Showing posts with label Immunology. Show all posts
Showing posts with label Immunology. Show all posts

Friday, December 17, 2021

Job's syndrome

Job's syndrome is also known as hyper- IgE syndrome.
It has autosomal dominant inheritance ( STAT3 gene).

Here is the mnemonic to remember its key features :
A - Abscesses of face and lungs by staphylococcus aureus ( pneumatocele)
B - Bone fragility
C - Coarse facies
D - Dermatological features like eczema.
E - Eosinophilia, increased Ig E.

Trick to remember important points: 
"Steve Jobs is a dominant person, interested in business STATs"

That's all!
Dr. Madhuri.


Thursday, May 27, 2021

Fact of the day - hypercalcemia in sarcoidosis

 Hi!


Hypercalcemia and hypervitaminosis-D is seen in patients with sarcoidosis and other granulomatous inflammatory conditions. This is because the granulomatous macrophages have high 1-alpha hydroxylase activity --> high levels of 1,25-OH2 vitamin D (calcitriol), produced in addition to this enzyme's normal activity in the kidneys.


That's all

- Jaskunwar Singh

Thursday, May 20, 2021

Types of COVID-19 antibody tests

Hi everyone! 

In this post, I will go over in very short the different types of  COVID-19 antibody tests.

Saturday, April 24, 2021

Ampicillin-rash in infectious mononucleosis

 Hi!


Penicillins such as amoxicillin and ampicillin are currently not recommended in patients with infectious mononucleosis with bacterial secondaries (streptococcal tonsillo-pharyngitis). Why?

Saturday, January 2, 2021

The Moderna Vaccine: End of Pandemic?

 

The Moderna (mRNA-1273) SARS-CoV-2 vaccine is the second vaccine to receive emergency use authorisation (EUA) by the FDA. Like the Pfizer vaccine, it is also a lipid nanoparticle encapsulated mRNA vaccine, and therefore has the same mechanism of action. Please read about the brief mechanism from the Pfizer vaccine article: https://www.medicowesome.com/2020/12/the-bnt162b2-covid-19-vaccine-pfizer.html I will try to avoid big numbers and statistics in this article. 

Both Moderna and Pfizer vaccines start protecting their recipients 10 days after the first dose, with maximum protection two weeks after the second dose. They both have efficacy ranging from 94-95% in protecting against symptomatic Covid-19. However, studies haven't yet evaluated their role in preventing asymptomatic Covid-19, a substantial missing link. 


Can Covid-19 vaccines mitigate the pandemic? 

People picture vaccines as a way back to normalcy, as before the pandemic; unless these mRNA vaccines' role in controlling asymptomatic SARS-CoV-2 infection is studied, normalcy is out of our reach. The other issues concerning the above question are -

1. Since the phase 3 studies of these vaccines are relatively 'young', we don't have sufficient knowledge about the nature and duration of immunological protection. Animal studies have shown that neutralizing antibodies confer protection and CD4 and CD8 T cells also amplify the immunological response. We don't know how long will the neutralizing antibodies last in our plasma after receiving the vaccine. 

2. With both these vaccines, there is an inevitable study flaw. Vaccine recipients faced more systemic adverse events, such as fever, fatigue, headache, myalgia than the placebo group. These symptoms can also occur with Covid-19. Therefore, it is not unlikely that vaccine recipients could have designated their symptoms to the 'shot', and hesitated to refer themselves to be tested for Covid-19.

3. The third issue is quite popular in the daily news. What if the virus mutates and renders itself 'immune' to the vaccine? Some new strains have come up worldwide, and expectedly, the diaspora has started panicking. People need answers quickly while science takes time. So we cannot rule out the possibility that the virus devises a way to escape from the vaccine-induced immunological response. 

4. Vaccine-associated enhanced disease (VAED). Earlier preclinical studies with SARS and MERS have demonstrated that low-level neutralizing antibodies in the plasma can trigger a severe form of the disease. Both the Moderna and Pfizer vaccines are 100% effective in protecting against severe Covid-19, notwithstanding this fact, the regulatory authorities should monitor these and other vaccine candidates for this adverse event. 

5. Anti-Vaxxers! The anti-vaccine sentiment is appalling, and there have been 'anti-vaccine' protests in many parts of the world, including the US, Germany, Poland, and others. There are numerous fake news and misinformation in social media platforms that misguide people and tarnish their perspective about the vaccines. And this phenomenon has even affected the medical professionals. The healthcare authorities have an onerous task to incite confidence in the general public and safeguard them from misinformation. 


