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More on Low Factor X, Normal PTT

Here is a follow-up comment from Dr. Larry Brace, Edward Hospital, Naperville, IL.

With regards to the patient with pubertal menorrhagia, has anyone tested the parents? If this is an inherited X deficiency, both parents would need to be heterozygous in order to have a child that has 1% factor X. If both parents have normal X activity, then it must be assumed that the patient has an acquired X deficiency, or that the patient is adopted. There is a fairly long list of conditions that cause acquired X deficiency, but most would not be suspected in such a young patient.

In addition, I would also suggest testing factor X by a chromogenic X assay. This would ameliorate the issue involved in different PT and PTT reagents used in most X activity assays. The patient should also be tested for factor X antigen.

Here is an additional comment from Vilas Hiremath on the same issue:

Dear George, Why is PTT normal in factor X deficiency? Because PT is more sensitive than PTT for the detection of vitamin K-dependent coagulation factors like factor X.

Response from George:

While it doesn’t answer Vilas’ question about why only the PT is affected, I like Dr. Brace’s suggestions, which can be used to confirm factor X deficiency. The unusual PT and PTT results make it necessary to reach a conclusion. I’m not sure that I agree with Vilas’ assertion that the PT is more sensitive than the PTT for factor X, I believe both are equally sensitive, within the limits of their developers’ specifications. Nevertheless, the issue raises uncertainties that will hopefully draw further discussion.

Comments (2)
Jul 4, 2011 2:01am

Dear Vilas, please clarify your phrase: “with normal PTT and
Dear Vilas, please clarify your phrase: “with normal PTT and factor X & It; 1%” Did you mean to write “factor X & II? Geo.

Jun 20, 2011 8:27pm

Dear George,
I have repeated with fresh sample today (June

Dear George,
I have repeated with fresh sample today (June 20, 2011), her results are same: PT prolonged with normal PTT and Factor X & lt; 1%. LA screen prolonged but ratio normal. Her sister’s coagulation work up shows normal study.
with regards, Vilas Hiremath

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