Solving the Puzzle: Case Studies In Coaguation

by Donna Castellone, MS, MT (ASCP) SH • April 14, 2022

The interpretations below are provided by Donna Castellone, MS, MT (ASCP) SH for Aniara Diagnostica.

I haven’t always liked puzzles. I didn't do them much growing up, I did them with my kids, and during lock down we became addicted to them. Then I realized I spent my life working on puzzles and putting the pieces together to solve problems in the laboratory. So many cases required pieces of patient history and testing that needed to be added to provide a piece to complete the puzzle. Here are some pieces to a few favorite puzzles for you to solve!


Elderly woman is transported to the ED from a skilled nursing facility for exacerbation of congestive heart failure. Patient has a history of atrial fibrillation, hypertension, diabetes and coronary artery disease. Patient was previously on warfarin which was stopped and rivaroxaban was started a few days ago. There are no signs or symptoms of abnormal bleeding.

Coagulation results on admission are as follows:

PT = 54 seconds (9-12 seconds)

INR= 4.9 (0.9-1.2)

APTT=48 seconds (24-36 seconds)

Admitting resident requested information on the INR therapeutic range for Rivaroxaban. Can you use the INR or the PT to provide information for rivaroxaban?



Rivaroxaban will prolong the PT and it is assay dependent however it is not appropriate to use the INR to monitor DOACs. Prolonged PT/INR likely due to residual warfarin and FXa inhibition by Rivaroxaban

Coagulation Labs 13 hours post-admission:

PT / INR = 40 seconds / 3.7 (9-12 seconds)

PT / INR mix = 19 seconds / 1.8

TT = 21 seconds (15-22 seconds)

APTT = 45 seconds (24-36 seconds)

APTT mix = 32 seconds

Anti-FXa = 2.1 IU/mL (hybrid heparin calibration)

Normal TT (ruled out heparin presence)

aPTT mix corrected completely (consistent with factor deficiencies)

PT mix remained prolonged (suggests inhibitory activity)



Elevated anti-FXa in the absence of heparin (consistent with presence of Rivaroxaban at a minimum of 18-24 hours following the last dose)
With a short half-life of rivaroxaban, the anti-FXa is higher than expected. An elevated creatinine clearance confirmed poor kidney function.
Rivaroxaban renally cleared, therefore unable to clear was discontinued and warfarin re-started.1



A 1 year old male with hemophilia admitted for FVIII treatment. Developed a hematoma after slamming finger in a draw. His arm presented with tenderness, was swollen, had minimal discomfort, with good pulse. He was active and alert. He was treated with 50 U/kg recombinate FVIII, they had trouble with IV access, no other issues he was discharges. He was infused with first generation recombinate which is derived from full FVIII gene contains both human albumin and animal proteins. Effective, a single dose can eliminate 80% of bleeds. Inhibitor development major concern, seen in up to 33% of patients because the immune system sees the derived DNA as a pathogen and tries to destroy and remove infused FVIII.2

The following day there was swelling and bruising where the IV attempts were tried. Additional FVIII was given and they were monitoring extremity to rule out compartment syndrome. Arm was warm to touch, additional digits swollen, missing radial pulse. Found a pulse on Doppler.

FVIII level was drawn 4 hours post infusion

aPTT= 85.6 sec

FVIII < 1%

TT= 16.4 sec

1:1 mix 77.8

Incubated 1:1= 80.4



What testing should be performed next? Mixing study did not correct?

no corrections

Lupus Testing

Screen= negative at 34.0 sec / confirm 32.9

HPP= screen 151.1

Confirm 143

Delta is 8

R/O non specific inhibitor


Bethesda testing was performed- neat 1:5, 1:10, 1:20 and 1:40

All results were 1%, unable to quantitate

Additional dilutions had to be performed

However they needed to treat the patient

INHIBITOR TO FVIII- We needed more sample to get a level, they needed to treat

Use bypass agent of recombinate factor VIIa (rFVIIa) or emicizumab.

rVIIa binds to the surface of activated platelets, where it supports thrombin generation, thus bypassing the need for FVIII. rVIIa is made from cultured mammalian cells and is free from human protein Difficult to monitor- can put a patient at a risk for thrombosis.3

Emicizumab (Hemlibra) Non-factor therapy is a humanized bispecfic antibody. It works by mimicking the cofactor activity of FVIII by bridging activated FIX and FX. The aPTT will be shortened in patients on emicizumab, often into the normal range even at low concentrations. In addition, one-stage aPTT based factor VIII activity assays will yield high factor VIII activities, even at low concentrations of the drug. Emicizumab is highly selective for human FIXa and FX, Only chromogenic FVIII assays using human reagents can assess emicizumab activity but those assays are not widely available.4



Next day tried to get them Bethesda titer: began with a 1:10 of the patient plasma

Continued the 5 dilutions. Still no measurable result. Reported out BU > 100

Begin regular factor infusions

Possible emicizumab injections

Good pulse and arm warm

No further testing due to not wanting to envoke further trauma and possible injury



33 year-old male admitted on an emergency basis to the Urology Service for gross hematuria for past week. Previously seen in the hospital for mild chest pain thought to be atypical angina pectoris. Managed with nitroglycerin, Cardilate 10 mg QID, and Inderal 10 mg QID.Negative bleeding history Family bleeding history negative but all four of his grandparents were brothers and sisters.

One week prior to admission, he had low back pain followed by gross painless hematuria Physical exam normal with few mild bruises on his legs.



Laboratory Results:

PT 60 sec. (11-13 sec)

aPTT >150 sec (25-37 sec)

HCT 32% (40-54%)

WBC 9,000/cmm (5-10,000/cmm)

Platelets 250,000/uL (130-400,000/uL

Fibrinogen 350mg/dl (200-450 mg/dl)

Thrombin 19 sec (18-22 seconds)

What are your initial thoughts as to a coagulopathy?

Is this a hereditary or acquired disorder?

What other coagulation tests would you perform?



Mixing studies: PT =13.1


aPTT= 35.7

PNP= 32.1

corrected with PNP FULL CORRECTION

II 7%

V 9%

VII 5%


X 11%

Fibrinogen 350 mg/dL

Multiple coagulation factor deficiencies affecting both intrinsic and extrinsic pathways

No history of bleeding, Fit picture of patient on oral anticoagulant. Drug history showed Inderal and Cardilate (10 mg each, four times daily). Strictly denied any other medications. Denied that anyone was “after him”, rat poison etc? Patient given 25 mg of Vitamin K and similar dose 6 hours later.

12 hours after first injection

PT= 12.5 sec

aPTT= 32.1 sec

all results normal

Family brought medications to hospital

Had Rx refilled approx. two weeks before and noticed one of the pills looked different

Wrong medication- Was given warfarin in place of Normal medications!!!



As I have said for years, coagulation is truly a puzzle. You need to be part scientist, part artist, and part detective to survive in this laboratory. Real life case studies, because you can't make this stuff up!



  1. Eby C. Novel anticoagulants and laboratory testing. Int J Lab Hematol. 2013; 35:262-8
  2. Thromb Haemost 2006;96:113-118
  3. ASH Education Book, January 1, 2006 vol. 2006 no. 1 432-437
  4. Lenting, PJ., Denis, CV., Christophe, OD., Emicizumab, a bispecific antibody recognizing coagulation factors IX and X: how does it actually compare to factor VIII?, Blood, 2017, 130:23