Safety

The adverse effect profile of both the vaccines is similar, with the most common being local injection-site reactions. Systemic side effects are more common in the vaccine group and comprise mainly of fatigue and headache. Bell's palsy occurred in three (out of 15,210) vaccine recipients within 28 days of administration. This anecdotal risk would be studied in the planned two-year follow-up. 


Being a physician in the Indian subcontinent, there are various reasons to mistrust this vaccine. Both the mRNA vaccines have been studied primarily in the US population (mainly whites), and we don't have any data on its long-term effects. Recently, I have come across various tweets and posts in my social media feed with the headline - " Doctors and nurses are declining the vaccine." I am unaware of these posts' credibility; however, this isn't false in my experience. Well for what it's worth, we haven't seen a whole lot of polio, diphtheria or smallpox recently. 

Thanks for reading!


-VM


 

 

Sunday, December 20, 2020

The BNT162b2 Covid-19 Vaccine: Pfizer-BioNTech Vaccine

 

The BNT162b2 mRNA Covid-19 vaccine, popularly known as the Pfizer vaccine is the first Covid-19 vaccine to receive authorization for use in the general public. The first jab was given to a 90-year old lady in the UK on December 8, 2020; a monumental event that brought hope to billions of people all across the globe. In this article, I will discuss this vaccine’s clinical trial and potential future implications.

 

How does it act?

The BNT162B2 is a lipid nanoparticle-formulated, nucleoside-modified mRNA that encodes the SARS-CoV-2 full-length spike protein, modified by two proline mutations to lock it in the prefusion conformation. This means that this is an mRNA that has been modified to resist disintegration by nucleases and that translates into the SARS-CoV-2 spike protein. However, this spike protein has also been modified to lock it into its pre-fusion conformation; so that it doesn’t fuse with the target cell’s plasma membrane and remain exposed to immunogenic stimulation.

 

Who is it for?

This primarily depends on the characteristics of the population included in the vaccine’s clinical trial. This trial randomised 43,458 persons from six countries: USA, Argentina, Brazil, South Africa, Germany, and Turkey. More than three-fourth of the study population (76.7%) belonged to the USA. Moving on to the representation of race or ethnicity in the study population - 82.9% were white, 27.9% were Hispanic, while African Americans, Asians, and Native Americans comprised 9.2%, 4.2%, and 0.5% of the study group. Males and females were almost equally included. The age range is from 16 years to 89 years in the intervention group. This trial did not evaluate the efficacy of the vaccine in children, adolescents, and pregnant women.  

 

Is it effective?

Define effective; it depends on the trial’s efficacy end points. The primary endpoint was the efficacy of the vaccine to prevent Covid-19 infection 7 days after the second dose in participants who had no serologic (antigen and antibodies) or virologic (RT-PCR) evidence of SARS-CoV-2 infection up to 7 days after the second dose; the second primary endpoint was to prevent infection in those with and without evidence of prior infection. Confirmed Covid-19 was defined as – the presence of at least one symptom (fever, new or worsened cough, new or worsened dyspnoea, chills, new or worsened muscle pain, new loss of taste or smell, sore throat, diarrhoea or vomiting combined with a positive RT-PCR test within 4 days).    

 

 

Efficacy End Point

 

BNT162b2 Group

 

Placebo Group

Vaccine efficacy, % (95% credible interval)

Covid-19 Cases

N

Covid-19 Cases

N

1st Primary

8

18,198

162

18,325

95(90.3-97.6)

2nd Primary

9

19,965

169

20,172

94.6(89.9-97.3

 This trial showed that a two-dose regimen of BNT162b2 (30 micrograms per dose, given 21 days apart) was 95% effective in preventing symptomatic Covid-19 infection 7 days after its course. The efficacy was 52% after the first dose, and 91% in the first 7 days after the second dose.

However, the trial results did not show the efficacy in preventing asymptomatic infection. We don’t know if this vaccine can safeguard against transmissible asymptomatic infection; therefore, people who have taken the vaccine should not stop wearing masks for the sake of the people around them.

 

Is it safe?

