The_Basics

Question 1

Once glucose is greater than 200 mg/dL, sodium decreases by how many mEq/L for each rise of 100 mg/dL in glucose?

Answer 1

1.6 for every 100

Question 2

Acidosis causes what effects on potassium? on calcium?

Answer 2

hyperkalemic acidosis = hypercalcemia

hypokalemic alkalosis = hypocalcemia

Question 3

How do you correct calcium?

Answer 3

ca + 0.8 (4 - albumin)

Question 4

How do you distinguish Wilm’s tumor from neuroblastoma?

Answer 4

neuroblastoma: arise from adrenal gland (not kidney), calcifications. Can use a CT to distinguish.

Question 5

How do you distinguish Familial Hypocalciuric Hypercalcemia from Primary Hyperparathyroidism via urine studies?

Answer 5

UCa is < 100 in FHH, but > 250 in 1* PTH

Question 6

Histologic findings for Reye syndrome:

Answer 6

microvesicular fatty infilration

Question 7

List selection biases:

Answer 7

1) ascertainment: study population differs from target due to nonrandom selection
2) nonresponse
3) Berkson (only hospital patients in study population = not reflective of target)
4) Prevalence (Neyman): exposures that happen long before disease can miss those who recover or die early
5) attrition (loss of study participants to follow up)

Question 8

List observational biases:

Answer 8

1) recall bias (negative outcomes more likely to report exposures)
2) observer bias (due to preconceived expectations will misclassify data)
3) reporting bias (due to social stimga)
4) surveillance (risk factor causes increased monitoring in exposed group)

Question 9

What is the presentation of 17a-hydroxylase deficiency? Which hormones are elevated or depressed as a result? Are the levels of mineral corticoids, cortisol, and sex hormones increased or decreased?

Answer 9

HYPERtension, HYPOkalemia. Pregenolone and progesterone are elevated; 17-hydroxyprogesterone is decreased.

Ambiguous genitalia in geneitc males; externally phenotypical females with normal internal organs but no 2* sex characteristics

Increased mineralocorticoids, decreased cortisol, decreased sex hormones.

Question 10

What is the presentation of 21-hydroxylase deficiency? Which hormones are elevated or depressed as a result? Are the levels of mineral corticoids, cortisol, and sex hormones increased or decreased?

Answer 10

most common CAH. HYPOtension and HYPERkalemia. Hyponatermia. Increased renin activity, volume depletion. 11-deoxycorticosterone and 11-deoxycortisol are decreased. 17-hydroxyprogesterone is increased.

Masculinization, leading to pseudohermaphroditism in females.

Decreased mineralocorticoids, decreased cortisol, increased sex hormones

Question 11

What is the presentation of 11B-hydroxylase deficiency? Which hormones are elevated or depressed as a result? Are the levels of mineral corticoids, cortisol, and sex hormones increased or decreased?

Answer 11

HYPERtension. Masculinization. Decreased corticosterone, but increased 11-deoxycorticosterone (which is also a mineralocorticoid).

Masculinization.

Increased mineralocorticoids (11-deoxycortisone, but decreased aldosterone!!). Decreased cortisol. Increased sex hormones.

Question 12

Tamoxifen and raloxifene are both estrogen receptor antagonists in the breast but agonists in the bone = SERMS. Which one increases the risk of endometrial cancer?

Answer 12

Tamoxifen! It is an endometrial AGONIST in the endometrium, too.

**raloxifene is an endometrial antagonist in the endometrium so does not increase endometrial CA risk

Question 13

The obturator nerve is composed of which nerve roots?

What is a possible causes of injury?

What would be the motor deficit? Sensory deficit?

Answer 13

Obturator nerve = L2-L4

Injury: anterior hip dislocation

Motor deficit: thigh adduction

Sensory deficit: medial thigh

Question 14

The femoral nerve is composed of which nerve roots?

What is a possible causes of injury?

What would be the motor deficit? Sensory deficit?

Answer 14

Femoral nerve = L2-L4

Injury: pelvic fracture

motor deficit: thigh flexion, leg extension

sensory deficit: anterior thigh and medial leg

Question 15

The common peroneal nerve is composed of which nerve roots?

What is a possible causes of injury?

