with whom HARGRAVE, Chief Justice, joins, dissenting.
The court holds that the Workers’ Compensation Court’s order denying this claim must be vacated because the employer's medical expert, who found the claimant to be free of respiratory impairment, failed to comply with the American Medical Association’s “Guides to the Evaluation of Permanent Impairment” 1 [Guides]. I cannot accede to this part of today’s pronouncement for the following reasons: (1) this claim was denied for absence of a work-related. ;pulmonary injury — a fact found by the trial tribunal, which claimant does not dispute and (2) even if I were to assume the claimed disability to have been job-related, it is my firm view that the employer’s medical expert did not deviate from the Guides. Neither can I agree with today’s legal assessment of the claimant’s medical opinion. In my view, the court errs in gauging the probative value of that opinion by applying pre-Evidence Code norms of yesteryear’s Oklahoma common law, now abrogated.
I concur in that part of today’s opinion which announces a departure from the Per-linger 2 “jackpot rule.”3 Whenever an appellate court should conclude in the future that the employer’s or the claimant’s medical evidence is fatally flawed, no longer will the trial tribunal be directed to enter, on remand, an award based upon competent evidence of the opponent. I welcome and espouse this change.
I.
THE EMPLOYER’S MEDICAL REPORT SUPPORTS THE TRIAL TRIBUNAL’S ORDER DENYING THIS CLAIM
The claimant seeks permanent partial disability compensation for respiratory impairment sustained while on the job for this employer. The trial judge considered three medical letter-reports — the claimant’s, the employer’s and the independent examiner’s. The claimant’s physician, having found his lungs to be impaired as a result of continuous exposure to fuels and other chemicals, rated his disability at 50%. The court-appointed expert evaluated the condition at 20%. The employer’s medical expert attributed no impairment to the workplace and concluded “[a]ny symptoms [of respiratory disease] he does have ... are due entirely to 22 years of heavy smoking, although he has quit the last three years.”
The trial judge found the claimant “did not sustain an accidental personal injury arising out of and in the course of claimant’s employment with the above named respondent [the employer].” A three-judge panel affirmed the order denying the claim. The Court of Appeals vacated the compensation court’s decision, concluding “there is no competent evidence to support the finding of the trial court.” Citing Perlinger v. J.C. Rogers Construction Company,4 the appellate court remanded the claim, implic*1083itly directing that an award be made based on “the only competent evidence” — i.e., the reports of the claimant’s and court-appointed medical experts.
On review, claimant’s brief-in-chief attacked only the employer’s medical expert’s method of evaluating respiratory impairment. For corrective relief claimant relied solely on the contention that his zero impairment rating by the employer’s doctor stems from an unexplained deviation from the Guides. He did not question the physician’s primary conclusion and the trial tribunal’s critical finding that there is no job-related injury to be compensated. This alone makes a discussion of a claimed deviation from the Guides purely academic and dehors the scope of issues tendered for review. For purposes of workers’ compensation an assessment of permanent disability presupposes the existence of some on-the-job injury. Because the employer’s medical evidence supports the trial tribunal’s finding that the claimant’s injuries do not result from harm incurred in and about the working environment, I would sustain the order denying this claim.
II.
EVEN IF THE CLAIMANT DID SUFFER AN ON-THE-JOB INJURY, THE EMPLOYER’S MEDICAL REPORT IS NOT WITHOUT PROBATIVE VALUE
Assuming the dispositive question were, as the claimant urged on review, whether the employer’s medical expert improperly deviated from the Guides, the answer would favor the employer. Today, the court holds that the results of three breathing measures—forced vital capacity (FVC), forced expiratory volume (FEVi) and their ratio as percent (FEVi/FVC)—must be within the lower limits of normal to make a zero impairment rating conformable to the Guides.5 In this approach the court seems to depart from the teachings of Whitener v. South Central Solid Waste Authority,6 where we held that a respiratory “impairment rating may be rested on the results of but one” of the three ventila-tory function tests. In any event, the order denying this claim must still be sustained because not only were all three measurements correctly made by the employer’s physician, but also the results of each are within the normal range and hence support the doctor’s view as to the absence of respiratory impairment. See the attachment to this dissent, which shows the correctness of supporting calculations and findings.
