Thanks for that. Wonder if anyone  has come across data on collecting a single 24 hr. urine in thymol, taking an aliquot for urate and acidifying the rest for other chemistries?

 

Bw

 

A

 

 

 

[log in to unmask]

 

Hi Nicola

 

WEQAS have carried out extensive work on the acidification of urine calcium.  We undertook a survey a few years ago which showed a large variation in practice. 

 

We provide pre-acidified urine samples for calcium, magnesium and phosphate analysis on the WEQAS Urine Chemistry scheme.  Our acidification procedure is suitable for all methods.  Lower inter-laboratory variation is observed with acidified samples and we have demonstrated that acidified samples have improved stability which is essential for EQA.

 

If you would like any further info please do not hesitate to contact me.

 

Best regards

 

Gareth

 

 

 

 

Thank you to the people that replied to my mail-base post earlier this week. There is definitely not a standardised procedure for collection/lab processing of urine samples for calcium analysis (see my summary below).

 

Laboratory	24h urine calcium procedure	Spot urine calcium procedure	Reference
A	Plain bottles, do not acidify, analyse within 24h	Plain bottles, do not acidify, analyse within 24h	Sodi et al Ann Clin Biochem 2009
B	Plain bottles, do not acidify, reject samples if received when >48h old	Plain bottles, do not acidify, reject samples if received when >48h old	Sodi et al Ann Clin Biochem 2009
C	Acid bottles containing 25mL of 5M HCl and check pH <3 before analysis	Acidify in lab - add 20uL of 25% HCl for every 2mL of sample, mix and stand overnight before analysis.	Not stated
D	Acid bottles with 50ml of 4M HCl	Not stated	Not stated
E	Acid bottles	Acidify in lab	Not stated
F	Acidify in lab to pH 3, allow to stand for 1h	Acidify in lab to pH 3, allow to stand for 1h	Hg et al Clin Chem 1984
G	Acidify in lab to pH 1.5 using 12 mol/L HCl	Acidify in lab to pH 1.5 using 12 mol/L HCl (stated this is especially necessary if stored refrigerated)	Hg et al Clin Chem 1984

 

So does it really make a difference? One lab stated that they have a constant positive bias of 0.3 mmol/L on their EQA scheme and wonder if this could be caused by other labs in their method group  not acidifying samples.

 

Finlay, is this something that UKNEQAS could help get to the bottom of?

 

Best wishes,

 

Nicola Pullan

Principal Clinical Biochemist

Pathology Department (Biochemistry)

Royal United Hospital Bath NHS Trust

Combe Park

BATH

BA1 3NG

 

Tel: 01225 824711

 

Email: [log in to unmask]

 

 

 

 

 

-----Original Message-----
From: Clinical biochemistry discussion list [mailto:[log in to unmask]] On Behalf Of Pullan Nicola (ROYAL UNITED HOSPITAL BATH NHS TRUST - RD1)
Sent: 11 August 2014 11:43
To: [log in to unmask]
Subject: Urine calcium acidfication

 

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This message was sent from an email address external to NHSmail but gives the appearance of being from an NHSmail (@nhs.net) address. The recipient should verify the sender and content before acting upon information contained within.

 

The identified sender is [log in to unmask]

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Dear Mailbase,

 

How may labs currently ask for 24h urine samples for calcium to be collected in acid?

 

If you don't ask for collection in acid - do you acidify before analysis? If so, which acid and concentration do you use/to what pH? And how long do you leave the acidified sample before analysis?

 

What are your procedures for spot urine samples for calcium analysis?

 

Best wishes,

 

Nicola

 

 

Nicola Pullan

Principal Clinical Biochemist

Pathology Department (Biochemistry)

Royal United Hospital Bath NHS Trust

Combe Park

BATH

BA1 3NG

 

Tel: 01225 824711

 

Email: [log in to unmask]

 

 

 

 

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