The vaccine group reported more local reactions, such as pain, redness, and swelling at the injection site than the placebo group. In general, these were mild-to-moderate in severity and resolved within 1-2 days. The systemic adverse effects were also reported more in the intervention group, especially in the younger population (16 to 55 years of age), and more after the second dose. These included – fever (11%), fatigue (51%), headache (39%), chills (23%), muscle pain (29%), joint pain (19%), and 38% of the vaccine group needed to use antipyretic medication. These were generally mild and resolved within 1-2 days. Two deaths happened in the vaccine group, one from arteriosclerosis, and one from cardiac arrest. These deaths weren’t related to the vaccine or Covid-19. The investigators plan to continue the surveillance for adverse events for further 2 years.  

 

This study has importance beyond the efficacy of the BNT162b2 vaccine candidate. It demonstrates the utility of RNA-based vaccines, its speed of development, and its promising efficacy in preventing infectious diseases. The success of this clinical trial immensely improves our preparedness for a future pandemic.


Reference:

Polack, FP, et al. Safety and Efficacy of the BNT162b2 mRNA Covid-19 Vaccine. New England Journal of Medicine. Dec 10, 2020. 10.1056/NEJMoa2034577. C4591001 Clinical Trial group


-Vinayak

Tuesday, December 15, 2020

COVID-19 Vaccine Development

The worldwide magnitude of the COVID-19 pandemic is ineffable; it is unsurprisingly compared to the Spanish flu pandemic, which ravaged the world during the First World War (adding fuel to the fire!). One of the pandemic's various positive impacts has been the unprecedented research collaboration and data sharing across the world. Such singular efforts made it possible to cut down the usual time to achieve an approved vaccine from 10+ years to less than a year.

To put things into perspective, it took 60 years from the time of the first polio outbreak to developing its vaccine; in the case of Ebola, it took 15 years. Vaccine candidates for SARS-CoV-1 and MERS did not receive the necessary impetus to advance into fruition. However, with SARS-CoV-2, the situation is very different. Global initiatives such as ACTIV (Accelerating COVID-19 Therapeutic Interventions and Vaccines), a public-private partnership comprising of bigwigs like CDC, FDA, EMA (European Medicines Agency), and numerous leading biopharmaceutical enterprises. Another project on a similar scale is Operation Warp Speed, which has invited comparison to the infamous Manhattan Project.

What is an "ideal" COVID-19 vaccine? There are three criteria from the immunological perspective: 1) It induces a robust humoral immune response that produces long-lasting neutralizing antibodies against SARS-CoV-2 antigens, 2) It generates a strong cell-mediated immunity that includes the production of memory T cells, 3) It should be free of any serious local or systemic adverse effects. Considering the logistics of vaccinating the entire world, there are three more criteria: 1) It should be easy to administer, preferably in one or two doses, 2) It should be easy to produce on a large-scale, 3) Its storage should be uncomplicated, ideally possible at room temperature.


 Source: Front. Pharmacol., 19 June 2020 | https://doi.org/10.3389/fphar.2020.00937

Let us discuss the vaccines that are currently in development. We all have heard about a few of them in the news and social media, namely, Pfizer, Moderna, Covaxin, Astra Zeneca, and so on. There are, impressively, 125+ SARS-CoV-2 vaccines in development globally. Broadly, there are six platforms currently being utilized for vaccine development –

1.   DNA

2.   mRNA (examples – Moderna, Pfizer)

3.   Protein (Subunit vaccines)

4.   Viral vector – replicating/non-replicating (examples - Oxford/Astra Zeneca, Johnson & Johnson)

5.   Live attenuated virus

6.   Inactivated virus

Almost all of the above models have targeted the spike glycoprotein, which is present on the surface of SARS-CoV-2, to interfere with the viral entry into a cell.

This article is an oversimplified summary of the vaccine development process. I haven't covered the vaccine platforms, molecular targets, and vaccine candidates in detail. With the advent of vaccine administration, whether it's Pfizer's or any other, there will be a massive surge in vaccine-related information. There will be challenges at every step, from distribution to underdeveloped areas of the world to alleviate the concerns of the skeptical anti-vaxxers. Let us hope that these vaccines start the end of the pandemic.

-Vinayak

Saturday, December 12, 2020

About the Pfizer BioNTech COVID-19 Vaccine trial

Important things we know about the Pfizer BioNTech COVID-19 Vaccine

• From roughly 44000 participants, vaccine and placebo were administered 1:1 ratio, the vaccine participants demonstrated 95% efficacy in preventing COVID-19 in those without prior infection 7 days or more after the second dose.

