes, Robert W.  Noninvasive Diagnostic Techniques In Peripheral Vascular 
Disease  American Heart Joumal 
February, 1979. 
Flax , Webster , and Updike Noise And Functional Limitations Of 
, S.  , J.  , S. 
The Doppler Blood Flowmeter " Department of Electrical Engineering, Department 
of Medicine, University of Wisconsin, Madison, Wisconsin. 
Johnston, K. Wayne, Maruzzo, Bruno c., and Cobbold, Richard S.  Errors And 
Artifacts Of Doppler Flowmeters And Their Solution " Read Before The 25th 
Meeting Of The International Cardiovascular Society, Rochester, New York, June 16 
1977. 
Nix, M. Lee, and Barnes, Robert W.  Noninvasive Peripheral Vascular Laboratory 
Diagnostic Techniques " University of Arkansas For Medical Sciences, Little Rock 
Arkansas
, 1985. 
Reneman, Robert S., Clarke, Howard F., Simmons, Norman, and Spencer, Merrill P. 
In Vivo Comparison Of Electromagnetic And Doppler Flowmeters: With Special 
Attention To The Processing Of The Analogue Doppler Flow Signal  Cardiovascular 
Research
, 1973. 
Reneman, Robert S., and Hoeks, Arnold P.  Doppler Ultrasound In The 
Diagnosis Of Cerebrovascular Disease  Research Studies Press, 1982. 
Reneman, Robert S., and Spencer, Merril P.  Difficulties In Processing Of An 
Analogue Doppler Flow Signal; With Special Reference To Zero-Crossing Meters 
And Quantification " Janssen Research Foundation, Beerse, Belgium, and Institute of 
Environmental Medicine and Physiology, Seattle, Washington.