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Medical Forum / General / General / March 2008Conversion factor for lab values
I realize that you'll think that I failed high school math -- maybe even grade school -- but I'm having lots of difficulty converting pg/mL (picograms per milliliter) into ng/dL (nanograms per deciliter). This is not helped by Google results that do lots of handwaving and in one case seem to confuse nanograms (ng) with milligrams (mg), a rather critical typo if that's really what it is. So could someone please give me a formula in an easy-to-understand format such as: "To find nanograms per deciliter multiply picograms per milliliter by 'n'." An example might help too. TIA >I realize that you'll think that I failed high school math -- maybe >even grade school -- but I'm having lots of difficulty converting [quoted text clipped - 8 lines] >"To find nanograms per deciliter multiply picograms per milliliter by >'n'." The short answer is: DIVIDE by 10. It's not something you missed from math, but from chemistry. Dimensional analysis, a name for a type of unit conversions, doing one step at a time, methodically. It really helps with more complex cases. For an example of a good presentation, see http://oakroadsystems.com/math/convert.htm But typing dimensional analysis is not easy, so let's try to walk thru it "logically", but slowly. First, do one thing at a time. Do not try to convert pg/mL to ng/dL. Convert pg to ng. And convert mL to dL. pg --> ng. ng is a bigger unit, so we need fewer of them. 1000 times bigger, so we need 1/1000 as many of them. So, divide by 1000. mL --dL. dL is bigger, 100 times bigger. So divide by 100. But this unit is in the denominator, so that becomes multiply by 100. Summary: Divide by 1000 and mult by 100. Overall, divide by 10. Writing out a more formal dimensional analysis does the above, but keeps the numbers and the up/down straight for you. bob >I realize that you'll think that I failed high school math -- maybe >even grade school -- but I'm having lots of difficulty converting [quoted text clipped - 8 lines] >"To find nanograms per deciliter multiply picograms per milliliter by >'n'." An example might help too. The trick in handling units and unit conversions is 'do arithmetic with the units'. Like so: 1 nanogram = 1000 picograms 1 deciliter = 100 milliliters or 1 nanogram 1 deciliter ---------- ----------- 1000 picograms 100 milliliters so if you've got 42 pg/ml and you want to convert to ng/dl, you do it like this: 42 pg/mL * 1ng/1000pg * 100 mL/1dL = 42 * (pg * 1 * ng * 100 * mL) ------------------------- = (mL * 1000 * pg * 1 * dL) 42 * (pg/pg * mL/mL * 1 * 100 * ng/dL) / 1000 i.e. you 'cancel out' the units as if they were algebraic symbols and you get: 42 * (100/1000)ng/dL = 42 * 0.1ng/dL or 42 pg/mL = 4.2 ng/dL This is a general method that's based on the notion that n/n is always one. Note that it's very useful when stuff comes in all kinds of units as in undergrad (or high school) physics problems, where they give you all kinds of numbers and the result has to be e.g. work or acceleration or whatever. If you carry the units along, and the result comes out in the wrong kind of units, you know you set it up wrong or made anotehr mistake somewhere. If you're unfamiliar with the metric system, learn the list of prefixes such as milli, micro, nano, etc and what they mean in powers of ten, but this method works for all kinds of conversions in or between any systems. I hope this helps you with this and any future conversion problems! >>I realize that you'll think that I failed high school math -- maybe >>even grade school -- but I'm having lots of difficulty converting >>pg/mL (picograms per milliliter) into ng/dL (nanograms per deciliter). <snip> >I hope this helps you with this and any future conversion problems! Thanks to both you and Bob for your easy-to-understand explanations. Now that you've done that perhaps you could help me with the reason for the needed conversion: I read on various websites that my testosterone/estrogen ratio should be around 20:1 ... or 50:1 if I'm a teenager... or some number in between... Like most of these things the number is remarkably vague. I would imagine that you have to convert the values to the same base but if we do that... My total T is 740 ng/dL and total estrogens are 57 pg/mL so converting the estrogens to ng/dL we get 5.7 which as a ratio is 130:1! Yikes! (BTW the RR for total E is 40 - 115 so it's not like I'm that bizarre). Well, maybe these ratio pushers are using E2 (estradiol) instead of total E but in that case it's even stranger. My E2 is 32 pg/mL so converted it becomes 3.2 ng/dL to give a ratio of 231:1! Weird! If I don't convert using total E (57) I get a ratio of 13:1 which would seem more reasonable given the "ratio pushers" claimed 20:1 or 50:1 but is this a valid way of doing a ratio like this? Just use the raw numbers without regard to what they represent? One medline abstract (Japanese IIRC) reported that they converted. They specifically stated that they did for ratio calculation and also said that but that other numbers in their study were in the normal units. However most of the ratio proponents are in the "dogmatic rules with absolutely no evidence" category (nutrition and life extension types) and none of them spell out the results of having a high or low ratio. For ex: at 10:1 you'll watch at least one chick flick per week and love cuddling; at 50:1 you'll look like Arnold Schwartzenegger in his prime and actually carve notches in the bedposts. (Just joking!) Any suggestions or should