The claimant argues, in essence, that the zero impairment rating given by the employer’s physician is based on a miscalculation. This alleged error is said to constitute an unexplained, and hence impermissible, deviation from the Guides. The claimant is clearly wrong. The employer’s evaluation is accurate because his medical expert made the necessary mathematical adjustment for this claimant’s race. Counsel for the claimant apparently overlooked this requirement. For a detailed explanation, see the attachment to this dissent.
*1084III.
A MEDICAL REPORT’S PROBATIVE VALUE MAY BE ADVERSELY AFFECTED BY THE EXPERT’S FAILURE TO ASSUME A COMPLETE AND ACCURATE HISTORY ONLY THROUGH CROSS-EXAMINATION YIELDING A CONTRARY OPINION OR DISCLOSING THE EXPERT’S INTENT TO ABANDON HIS ORIGINAL OPINION
The court concludes the claimant’s medical report lacks probative value because the physician relied upon an inaccurate or incomplete history when he attributed to the employee a 50% disability rating. At the hearing the employer challenged the report’s probative value for this very reason. Today the court views the medical opinion as utterly devoid of probative value after no more than comparing the history noted in the report with “other testimony or evidence."
Flaws relating to history arise in two contexts: when an expert’s opinion rests on some false assumption or when it is tainted by incomplete facts. Discrepancies may be initially apparent from a facial examination of competing medical letter-reports or they may escape discovery until some point in the course of an evidentiary hearing. At common law, the probative value of an expert’s opinion stood destroyed upon mere showing that the expert relied upon inaccurate or incomplete facts material to the professional’s assessment.7 This approach is no longer valid in light of the changes effected by the Code provisions. See 12 O.S.1981 §§ 2703 and 2705.8 Today it is the cross-examiner who has the burden of showing, through cross-examination, the expert’s failure to assume a complete or accurate history and of adversely affecting the opinion’s probative value by eliciting either a contrary opinion or the expert’s intent to abandon his original view based on the facts conformable to the proof in the record.9
Assuming the probative-value status of the claimant’s medical report were now in question on certiorari, I would hold generally that when the factual basis of an expert opinion is challenged for assumption of false or incomplete facts, the party against whom the evidence is offered has the burden of showing, through cross-ex-*1085animation, that the opinion would have been different had all the material and correct facts been assumed. If a medical opinion rests on a facially flawed history, that is, one in which factual inaccuracies or deficiencies are discoverable before hearing on mere visual inspection, then an objection to its competency (admissibility) should be filed and the expert’s deposition taken to ferret out the underlying facts. Should a discrepancy develop or initially appear at a hearing of the claim, the party against whom the opinion is offered should be given, upon request, an opportunity adversely to affect the opinion’s probative value through cross-examination of the expert.
In sum, the common law divined a fatal flaw from a materially tainted hypothetical question, while the Code treats an opinion based on differing or less comprehensive data as only challengeable, but not per se utterly devoid of probative force.10 Medical opinions now stand as prima facie probative, at least until their evidentiary value has been adversely affected through cross-examination that elicits from the expert either an opinion contrary to that originally given or his intent to abandon his first opinion.11
IV.
CONCLUSION
The employer’s medical report is not fatally flawed. It competently supports this claim’s denial. Because the “onus of eliciting the bases of the [claimant’s expert’s] opinion” clearly is cast by the Evidence Code upon the party against whom the report is offered {here, the employer),12 the court’s pronouncement today wrongly places on the claimant, who was the offering party, the burden of producing a letter-report in which all material data assumed are in strict conformity to the facts developed by the evidence.
I would hence vacate the Court of Appeals’ opinion and reinstate the trial tribunal’s order denying compensation.