• Partial protection from the vaccine candidate appeared as early as 12 days after the first dose.

• The vaccine has shown consistent results in people of different ages, races, BMI, and with various co-morbid conditions.

Pediatrics Allergy & Immunology UWorld Step 2 CK

 

Saturday, June 27, 2020

Post BCG injection site reaction

Hello Awesomites!


Today,the mother came with one week 5 day old newborn. She noticed a papule in left upper arm of newborn. She was afraid and thus visited the OPD.On history, the child was vaccinated on day 0 . So we counselled her as it was Post-BCG Vaccination injection site reaction characterized by a papule, which may be red, tender and indurated. The papule commences two or more weeks after vaccination and then may progress to become ulcerated healing after 2-5 months leaving a superficial scar.


I forgot to take picture due to rush. You can google the pictures.

-Upasana Y. 

Wednesday, April 15, 2020

Clinical pearl : TNF-alpha therapy

Hello

In case of granulomatous diseases, macrophages activated by Th1 cells lead to increased levels of TNF-alpha. Now, TNF-alpha induces and maintains granuloma formation. Basic, right?

So we give anti-TNF drugs (adalimumab, infliximab, etc.). However, they cause the granuloma to break down, thus leading to disseminated disease.

Bottom line - Always remember to check for the presence of latent TB before starting anti-TNF therapy.

That's all
- Jaskunwar Singh

Friday, April 3, 2020

COVID-19: Trained immunity from BCG vaccine

Would BCG vaccination really help in immunizing up against SARS-CoV-2?


Let's dig in. 

BCG is a live-attenuated strain derived from an isolate of Mycobacterium bovis used widely across the world as a vaccine for tuberculosis (TB). But that's not all, BCG vaccination is a potential goldmine against so many diseases.

COVID-19: Hydroxychloroquine mechanism and role in management of SARS-CoV-2 infection

Hello everyone, this post aims to highlight all the important aspects of the recently famous drug hydroxychloroquine in the management of COVID-19.

Mechanism of action: In a study by Aartjan et al, zinc ions (Zn2+) in high intracellular concentrations have been shown to inhibit viral RNA polymerase. However, zinc being an ion cannot enter the cell through the plasma membrane, so it needs ionophores such as pyrithione (PT) to enter the cell, where, in high concentrations, it can efficiently impair the replication of a variety of RNA viruses. Chloroquine can also act as an ionophore that can increase zinc ions transport into the cell.
According to Harrison’s principles of internal medicine, “Infection of tissue culture cells by viruses such as Semliki Forest virus, vesicular stomatitis virus, and certain strains of influenza virus can be prevented by chloroquine, an agent that blocks the function of lysosomes. Chloroquine is a weak base that diffuses into lysosomes and becomes protonated, raiding the pH and ionic strength of the lysosome. When the pH rises, the lysosomal enzymes fail to function. Viruses that require acid pH to fuse with cell membranes can no longer do so in the presence of chloroquine, and the cells are protected from infection.”

Studies revealed that it also has potential broad-spectrum antiviral activities by increasing endosomal pH required for virus/cell fusion, as well as interfering with the glycosylation of cellular receptors of SARS-CoV. The anti-viral and anti-inflammatory activities of chloroquine may account for its potent efficacy in treating patients with COVID-19 pneumonia.

Chloroquine can also prevent orf1ab, ORF3a, and ORF10 from attacking the heme to form the porphyrin and inhibit the binding of ORF8 and surface glycoproteins to porphyrins to a certain extent, effectively relieving the symptoms of respiratory distress. The infectivity of the nCoV pneumonia was not completely prevented by the drugs, because the binding of E2 glycoprotein and porphyrin was not inhibited. You can read more about this on our previous post on: Coronavirus and hemoglobin https://www.medicowesome.com/2020/04/covid-19-coronavirus-and-hemoglobin.html


Current place in the management of COVID-19


1. In India, ICMR has recommended this drug for prophylaxis to healthcare workers dealing with infected patients and asymptomatic contacts of infected people at a dose of 400 mg per week. Besides AIIMS(New Delhi) has recommended this drug for the treatment of moderate to severe cases who are admitted in the hospital at a dose of 400 mg BD for 1 day which is followed by 200 mg BD for 5 days.