I just give up? >Now that you've done that perhaps you could help me with the reason >for the needed conversion: ... >Any suggestions or should I just give up? Please ask your doctor about this. S/he knows why your hormones were measured, and can help you interpret them in your personal context. The people most likely to give you a direct answer to your question here are those least qualified to do so. bob >>Now that you've done that perhaps you could help me with the reason >>for the needed conversion: >>Any suggestions or should I just give up? >Please ask your doctor about this. S/he knows why your hormones were >measured, and can help you interpret them in your personal context. >The people most likely to give you a direct answer to your question >here are those least qualified to do so. >bob You might be good at conversion formula but you obviously know zilch about MD's. Their knowledge regarding hormones is about as good as my knowledge of nuclear physics (i.e., abysmal) which is due at least in part to the lack of knowledge of the subject by the appropriate research people (those who write the textbooks and papers for medline). The other major factor is the speed, quantity and complexity of the changes since the MD went to school even if he graduated last week. I feel sorry for them for their inability to keep up; I feel far less sorry when they undeservedly claim authority (or you do it on their behalf). My hormones were measured because I told my PCP to write a prescription for the lab to do the work. He might not write me an Rx for Oxycontin but short of that (and similar) he'll do pretty much what I tell him. That's the way it should be; it's my money and body after all. As to your comment regarding the low qualifications of those likely to answer, that may or may not be the case. The best reply would be from someone who has already investigated the issue and has some personal or authoritative information. Maybe not likely on sci.med especially due to the crank factor but it does occur on other groups (e.g. sci.med.prostate.bph). If you don't ask you'll never know. On Mar 12, 7:31 pm, John...@WrongISP.gov wrote: > >>Now that you've done that perhaps you could help me with the reason > >>for the needed conversion: [quoted text clipped - 7 lines] > You might be good at conversion formula but you obviously know zilch > about MD's. I think I know quite a bit about MD's and their use of the clinical laboratory involving hormone testing. Their knowledge regarding hormones is about as good as my > knowledge of nuclear physics (i.e., abysmal) Not quite true as hormone issues are fairly common. which is due at least in > part to the lack of knowledge of the subject by the appropriate > research people (those who write the textbooks and papers for > medline). Research is not clinical medical practice. Research is exactly that research meaning it's unsubstantiated preliminary findings that must be confirmed by more or larger studies in order to validate such findings. The other major factor is the speed, quantity and complexity > of the changes since the MD went to school even if he graduated last > week. I feel sorry for them for their inability to keep up; I feel far > less sorry when they undeservedly claim authority (or you do it on > their behalf). Medicine does not change overnight and in fact is very slow to change. Certainly not from one week to another. The specialist educate the generalist of which they receive referrals from. You are not really involved in medicine. > My hormones were measured because I told my PCP to write a > prescription for the lab to do the work. He might not write me an Rx > for Oxycontin but short of that (and similar) he'll do pretty much > what I tell him. That's the way it should be; it's my money and body > after all. Unfortunately you got what you paid for meaning somebody who does what you tell him to and then disregards your lab ordered report or plays dumb to shut you up. I would like to think that as the alternative being he really isn't that bright and would do anything you suggested which is why you picked him. Again you got what you wanted. An endocrinologist would have thrown you out of his office for demanding anything. > As to your comment regarding the low qualifications of those likely to > answer, that may or may not be the case. The best reply would be from > someone who has already investigated the issue and has some personal > or authoritative information. Maybe not likely on sci.med especially > due to the crank factor but it does occur on other groups (e.g. > sci.med.prostate.bph). If you don't ask you'll never know. Without any clinical context then one can not provide anything useful. I personally find it hilarious that you have to come here to find conversion factors that should have already been included in the report if they were important. Testosterone and estradiol ratios are not reported as you can tell from your report. The fact is testosterone is almost always either free testosterone or total testosterone and virtually never with a estradiol included. Estradiol is for the ladies. I have seen more HCG's on males, which is rare in and of itself and never an estradiol, done on a male. This tells me that the ratio isn't in clinical use but research tools that have been used for many years in which to characterize hormonal levels in studied subjects and as stated clinical use is entirely different. >On Mar 12, 7:31 pm, John...