ATTACHMENT
UNDISPUTED RAW DATA FROM THE EMPLOYER’S MEDICAL REPORT: Claimant is a black male:
Age: 46 year old ■
Weight: 186 lbs.
Height: 5'8" = 173 cm (68 in. x 2.54 cm/in. = 172.72 cm)
OBSERVED PULMONARY FUNCTION (SPIROMETRY RESULTS):
Forced vital capacity == FVC = 3.50 liters (1.)
Forced expiratory volume = FEVi = 3.11 1.
Ratio as percent = FEVi/FVC = 89% (3.11/3.50) X 100
PREDICTED NORMAL VALUES DERIVED FROM TABLES USING RAW DATA:
*1086FVC = 4.75 1. (Table 2, AMA Guides, 2d ed., at 89)
FEVi = 3.85 1. (Table 4, at 91)
FEVi/FVC = 81.0% (Table 6, at 93)
The lower limit of normal for FVC is the table-derived value for FVC minus the 95% Confidence Interval or 4.75 — 1.12 = 3.63 1.
The lower limit of normal for FEVi is the table-derived value for FEVi minus the 95% Confidence Interval or 3.85 — 0.842 = 3.01 1.
The lower limit of normal for FEVi/FVC is the table-derived value for FEVi/FVC minus the 95% Confidence Interval or 81.0% — 8.28 = 72.7%.
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“The spirometry results for black patients should be divided by 0.9 before they are compared to the predicted values.” AMA Guides, 2d ed., at 89.
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CLAIMANT’S ADJUSTED SPIROMETRY RESULTS:
FVC = 3.89 1. (3.50 1./0.9)
FEVi = 346 1. (3.11 1./0.9)
FEVi/FVC = 89% (3.46/3.89) X 100
CONCLUSION:
The claimant’s ventilatory function test results are all within the normal range:
Claimant’s values Lower limit of normal
FVC 3.89 1. 3.63 1.
FEVi 3.46 1. 3.01 1.
FEVi/FVC 89% 72.7%
. Although the third (1988) edition of the AMA Guides has been published, the claimant concedes, and the court recognizes, that the 1984 version applies to this claim.
. Perlinger v. J.C. Rogers Const. Co., Okl., 753 P.2d 905, 907 (1988).
. See LaBarge v. Zebco, Okl., 769 P.2d 125, 130-131 (1989) (Opala, J., concurring in part and dissenting in part); Perlinger v. J.C. Rogers Const. Co., supra note 2 at 907 (Opala, J., concurring in part and dissenting in part).
. See supra note 2.
. The court’s opinion lists "three tests ... required to confirm that an examinee fits ... [the 0% impairment] category.” They appear to include: 1) dypsnea (shortness of breath), 2) ven-tilatory function (FVC, FEVi, FEVi/FVC) and 3) "oxygen consumption per minute” or measured exercise capacity (VO2 Max). Because neither the 1984 nor the 1988 version of the Guides requires normal results from all these measurements as a precondition to a finding of no impairment, I assume the three required tests to which the court refers are those of ventilato-ry function alone.
Although the 1984 version of the Guides governs this claim (see supra note 1), the 1988 edition does contain a noteworthy change. It provides that the ”[r]esults for all four measures of lung function must be in the normal range for a person to be considered not impaired according to physiologic parameters.” (Emphasis added.) Three of those four tests are for ventilatory function (FVC, FEVi and FEVi/FVC ratio). The fourth measurement is the diffusing capacity of carbon monoxide, Dco. While the latter test is not pertinent to a zero impairment classification, according to the 1984 Guides, both the 1984 and 1988 editions allow the "measured exercise capacity” test alone (VO2 Max) to be used as an alternative basis for placing the ex-aminee in the 0% impairment category.
. Okl., 773 P.2d 1248, 1251 (1989).
. See Glaspey v. Dickerson, Okl., 350 P.2d 939, 942 (1960).
