Opinion for the court by Senior Judge GALLAGHER.
Dissenting opinion by Chief Judge WAGNER at p. 8.
GALLAGHER, Senior Judge:Appellant commenced this medical malpractice suit alleging that the District of Columbia General Hospital’s negligence led to the amputation of the front half of his right foot. After a mistrial due to a hung jury, the District of Columbia (the “District”) filed a Motion for Entry of Judgment pursuant to Super.Ct.Civ.R. 50(b), claiming that appellant failed to prove the existence of a national standard of care and failed to show proximate cause. On July 19, 1993, the trial court granted the District’s motion and entered judgment in favor of the District. Appellant appeals the trial court’s ruling. We affirm.
I.
Appellant was treated at D.C. General Hospital for traumatic injuries resulting from an automobile accident. Doctors performed a splenectomy1 several days after the accident. After the splenectomy, appellant developed a blood clot above his right ankle which obstructed the flow of blood to his right foot. Gangrene developed in his foot *568and it was partially amputated. He later brought suit against the District for medical malpractice. In support, he alleged a failure to properly administer aspirin following the removal of his spleen permitted a blood clot to form in his ankle, causing gangrene and necessitating the amputation.
His claim of medical malpractice was based upon the contention that the failure of the hospital physician to give him aspirin after the operation when his blood platelet level reached 800,000 to 1,000,000 constituted negligence. This negligence, says appellant, caused the injury.
Plaintiff offered a medical expert witness to establish that aspirin should be administered to prevent a clot in a post-splenectomy patient; and that the surgeon who performed this operation on plaintiff breached the applicable standard. The specific issue being addressed was whether the surgeon had delayed too long in administering aspirin as an anti-platelet therapy, the purpose being to ward off the formation of blood clots. While aspirin was in fact administered the claim was that it was done too late.
The plaintiff introduced a medical expert witness in an effort to establish that (a) a national standard of care exists as to when aspirin should be administered to avoid a clot in a post-splenectomy patient, and (b) here the surgeon breached that standard. The defendant’s position was, and is here, that the plaintiff failed to establish a national standard of care in support of his position. The issue is whether the trial court erred in granting the defendant’s motion for judgment on the basis that the plaintiff had failed (a) to effectively establish the national standard of care in these circumstances, and (b) to show the failure to administer aspirin was proximate cause of the injury suffered due to a deviation from the standard, each showing being required to establish medical malpractice. Allen v. Hill, 626 A.2d 875, 877 (D.C.1993).
II.
There was a hung jury and the trial court then granted a motion for judgment, filed pursuant to Super.Ct.Civ.R. 50(b) after a mistrial was declared. We review the grant of judgment in the light most favorable to the appellant. See, e.g., Spain v. McNeal, 337 A.2d 507, 508-09 (D.C.1975).
In a medical malpractice action, the plaintiff must prove the applicable standard of care, deviation from that standard and a causal relationship between the deviation and the injury. See, e.g., Washington v. Washington Hosp. Ctr., 579 A.2d 177, 181 (D.C.1990). In this jurisdiction, the applicable standard is a national standard, not just a local custom. See id. (citing Morrison v. MacNamara, 407 A.2d 555, 565 (D.C.1979)). In order to establish a national standard, “the plaintiff must establish through expert testimony the course of action that a reasonably prudent doctor with the defendant’s specialty would have taken under the same or similar circumstances.” Meek v. Shepard, 484 A.2d 579, 581 (D.C.1984) (footnote omitted). “The purpose of expert testimony is to avoid jury findings based on mere conjecture or speculation. The sufficiency of the foundation of those opinions should be measured with this purpose in mind.” Washington Hosp. Ctr., supra, 579 A.2d at 181 (citations omitted).
The personal opinion of the testifying expert as to what he or she would do in a particular case, without reference to a standard of care, is insufficient to prove the applicable standard of care. Thus, in Meek, supra, 484 A.2d at 581, the court ruled a doctor’s testimony insufficient where he never testified to a standard of care, “but rather stated only what he would do under similar circumstances” to those at issue. Similarly, in Toy v. District of Columbia, 549 A.2d 1, 8-9 (D.C.1988), the expert, although indicating that he had reviewed certain publications before testifying, insufficiently based his opinion as to the necessity of certain devices solely on his experience in a single jurisdiction.
There must be, then, evidence that a particular course of treatment is followed nationally. Reference to a published standard, though not required, can be important in determining whether a national standard’s adherence was proven with sufficiency. See *569Morrison, supra, 407 A.2d at 562-63 (availability of publications important to national standards requirement). Further, if there was evidence that the witness had discussed the described course of treatment with practitioners outside the District, such as at seminars or conventions, and that those other practitioners agreed with the course urged, the testimony might have been sufficiently supported since it would have been based upon “adequate data.” Sponaugle v. PreTerm, Inc., 411 A.2d 366, 367 (D.C.1980). Without such proof, there is no indication that the described standard is followed nationally, except the notion that what is done by certain District doctors is nationally followed because the District’s doctors are required to adhere to national standards. But that is just another way of saying that the applicable standard is what the testifying expert would have performed, which we have deemed an inadequate showing. See Meek, supra, 484 A.2d at 581-82.