What would be the motor deficit? Sensory deficit?

Answer 15

common peroneal nerve: L4-S2

injury: trauma or compression of lateral aspect of leg. Fibula neck fracture.

motor deficit: foot EVersion and Dorsiflexion.

sensory deficit: anterolateral leg and dorsal aspect of foot

Question 16

The tibial nerve is composed of which nerve roots?

What is a possible causes of injury?

What would be the motor deficit? Sensory deficit?

Answer 16

tibial nerve: L4-S3

injury: knee trauma.

motor deficit: foot INversion and PLantarflexion; toe flexion

sensory deficit: sole of foot

Question 17

Can’t abduct thumb. When asked to make a fist, 2nd and 3rd digits remain extended/thumb unopposed.

Answer 17

Proximal median nerve lesion

Question 18

Dislocation of the humeral head or a fractured surgical neck of the humerus might cause which motor deficits? which sensory deficits?

Answer 18

damage to axillary nerve (C5, C6)

motor deficit: inability to abduct arm at shoulder. sensory deficit over deltoid.

Question 19

Compression of axilla by back of chair or crutches, or fracture at MIDSHAFT of humerus might cause which motor deficits/sensory deficits?

Answer 19

damage to radial nerve (C5-T1)

Inability to supinate, extend wrist and fingers, extend arm

sensory defict over posterior arm, dorsal hand, dorsal thumb

Question 20

Fracture to the supracondylar humerus might cause what motor/sensory deficits?

Answer 20

median nerve (C5-T1)

motor: loss of opposition of thumb, lateral finger flexion, wrist flexion
sensory: loss of (the tip dorsal and) palmar aspects of lateral 3 1/2 fingers

Question 21

Fracture of the medial epicondyle of the humerus might cause which motor/sensory deficits?

Answer 21

ulnar nerve (C8, T1)

motor: medial finger flexion, wrist flexion (will see a radial deviation). Claw hand (finger extensors, fed by radial nerve, will be unopposed)
sensory: medial 1 1/2 fingers, hypothenar eminence

Question 22

Ammonium magnesium phosphate (or “struvite”) stones are caused by

Answer 22

infection with urease-positive bugs (Proteus mirabilis, Staph, Kelbsiella, ureaplasma, pseudomonas, morganella). They hydrolyze urea to ammonia, causing urine alkalinization.

Can form STAGHORN calculi

Question 23

How does sensitivity affect PPV and NPV?

Answer 23

High sensitivity = low PPV, high NPV

Question 24

Using the 4x4 table, how is Odds Ratio calculated? How is relative risk calculated?

Answer 24

odds ratio: (a x d) / (b x c)

relative risk: [a/(a + b)] / [c/(c+d)]

Question 25

From what type of studies is odds ratio calculated?

Answer 25

retrospective studies (case-control)

Question 26

A 95% CI that does not contain the null value corresponds to a p value of:

A 99% CI that does not contain the null value corresponds to a p value of:

Answer 26

95%: p value of <0.01

Question 27

What is the difference between case-control studies and retrospective cohort studies?

Answer 27

In retrospective cohort studies, the risk factor espoxure is determined before the outcome is known, allowing for calculation of relative risk.

In a case-control study, outcomes are retrospectively associated with specific risk factors.

Question 28

What is the difference between effect modification and confounding?

Answer 28

Do a stratified analysis based on the variable of interest. If a strong association is seen = effect modification. If no significant difference = confounding.

Question 29

Intention to treat analysis helps against what kind of bias?

Answer 29

selection bias

Question 30

On an ROC curve (with sensitivity on one side and 100-specificity on the other), how is accuracy measured?

Answer 30

total area under the curve (closer the plotted curve gets to the left and top borders = more accurate test)

Question 31

How do you calculate attributable risk percent? = WHat percent of outcome can be associated to the factor of interest?

Answer 31

(RR - 1) / RR

Question 32

What is selective survival bias?

Answer 32

In case-control studies when cases are selected from the entire population instead of those just newly diagnosed

Question 33

What is the relationship of mean, median, and mode in normally distributed and skewed distributions?

Answer 33

normal: mean = median = mode

postiively skewed: mean > median > mode
negatively skewed: mode > median > mean