2. Chen et al in an unpublished RCT of 30 patients did not find HCQ provided benefit. The study suggests that if it has an impact, it is likely small. 

3. Gautret et al in a non-RCT of 36 patients suggested that HCQ reduced the duration of viral shedding in infected patients. 6 patients in a post-hoc analysis who received HCQ in combination with azithromycin showed further reduction in the viral carriage. However, this was not statistically significant and groups were not well balanced at baseline. 

4.  Chen et al in a double-blind RCT of 62 patients showed that HCQ can significantly shorten the time to clinical recovery and promote the absorption of pneumonia among patients with COVID-19. However, this study has not yet been certified by peer review. 

5. The Marseille study, an unblinded, non-randomized study of 26 infected patients showed a significant reduction in viral load with HCQ. And the number of positive cases was spectacularly reduced by the combination of HCQ with azithromycin. However, this study was full of flaws, there wasn’t adequate matching between the two groups, there were 6 dropouts who weren’t accounted in the study, patients in the control group didn’t have uniform testing, and the patients in the HCQ group had more severe symptoms and were further along in their clinical course. Apparently, this was the study, based on which President Trump promoted the use of HCQ!

6. The patients taking HCQ should be closely monitored for toxicity, in particular, QT prolongation; especially if it is used with azithromycin. Combining lopinavir/ritonavir with HCQ or chloroquine can cause serious arrhythmias and drug interactions due to the increased QT interval. 


Effect of the pandemic on drug supplies for Rheumatology patients


Hydroxychloroquine has been in use since the 1940s for the treatment of rheumatological conditions such as RA, SLE, and Sj√∂gren’s syndrome. The sudden interest in this drug has led to shortages for patients who rely on it for the treatment of their autoimmune conditions. The Lupus Foundation of America has called on drug manufacturers to increase the production of HCQ, in order to ensure that patients with SLE are still able to access it without much difficulty.

Overall, no agent has proven efficacy for COVID-19. A number of approaches are being investigated based on in vitro or extrapolated evidence, including remdesivir, hydroxychloroquine, chloroquine, interleukin-6 pathway inhibitors, and convalescent plasma. When treatment of COVID-19 is being considered, patients should be referred to a clinical trial whenever possible. A registry of international clinical trials can be found at clinicaltrials.gov. 

Thank you! :) 

-Vinayak

References:
1. CHEN J. ,LIU D. et al. A pilot study of hydroxychloroquine in treatment of patients with common coronavirus disease-19 (COVID-19). J Zhejiang Univ (Med Sci), 2020, 49(1): 0-0.
2. Gautret P, Lagier JC, Parola P, et al. Hydroxychloroquine and azithromycin as a treatment of COVID-19: results of an open-label non-randomized clinical trial. Int J Antimicrob Agents. 2020. [PMID:32205204]
3. Wang M, Cao R, Zhang L, et al. Remdesivir and chloroquine effectively inhibit the recently emerged novel coronavirus (2019-nCoV) in vitro. Cell Res. 2020. [PMID:32020029]
4. Efficacy of hydroxychloroquine in patients with COVID-19: results of a randomized clinical trial. Zhaowei Chen, Jijia Hu, et al. medRxiv 2020.03.22.20040758; doi: https://doi.org/10.1101/2020.03.22.20040758
5.te Velthuis AJ, et al. Zn(2+) inhibits coronavirus and arterivirus RNA polymerase activity in vitro and zinc ionophores block the replication of these viruses in cell culture. PLoS
Pathog. 2010 Nov 4;6(11):e1001176. doi: 10.1371/journal.ppat.1001176. PubMed
PMID: 21079686; PubMed Central PMCID: PMC2973827.

Sunday, December 29, 2019

Mnemonic for Antibodies in SLE & it's Clinical Importance

Hi everyone!

Here is a hack.

ANA = All Negative Absent = All Positive identified = Highest Sensitivity ( So best Screening Test ) 

Anti dsDNA = Disease Severity 

Anti Sm = Specific Most

Anti RNP = Raynaud & Polymyositis ( MCTD )

Sunday, November 10, 2019

Multiple Myeloma notes and mnemonics

Hi!