Essentially, appellant’s medical expert witness testified that support for his opinion in relation to treatment by aspirin after the operation rested on discussions with about five or six local fellow surgeons.2 He testified, “It is the consensus of opinion of all the surgeons with which I have worked with and taught with that we do use aspirin when it reaches about two times normal.” He did not relate any basis for a further statement that other physicians around the country held the same viewpoint. He merely stated that he attended various medical conferences all over the country where doctors would discuss medical issues. The expert further admitted, however, that “I can’t say indeed that we discussed this particular post sple-neetomized patient and whether or not we should give aspirin in plate — we know we do.”
Clearly, this does not show the existence of a national standard since the expert admitted that he may or may not have discussed this at various national conferences. Moreover, the .expert admitted that he discussed this medical issue with only five or six other general surgeons in the Washington metropolitan area. When asked on cross-examination the basis for his testimony that the national standard requires the giving of aspirin when the platelet count following a sple-nectomy reaches between 700,000 and 800,-000, the expert replied, “I said aspirin is indicated, and it is indicated.” The expert was again asked whether “it was your testimony here today that [the giving of aspirin] is mandatory,” to which the expert replied, “For me it is.” Again, the expert expressed a personal opinion rather than a national standard of care.
Significantly, the expert was unable to specify any published medical standards, manuals, or protocols to support his opinion. Appellant provided only generalizations that were unsupported by any specific medical literature. On cross-examination the District asked, “But you can’t show us that [giving aspirin is a usual and customary practice] in any literature or in any hospital protocol, it’s only your personal opinion, isn’t it?” The expert then replied, “No, it’s not my only personal opinion. General surgeons generally do this.” The expert further testified, “the majority of surgeons would have institute[d] [aspirin] at that phase, and that is indeed my opinion and that is indeed what most of the doctors that I’ve talked to ... do use.”3 Finally, when asked whether he could point to a journal, textbook, or medical *570periodical, where this national practice was part of a hospital protocol, the expert stated, “Nor am I going to try.” The expert failed to provide any factual basis for his assertion that his testimony reflected a national standard other than his conversations with five or six colleagues within the District.4
Thus, appellant failed to establish a national medical standard in support of his position relating to the administration of aspirin after a splenectomy. This was fatal to his case because, to prevail here, he was required to establish that there was deviation from a national standard of care.
III.
Appellant also failed to show that the conduct of the attending physician was the proximate cause of his injury. In order to establish proximate cause, “[t]he expert need only state an opinion, based on a reasonable degree of medical certainty, that the defendant’s negligence is more likely than anything else to have been the cause (or a cause) of the plaintiffs injuries.” Psychiatric Inst. of Washington v. Allen, 509 A.2d 619, 624 (D.C.1986). The expert, however, recognized that it could not be determined in what part of the body the offending arterial clot originated. He also acknowledged that the patient (appellant) suffered from pre-existing arteriosclerosis, which was a potential source of the blood clots which caused the gangrene, necessitating the amputation. Thus, there was no evidence to show that the blood clot formed subsequent to the splenectomy, nor was there any testimony that aspirin would have halted the migration of a pre-existing blood clot.
IV.
Appellant failed (a) to establish that a national standard of care required a physician to administer aspirin to a post-splenectomy patient with a platelet level twice the normal, and (b) to present a prima facie case of proximate cause. Accordingly, the decision of the trial court is
Affirmed.
. A splenectomy refers to the removal of the spleen.
. Appellant’s medical expert received medical training at Howard University where he also completed his residency. The expert practiced in the District as a general surgeon, and maintained privileges at Hadley Memorial Hospital, Howard University Hospital, and D.C. General Hospital. He had trained interns and residents in surgery at D.C. General Hospital. Although the medical expert was licensed to practice medicine in Maryland, he had never actually done so. The only evidence that the expert had been exposed to the practice of medicine outside the District was his six-month employment with the Department of Defense in 1961 as a "civilian officer” at Fort Meade in Maryland. At the trial, the expert testified that splenectomy was not part of his own surgical practice and that he "thinks” he had performed one in the last ten years.
. The expert testified that "I have not talked to anyone other than the [doctors] in the Washington metropolitan area_ I ... am familiar that our practice ... is no different from any other practice in the country_” The expert, however, failed to explain the basis for this general assertion other than his conversations with five or six local surgeons.
. The dissenting opinion cites to the Framing-ham study relied on by the expert. This study, however, was done by cardiologists who gave aspirin to heart patients to prevent the extension of myocardial infarction. The expert admitted, however, that the situation in this case "is an entirely different scenario.”