. The terms of 12 O.S.1981 § 2703 provide:
"The facts or data in the particular case upon which an expert bases an opinion or inference may be those perceived by or made known to him at or before the hearing. If of a type reasonably relied upon by experts in the particular field in forming opinions or inferences upon the subject, the facts or data need not be admissible in evidence." (Emphasis added.)
The terms of 12 O.S.1981 § 2705 provide:
"The expert may testify in terms of opinion or inference and give his reasons therefor without prior disclosure of the underlying facts or data, unless the court requires otherwise. The expert may be required to disclose the underlying facts or data on cross-examination.” (Emphasis added.)
Since "an expert may testify in the form of an opinion without prior disclosure of the underlying facts or data,” a discrepancy between facts adduced in evidence and those shown to have been assumed by the expert does not by itself operate to sap or destroy the opinion's probative value. See Tiedemann v. Radiation Therapy Consultants, 299 Or. 238, 701 P.2d 440, 444 (1985) and Bostick Tank Truck Service v. Nix, infra note 9 at 1348; see also 1 Whinery, Oklahoma Evidence, § 2705 at 255 (1985) ("Section 2705 complements Section 2703 and does not require, but permits, the direct examiner to bring out the underlying data upon which the expert’s opinion is based, if it is appropriate and does not confuse the trier of fact or require undue time consumption” (Emphasis added.)); Blakey, An Introduction to the Oklahoma Evidence Code: the Thirty-fourth Hearsay Exception, 16 Tulsa L.J. 1, 5, 8 (1980); Jackman and Gilsinger, Expert Testimony Under the Oklahoma Evidence Code, 61 O.B.J. 767, 774-775 (1990).
.Bostick Tank Truck Service v. Nix, Okl., 764 P.2d 1344, 1348 (1988). See also Smith v. Ford Motor Co., 626 F.2d 784, 793-794 (10th Cir.1980), cert. den. 450 U.S. 918, 101 S.Ct. 1363, 67 L.Ed.2d 344 (the combined effect of Rules 703 and 705, Federal Rules of Evidence, [or 12 O.S.1981 §§ 2703 and 2705, supra note 8] is to place the burden of exploring the facts and assumptions underlying the expert’s opinion squarely on the shoulders of opposing counsel in cross-examination); Bryan v. John Bean Division of FMC Corp., 566 F.2d 541, 545 (5th Cir.1978) ('“the onus of eliciting the bases of the opinion is placed on the cross-examined' (Emphasis added.)).
. An expert's opinion which may be deemed utterly devoid of probative value for a facially apparent fatal departure from the Guides must be distinguished from one that is vulnerable to destruction by cross-examination because of discrepancies in or of incomplete facts assumed by the expert. In the former instance, the question presented is one of law, LaBarge v. Zebco, supra note 3 at 127, while in the latter instance, it is one of credibility and hence beyond the reach of a reviewing court’s scrutiny. See Peabody Galion Corp. v. Workman, Okl., 643 P.2d 312, 314-315 (1982).
. When facts at variance with those assumed in a physician’s medical letter-report or deposition are revealed, it devolves upon the party opposing the proof to challenge the probative value of the opinion for assumption of an inaccurate or incomplete history or for want of some critical fact. If the trial judge should not sustain the challenge, the party against whom the opinion is offered must be afforded, upon request, an opportunity to show, through cross-examination, that the expert's opinion would be different or abandoned if the complete or correct facts were known. Should the trial judge rule against the offering party, the latter must be afforded the opportunity either to stand on the opinion or to replace it. This practice in the Workers’ Compensation Court seems to be required by the Evidence Code’s provisions that abolish the common law’s hypothetical question device. See Bostick Tank Truck Service v. Nix, supra note 9 at 1348; Whitener v. South Cent. Solid Waste Auth., supra note 6 at 1249 n. 2; see also Bryan v. John Bean Division of FMC Corp., supra note 9 at 545.
.See the authorities cited supra note 9.