06-15-2010, 11:51 AM
The correct answer is D. This patient is undernourished
and in a neglected state of health.
Often, the only manifestation of poor nutrition
in an elderly patient is subtle changes in routine
laboratory values including creatinine, a
reflection of decreased muscle mass; albumin,
a reflection of poor protein intake; and calcium.
Because active, ionized calcium is only
a fraction (45%) of what is measured in total
calcium, there are some settings in which a
low total calcium measurement does not reflect
overall calcium depletion. Specifically,
when circulating albumin levels are decreased,
the 40% of total calcium that is normally
bound to albumin is also low, and calcium
measurements will be demonstrably low. In-
deed, for each 1 g/dL reduction in albumin
levels, the total calcium concentration will be
lowered by 0.8 mg/dL. This reduction does
not represent a reduction in ionized calcium,
and thus will not cause clinical hypocalcemia.
Answer A is incorrect. Blood urea nitrogen
(BUN) levels correlate to dietary intake and
hydration status. In an undernourished elderly
woman, it is not surprising that as protein intake
decreased, BUN dropped slightly. BUN,
however, plays no role in the measurement of
total or ionized calcium levels.
Answer B is incorrect. Creatinine levels correlate
to lean muscle mass levels. In an undernourished
and elderly woman, it is not surprising
that creatinine levels are subnormal.
Creatinine levels, however, play no role in the
measurement of total or ionized calcium levels.
Answer C is incorrect. Because creatinine
plays no role in determining calcium levels,
this answer is incorrect.
Answer E is incorrect. Decreased serum albumin
levels lead to an underestimation of clinically
important calcium levels. Aggressive calcium
repletion is not warranted.
and in a neglected state of health.
Often, the only manifestation of poor nutrition
in an elderly patient is subtle changes in routine
laboratory values including creatinine, a
reflection of decreased muscle mass; albumin,
a reflection of poor protein intake; and calcium.
Because active, ionized calcium is only
a fraction (45%) of what is measured in total
calcium, there are some settings in which a
low total calcium measurement does not reflect
overall calcium depletion. Specifically,
when circulating albumin levels are decreased,
the 40% of total calcium that is normally
bound to albumin is also low, and calcium
measurements will be demonstrably low. In-
deed, for each 1 g/dL reduction in albumin
levels, the total calcium concentration will be
lowered by 0.8 mg/dL. This reduction does
not represent a reduction in ionized calcium,
and thus will not cause clinical hypocalcemia.
Answer A is incorrect. Blood urea nitrogen
(BUN) levels correlate to dietary intake and
hydration status. In an undernourished elderly
woman, it is not surprising that as protein intake
decreased, BUN dropped slightly. BUN,
however, plays no role in the measurement of
total or ionized calcium levels.
Answer B is incorrect. Creatinine levels correlate
to lean muscle mass levels. In an undernourished
and elderly woman, it is not surprising
that creatinine levels are subnormal.
Creatinine levels, however, play no role in the
measurement of total or ionized calcium levels.
Answer C is incorrect. Because creatinine
plays no role in determining calcium levels,
this answer is incorrect.
Answer E is incorrect. Decreased serum albumin
levels lead to an underestimation of clinically
important calcium levels. Aggressive calcium
repletion is not warranted.