@WrongISP.gov wrote: >> >>Now that you've done that perhaps you could help me with the reason [quoted text clipped - 4 lines] >> >The people most likely to give you a direct answer to your question >> >here are those least qualified to do so. >> You might be good at conversion formula but you obviously know zilch >> about MD's. >I think I know quite a bit about MD's and their use of the clinical >laboratory involving hormone testing. Your opinion. Based on the rest of what you say, I maintain mine. >Their knowledge regarding hormones is about as good as my >> knowledge of nuclear physics (i.e., abysmal) >Not quite true as hormone issues are fairly common. The issues might be common; the knowledge is poor. [I'm really only talking about the sex hormones. I'll plead lack of knowledge about the rest. Hopefully they're better informed about those although my gut feel says they aren't.] > which is due at least in >> part to the lack of knowledge of the subject by the appropriate >> research people (those who write the textbooks and papers for >> medline). >Research is not clinical medical practice. Research is exactly that >research meaning it's unsubstantiated preliminary findings that must >be confirmed by more or larger studies in order to validate such >findings. Research is where the cutting edge is. Research includes those larger studies. Most textbooks these days include massive footnotes that reference where the textbook-writer got his information (the research studies). The textbooks and studies form the theoretical and most-of-the-time practical knowledge of the current state-of-the-art in clinical practice. >The other major factor is the speed, quantity and complexity >> of the changes since the MD went to school even if he graduated last >> week. I feel sorry for them for their inability to keep up; I feel far >> less sorry when they undeservedly claim authority (or you do it on >> their behalf). >Medicine does not change overnight and in fact is very slow to change. The basis changes very rapidly (all those studies and new editions of textbooks) but you're right, the clinician is slow to change and thus out-of date. Just what I said. >Certainly not from one week to another. The specialist educate the >generalist of which they receive referrals from. You are not really >involved in medicine. As a consumer I am. You, however, seem to live in a fantasy world that resembles the UK. Specialists educating the PCP...ROTFL ... maybe in medical school. >> My hormones were measured because I told my PCP to write a >> prescription for the lab to do the work. He might not write me an Rx >> for Oxycontin but short of that (and similar) he'll do pretty much >> what I tell him. That's the way it should be; it's my money and body >> after all. >Unfortunately you got what you paid for meaning somebody who does what >you tell him to and then disregards your lab ordered report or plays >dumb to shut you up. I would like to think that as the alternative >being he really isn't that bright and would do anything you suggested >which is why you picked him. Hmmm. That must be why he makes New York magazine's list of best physicians (internal medicine) year after year. > Again you got what you wanted. An >endocrinologist would have thrown you out of his office for demanding >anything. Any endocrinologist who didn't do what I wanted would be fired very quickly. (Just think of what you're saying here: The supplier of whom you're requesting a service has the gall to "throw you out of his office for demanding anything." Is there any other industry where such an attitude would be tolerated, even condoned and supported by some customers?) >> As to your comment regarding the low qualifications of those likely to >> answer, that may or may not be the case. The best reply would be from >> someone who has already investigated the issue and has some personal >> or authoritative information. Maybe not likely on sci.med especially >> due to the crank factor but it does occur on other groups (e.g. >> sci.med.prostate.bph). If you don't ask you'll never know. >Without any clinical context then one can not provide anything useful. Sure they can. Making a statement like that is effectively saying (for example) that it's useless reading "Endocrine Replacement Theory in Clinical Practice" (Contemporary Endocrinology series by A.Wayne Meikle) ... that the theory is not important. >I personally find it hilarious that you have to come here to find >conversion factors that should have already been included in the >report if they were important. Why would the lab include those? They don't offer such. Moreover the reason for the query about the conversion factor was to see (on a theoretical basis) if I was doing the right conversion, so bizarre were the results. Further, the underlying basis for interest in the ratios has to do with the cutting edge theory (or conjecture) --not mine -- that BPH (benign prostatic hyperplasia) has less to do with the level of DHT than with a surfeit of estrogens, the estrogens protecting the cells from apoptosis. I hardly think a commercial lab would have a test based on an as-yet-not-firmly-established theory. > Testosterone and estradiol ratios are >not reported as you can tell from your report. The fact is >testosterone is almost always either free testosterone or total >testosterone and virtually never with a estradiol included. Nonsense. Estrogens are essential to male health. If MD's don't request them it's just another example of poor (and obsolete) medicine. Moreover due partially to the poor performance of labs in determining free T, the currently used (or should be used) tests are for bioavailable T. This includes free T and the portion