Multiple myeloma - everything P


- malignant Proliferation of Plasma cells derived from a single clone.
- Immunoglobulin produced is a "ParaProtein" (M- protein)
- POEMS syndrome

BONE MARROW INVOLVEMENT
- Pancytopenia

PERIPHERAL BLOOD
- plasma cell leukemia ( greater than 2,000 per mm3 )

BONE INVOLVEMENT
- punched-out lesions in radiographs of flat bones
- bone pain
- pathological fractures

RENAL INVOLVEMENT
- Bence -Jones proteinuria
- production of excess Amyloid protein
- hyPer- calci -emia and -uria

These three result in renal damage and renal failure.

IMMUNE SYSTEM INVOLVEMENT
- prone to infections, particularly in respiratory and urinary tract.

HYPERVISCOSITY SYNDROME
( mnemonic - HPRVSCST )
- Headache
- Postural hypotension
- Retinal venous congestion
- Vertigo
- Strain (blurred vision)
- Congestive cardiac failure
- subtype IgA
- nysTagmus

CLOTTING PROBLEMS
- purpura
- profuse bleeding ( epistaxis, gastrointestinal )

NEUROLOGICAL MANIFESTATIONS
- peripheral neuropathy
- compressive myopathy
- carpal tunnel syndrome ( nerve entrapment)
- Amyloidosis.

SERUM STUDIES
- total serum protein raised
- low albumin
- high globulin ( decreased A:G ratio )
- high beta-2 microglobulin ( greater than 5.5 mg/dL means poor prognosis; stage III)

Plasmacytomas in Paraskeletal soft tissues - poor prognosis; treated by palliative radiotherapy.


That's all
Anything more to add, you're most welcome :)
- Jaskunwar Singh

Monday, July 22, 2019

Anterior chamber associated immune deviation

Some specific antigens when placed in the anterior chamber of the eye result in a suppression of cell mediated immunity, with a normal humoral component.

There is something known as the ' oculo splenic axis' , whereby the antigens travel via the trabecular meshwork and reach the spleen. In the spleen, they secrete MIP 2 which attracts the NK cells. The NK cells in turn secrete IL10 and TGF beta. The T cells in this environment become regulatory cells and suppress the cell mediated immunity. Production of IL2 is suppressed.

The eye is an immuno privileged organ, as it needs to be structurally maintained pristine to preserve it's light carrying capability. ACAID is a mechanism by which Nature attempts to limit unwanted inflammatory responses in the anterior chamber.

It has implications in intraocular tumors, autoimmune, and infectious immune responses.

-Sushrut

PS- The failure of ACAID in the mechanism of lens induced uveitis still remains unexplained!

Friday, June 21, 2019

What are APS?

APS or Autoimmune Polyendocrine Syndromes are exactly what the name suggests.
They’re autoimmune in origin and they attack more than one endocrine system.


[Please click on the image to enhance it]

Let’s not forget autoimmunity begets autoimmunity.
APS are commonly seen with hypogonadism, vitiligo, alopecia, pernicious anaemia and coeliac disease, among others.


That’d be all. Happy studying!
- Ashish Singh.

Thursday, May 16, 2019

Hook effect of prolactin in large pituitary adenomas

Hello everyone,

Here's something I learnt today when a case of large pituitary adenoma causing visual field loss was presented today.

But let's talk about my favorite subject first - Immunology!

The intensity of an antigen-antibody interaction depends primarily on the relative proportion of the antigen and the antibody. A relative excess of either will impair adequate immune complex formation. This is called the “high-dose hook effect” or the “prozone phenomenon.”

This is important consideration whe measuring prolactin. Extremely high levels of prolactin can interfere with the assay and produce falsely low readings.

This high-dose hook effect occurs because there is not enough antibody to bind to both ends of all antigenic peptides, in this case, prolactin.

Most prolactin is complexed to a single antibody. Only few remaining prolactin peptides are “sandwiched” and therefore detectable.

This results in a falsely low prolactin value.

Hence, as the antigen concentrations increase, there is a proportional increase in assay titers up to a certain level. Antigen concentrations above this threshold level would “hook” down the assay values resulting in very low measurements.

In order to avoid the high-dose hook effect, the serum prolactin should be estimated in appropriate dilution in all patients with large pituitary tumors.

-IkaN (tired Internal Medicine Resident)

Source:
The 'hook effect' on serum prolactin estimation in a patient with macroprolactinoma. https://www.ncbi.nlm.nih.gov/m/pubmed/11303248/