bound to albumin, the latter being able to disassociate itself easily. Some (probably most) MD's are still agonizing over total T (see above regarding up-to-date). > Estradiol >is for the ladies. Really! Try driving your E down to zero for a few years. Your loss of BMD should change that attitude. Other nasty things will occur too. > I have seen more HCG's on males, which is rare in >and of itself and never an estradiol, done on a male. Huh! HCG is Human Chorionic Gonadatrophin a drug/biologic agent used to effect an increase in T without resorting to replacement, a technique of major importance when it comes to fertility. The only uses of a test for endogenous HCG is in pregnant females and a minor use in males for the confirmation of testicular tumors. Nothing to do with what we're talking about. > This tells me >that the ratio isn't in clinical use but research tools that have been >used for many years in which to characterize hormonal levels in >studied subjects and as stated clinical use is entirely different. See above. On Mar 13, 8:30 pm, John...@WrongISP.gov wrote: > >I think I know quite a bit about MD's and their use of the clinical > >laboratory involving hormone testing. > > Your opinion. Based on the rest of what you say, I maintain mine. My opinion based on thirty years of performing clinical laboratory work involving endocrinology. You are welcome to yours but mine is evidence based and experience based. > >Their knowledge regarding hormones is about as good as my > >> knowledge of nuclear physics (i.e., abysmal) [quoted text clipped - 4 lines] > rest. Hopefully they're better informed about those although my gut > feel says they aren't.] Again the emphasis is on clinical medical terms and not esoteric physiology that really isn't clinically relevant. I am more aware of the clinically relevant medical context. > > which is due at least in > >> part to the lack of knowledge of the subject by the appropriate [quoted text clipped - 11 lines] > most-of-the-time practical knowledge of the current state-of-the-art > in clinical practice. Look up any medical text books involving clinical endocrinology. I don't know what text books you refer to. Yes indeed there are many books although most do not reflect the latest research because of the problems associated with cutting edge research. It reminds me of the Noble laureate who others could not replicate his works and he was forced to withdraw his paper in Nature magazine. It takes years to write medical texts and the fresh off the press research is only mentioned as curiosities and not as common clinical practice. > >The other major factor is the speed, quantity and complexity > >> of the changes since the MD went to school even if he graduated last [quoted text clipped - 6 lines] > textbooks) but you're right, the clinician is slow to change and thus > out-of date. Just what I said. It takes years to write a text and by the time it comes out in press it is five years behind the present research. That isn't necessarily bad as most research doesn't pan out, is redundant or not better than what was is presently in use. Something must be better than what is in present use. The present use has the advantage of many years in clinical practice and all the warts are known. > >Certainly not from one week to another. The specialist educate the > >generalist of which they receive referrals from. You are not really [quoted text clipped - 3 lines] > resembles the UK. Specialists educating the PCP...ROTFL ... maybe in > medical school. The PCP sends patients to the specialist and reports are handed to the PCP on how to deal with the case. The PCP must and does learn to deal with general internal medical issues. The take care of the whole patient in which the specialist only really has limited knowledge in. If you thought it was so funny then why didn't you go to an endocrinologist and not your PCP? > >> My hormones were measured because I told my PCP to write a > >> prescription for the lab to do the work. He might not write me an Rx [quoted text clipped - 9 lines] > Hmmm. That must be why he makes New York magazine's list of best > physicians (internal medicine) year after year. I don;t think he made it by having you ordering tests and then him not understanding them. > > Again you got what you wanted. An > >endocrinologist would have thrown you out of his office for demanding [quoted text clipped - 6 lines] > an attitude would be tolerated, even condoned and supported by some > customers?) No wonder you go to PCP for that and not an endocrinologist and so you are left wondering. > >I personally find it hilarious that you have to come here to find > >conversion factors that should have already been included in the [quoted text clipped - 9 lines] > protecting the cells from apoptosis. I hardly think a commercial lab > would have a test based on an as-yet-not-firmly-established theory. Cutting edge theory is not clinical practice again you confuse the two. Theories are a dime a dozen. There are many tests out there which cater to all practitioners out there. Some are FDA approved and others are for research purposes only. > > Testosterone and estradiol ratios are > >not reported as you can tell from your report. The fact is [quoted text clipped - 9 lines] > (probably most) MD's are still agonizing over total T (see above > regarding up-to-date). No one said estrogens are not essential. The clinical relevance is what dictates laboratory use and not how essential something is. So not all doctors, PCP and endocrinologist practicing medicine are obsolete because they don't latch on to present theories. It's up to the proponents of the research to prove their case from theory to clinical relevence in the practice of medicine. > > Estradiol > >is for the ladies. [quoted text clipped - 11 lines] > use in males for the confirmation of testicular tumors. Nothing to do > with what we're talking about. Now you are learning clinical relevant use. The rest is pretty much toying with your hormones. The use of hormone assays are for the diagnosis, treatment and monitoring of clinical conditions. Basement experiments are for researchers playing with rats. > > This tells me > >that the ratio isn't in clinical use but research tools that have been > >used for many years in which to characterize hormonal levels in > >studied subjects and as stated clinical use is entirely different. > > See above. You won't see a ratio stated if one were ever to include a TT and Estradiol because there is no stated reference range. By law and regulations when ever something is reported a valid and referenced range must be reported. It isn't clinically relevant and there is no agreed upon reference range because it's simply for research purposes. You got the tests done but no ration stated for the reasons above. When ever anything is performed for research purposes it must clearly be stated as such and the patient must be advised if such research is being undertaken. Performing research without a consent and cause problems. >>>Now that you've done that perhaps you could help me with the reason >>>for the needed conversion: [quoted text clipped - 32 lines] >due to the crank factor but it does occur on other groups (e.g. >sci.med.prostate.bph). If you don't ask you'll never know. I appreciate many of the points you made. Of course, points we make here very briefly are likely to be simplified/exaggerated, and I won't worry about that. My basic point is that your physician is the place to start. S/he should be able to "translate" the lab report into English for you, and answer the factual parts of your questions. S/he can also give you a professional opinion of what they mean -- in the context of your personal situation. I appreciate the possible value of "support groups", which exchange info and give you ideas -- not just some crank telling you what odd procedure to blindly follow. Doctors do know a lot, and they are trained to think about "the whole person". At least, in principle they are. And they do [try to] keep up. And yes, I am being idealistic. Real doctors vary. But it is the place to start. As an example... You asked about normal ratios of certain components. But then the question becomes, what if one's ratios are not quite "normal"? It is not obvious without special knowledge that there is any problem. I may be over-reading your intent in asking the question, which is why I am bothering to elaborate a bit here. bob >>>bob Hang on there, didn't I just reply to "Bob" aka Robert1? My mistake. Obviously Bob and Robert1 are not the same. Sorry. <snip> >My basic point is that your physician is the place to start. S/he >should be able to "translate" the lab report into English for you, and >answer the factual parts of your questions. S/he can also give you a >professional opinion of what they mean -- in the context of your >personal situation. I realize this is the standard/accepted/PC reply however it's something I'd like to break people of doing [is that English?] as much as I can. It's incorrect, at least in my experience in those areas I've had the opportunity to study in depth. That doesn't augur well for the MD's knowledge in those areas I haven't pursued. There's a couple of examples in my reply to Robert1 (failure to test for E or E2, reliance on unreliable Free T values, etc.) Getting more esoteric (questions I could ask my MD <g>): What's the difference between E2, E1, and E3 (functions)? If E (in general or E2 if you prefer) can effectively occupy the sex hormone receptors in the hypothalamus (this causes proportionate shutdown in the production of GNRH) what is the ratio (damn those ratios <g>) of E (or E2) to T necessary to effect the same change? IOW if I knock down my E2 by (say) 10pg/mL how much will this raise T? (I can partially answer the first part; to the second I'd say ask a patient/customer on a friendly NG who has actually done it, your average MD won't have a clue.) <snip> >As an example... You asked about normal ratios of certain components. >But then the question becomes, what if one's ratios are not quite >"normal"? Not normal, optimal! 20/40 is normal eyesight for a 60 year old; optimal is 20/20. No one knows what the optimal (or ideal) ratios are. The people who are proposing them are just wildly grabbing at straws. If we work on the basis that teenagers are the most healthy group in the population you should either raise T or lower E to get closer to the teen ratio subject to not putting your E levels too low for adequate functionality. We don't know what the teenage levels are (other than some vague dubious claims on some websites) so we need more info there (maybe I should ask my MD? <g>) but we do have some reasonable info on the cut off for E levels courtesy of the use of aromatase inhibitors in females suffering from BCa. There's some info on males too. > It is not obvious without special knowledge that there is >any problem. I may be over-reading your intent in asking the question, >which is why I am bothering to elaborate a bit here. Hmmm, OK, but one doesn't necessarily have to have a problem to take pre-emptive action.
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